CIRCUIT DESIGN MU-4-434 User manual

OG_MU-4-434_v10e
OPERATION GUIDE
Embedded low power radio modem
MU-4-434
434MHz
Operation Guide
Version 1.0 (Sept. 2020)
CIRCUIT DESIGN, INC.,
7557-1 Hotaka, Azumino
Nagano 399-8303, JAPAN
Tel: [phone]
Fax: [phone]
E-mail: [email protected]
Web site: http://www.circuitdesign.jp

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OPERATION GUIDE
Contents
Chapter 1 The MU-4 .................................................................................................................................................. 4
1.1 Outline ................................................................................................................................................................. 4
1.1.1 Features ....................................................................................................................................................... 4
1.1.2 Applications .................................................................................................................................................. 4
1.2 Block Diagram ..................................................................................................................................................... 5
1.3 Example of the Control Method .......................................................................................................................... 6
1.3.1 Example 1: Controlling the MU-4 with the on-board CPU ............................................................................ 6
1.3.2 Example 2: Controlling the MU-4 via RS232C ............................................................................................. 6
Chapter 2 Specifications and Diagram ......................................................................................................................... 7
2.1 Main Specifications ............................................................................................................................................. 7
2.1.1 General specifications .................................................................................................................................. 7
2.1.2 UART interface specifications ...................................................................................................................... 7
2.2 Terminal Specifications ........................................................................................................................................ 8
2.3 Channel Table ................................................................................................................................................... 10
2.4 Dimensional Drawing ........................................................................................................................................ 12
2.4.1 External dimensions ................................................................................................................................... 12
2.4.2 Diagram of dimensions for hole positions .................................................................................................. 12
Chapter 3 How to Design a User System ................................................................................................................... 13
3.1 Circuit Board Design ......................................................................................................................................... 13
3.2 Miscellaneous ................................................................................................................................................... 14
Chapter 4 How to Use the MU-4................................................................................................................................. 15
4.1 Communication Concept ................................................................................................................................... 15
4.1.1 Station types and link parameters .............................................................................................................. 15
4.1.2 Basic data transmission.............................................................................................................................. 16
4.1.3 The data transmit command ....................................................................................................................... 17
4.1.4 The link parameters .................................................................................................................................... 18
4.1.5 Conditions for establishing a link ................................................................................................................ 18
4.2 System Configuration (When the Relay Function is Not Used) ........................................................................ 19
4.2.1 Communication within a group (1:N and N:N systems) ............................................................................. 19
4.3 System Configuration (When the Relay Function is Used) ............................................................................... 20
4.3.1 Transmission with the route register route information .............................................................................. 20
4.3.2 Transmission with the route information entered in the transmit command ............................................... 20
4.3.3 1:N relay system ......................................................................................................................................... 21
4.4 Modes ................................................................................................................................................................. 22
4.4.1 Command mode ......................................................................................................................................... 22
4.4.2 Text mode (for testing) ................................................................................................................................ 22
4.4.3 Binary mode (for testing) ............................................................................................................................ 22
4.4.4 Mode setting ............................................................................................................................................... 23
4.5 Resetting ........................................................................................................................................................... 24
4.6 Initializing........................................................................................................................................................... 24
4.7 Changing Channels ........................................................................................................................................... 24
4.8 Standby Mode ................................................................................................................................................... 24
4.9 Antenna Power Setting ...................................................................................................................................... 25
4.10 Communication Protocols ............................................................................................................................... 25
Chapter 5 Commands, Responses and Receives ................................................................................................... 26
5.1 About the Command, Response and Receive .................................................................................................. 26
5.2 Command, Response and Receive Table ......................................................................................................... 30
5.2.1 Data transmit commands and data transmit responses ............................................................................. 30
5.2.2 Data receives .............................................................................................................................................. 30
5.2.3 Control commands and control responses ................................................................................................. 31
5.2.4 Monitor commands and monitor responses ............................................................................................... 31
5.2.5 Test commands and test responses ........................................................................................................... 32
5.2.6 Extended commands and extended responses ......................................................................................... 32
5.2.7 Receive response ....................................................................................................................................... 32
5.2.8 ACK response ............................................................................................................................................. 32
5.2.9 Error response ............................................................................................................................................ 32
5.3 Save Setting Command Options ....................................................................................................................... 33
5.4 Command, Response and Receive details ....................................................................................................... 34
5.4.1 Data transmit commands, responses and data receives ................................................................
................................

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OPERATION GUIDE
5.4.2 Control commands and control responses ................................................................................................. 42
5.4.3 Monitor commands and Responses ........................................................................................................... 49
5.4.4 Test commands and Responses ................................................................................................................ 52
5.4.5 Extended command and extended response ............................................................................................. 54
5.4.6 Receive response ....................................................................................................................................... 58
5.4.7 ACK response ............................................................................................................................................. 58
5.4.8 Error response ............................................................................................................................................ 58
Chapter 6 How to Develop a Program ........................................................................................................................ 60
6.1 Outline of User Processes ................................................................................................................................ 60
6.2 The Operations of the MU-4 .............................................................................................................................. 61
6.3 Command Transmission ................................................................................................................................... 62
6.3.1 Issuing commands ...................................................................................................................................... 62
6.3.2 Issuing data transmit commands ................................................................................................................ 62
6.3.3 Issuing commands continuously ................................................................................................................ 63
6.3.4 Issuing commands continuously (when ignoring the response)................................................................. 63
6.4 Response and Receive Processing .................................................................................................................. 64
6.4.1 Responses and receives ............................................................................................................................ 64
6.4.2 Response and receive formats ................................................................................................................... 64
6.4.3 Response and receive types ...................................................................................................................... 64
6.4.4 Response and receive processing ............................................................................................................. 65
6.5 Creating an Air Monitoring Function .................................................................................................................. 67
6.6 Assessing the Field Status for Communication ................................................................................................. 67
6.6.1 Source station RSSI measurement ............................................................................................................ 67
6.6.2 Target station RSSI measurement.............................................................................................................. 68
6.6.3 Packet test .................................................................................................................................................. 68
6.7 Achieving Data Transmission ............................................................................................................................ 68
6.8 Operation in Binary Mode ................................................................................................................................. 69
6.8.1 Modes ......................................................................................................................................................... 69
6.8.2 When developing a new system ................................................................................................................. 70
6.8.3 When using only the data line of existing equipment ................................................................................. 71
6.8.4 Conditions for use of the binary mode ........................................................................................................ 71
6.9 Error Correction Function .................................................................................................................................. 72
Chapter 7 Timing ........................................................................................................................................................ 73
Chapter 8 Transparent mode ...................................................................................................................................... 79
8.1 Transparent mode setting ............................................................................................................................... 79
8.2 Data transmission and reception .................................................................................................................... 79
8.3 Commands valid for transparent mode .......................................................................................................... 80
8.3.1 Commands which can be used in the transparent mode (when @TR ON is issued) ............................. 80
8.3.2 Commands which cannot be used in the transparent mode (when @TR ON is issued) ........................ 80
8.4 Timing for ‘@TR‘ command ............................................................................................................................ 81
8.5 Data format ........................................................................................................................................................ 83
8.5.1 Data frame structure ................................................................................................................................ 83
8.5.2 Data synchronization using UART ........................................................................................................... 84
Chapter 9 Miscellaneous ............................................................................................................................................ 85
9.1 The MU-4 Evaluation Program ....................................................................................................................... 85
Chapter 10 Regulatory Compliance ........................................................................................................................... 86

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OPERATION GUIDE
Chapter 1 The MU-4
1.1 Outline
The MU-4 is an embedded low power radio modem for transmission of serial data. Since it is possible to control the
radio component using dedicated simple commands, the user can concentrate on developing the transmitting and
receiving programs for their system. For communication protocols, the MU-4 has a standard protocol common to
Circuit Design’s MU series and an error correction protocol which performs error correction on the receiver side.
Since the error correction protocol uses Reed-Solomon code*1 that has strong error correction ability even in
environments prone to burst errors, the user can configure highly reliable systems compared to conventional radio
modems. Transmitting and receiving data and issuing commands are performed using a UART*2 interface with a
single-chip CPU and the modem can also be controlled via the COM port (RS232C format) of the computer, making
it possible for the user to develop systems quickly*3.
In addition, using a maximum of 10 relay stations, it is possible to gather data from and control equipment in remote
locations. The MU-4 is designed to minimize design difficulties involving high frequency components, so that the
user can embed the modem in their system with peace of mind.
 Important
It is not possible simply to replace communication using existing RS232C system equipment connected
with a cable, with MU-4 wireless communication. In order to build wireless systems, issues specific to
radio communications must be solved. The hardware and software must be newly designed specifically
for the MU-4.
*1 Forward error correction code used for compact discs, hard disks and satellite communications
*2 UART (Universal Asynchronous Receiver Transmitter)
*3 Development kits such as MU4-RS2(RS232C interface board), MU4-USB(USB interface board) are available
1.1.1 Features
 RED compliant
 RF control and serial data transmission with a simple system of commands
 Strong error correction using Reed-Solomon code
 Long distance communication using a maximum of 10 relay stations
 Communication protocol common to an MU series
 N:N system possible by setting User/Group/Equipment IDs
 Radio and field status assessment using RSSI acquisition commands
 Transparent mode in which user’s own protocol can be used
1.1.2 Applications
 Serial data transmission
Energy monitoring, data monitoring devices, handy terminals, barcode readers, housing equipment control
 Telecontrol
Various warning systems, remote control for construction machinery, display devices, motor control, lifters
Remote control of FA equipment
 Telemetry
Security systems, water level monitors for rivers and dams, temperature and humidity gauges, rain gauges,
pressure gauges, voltmeters, ampere meters

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OPERATION GUIDE
GND 14
RF
Switch
BPF
SAW Filter LNA
BPF
13
VCC Regulator
TCXO
XTAL
EEPROM
SPI,GPIO
TXD
1
RXD
2
RTS
3
CTS
4
MOD(MODE)
5
INI
6
RST(RESET)
7
RXN(RX-MON)
8
RXL(RX-LED)
12
TXL(TX-LED)
11
DO(DATA-OUT)
10
DI(DATA-IN)
9
RXIN
Narrow band
RF IC
TXOUT
CLOCK
T-DATA
7.3728MHz
Control
CPU
CLOCK
TXD
RXD
Port
Port
Port
Port
RESET
Port
Port
Port
Port
2.8V for RF
DVCC for Digital
parts
RF CN
MU-4-434 Block Diagram
25.6MHz
434MHz
1.2 Block Diagram

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OPERATION GUIDE
1.3 Example of the Control Method
The VCC terminal of the MU-4 is connected directly to the power source of the mounted CPU. Ensure that the
voltage of the power supply is regulated to within DC +3.0 v to +5.0 v.
Basically the MU-4 uses hardware flow control with RTS or CTS, however 3-line control can be used without the
hardware flow control. In this case, set the CTS terminal to Low level. In addition, care is required with the timing of
transmitting and receiving.
Example 1 and Example 2 are basically the same methods except for the difference in control voltage.
1.3.1 Example 1: Controlling the MU-4 with the on-board CPU
It is possible to interface the MU-4 directly using the UART interface of the on-board CPU.
1.3.2 Example 2: Controlling the MU-4 via RS232C
1. Using the RS232 port of your computer, you can develop a new program for OS’s such as Windows and the like.
In this case, use an RS232C transceiver. (The program for existing system equipment will not work.)
2. By supplying power to the MU-4 with a cable, you can also isolate the radio component from your system and
locate it in the most suitable environment. The distance can be extended by 15 m to 50 m, but the exact distance
should be confirmed through experiments.
* To use the Evaluation Software Program, the DSR signal line should be set to High level.
* When hardware flow control is not used, connect the RTS and CTS at RS232C level.
RXD
TXD
CTS(Port)
RTS(Port)
Port
User CPU
With UART
Peripheral
Antenna
DC
+
3
.0
v to
+ 5.
0
v
Regulator
+
-
+
3.0
v to
+
5
.0v
DC Power
Tx,
Rx Indicator
MU -4
TXD
1
RXD
2
RTS
3
CTS
4
MOD
5
INI
6
RST
7
RXM
8
RF
14
GND
13
VCC
12
RXL
11
TXL
10
DO
9
DI
User
RS
232
system
1
RXD 2
TXD 3
DTR 4
GND 5
DSR 6
RTS 7
CTS 8
9
1
2 RXD
3 TXD
4 DTR
5 GND
6 DSR
7 RTS
8 CTS
9
D-
Sub
9pin
D -
Sub
9 pin
Straight
cable
RS
232
transceiver
Regulator
+
-
DC
+3
.
0
v to
+ 5.0
v
DC Power
+ 3.0
v to
+ 5.0
v
MU
-
4
Antenna
Tx
,
Rx Ind
icator
TXD
1
RXD
2
RTS
3
CTS
4
MOD
5
INI
6
RST
7
RXM
8
RF
14
GND
13
VCC
12
RXL
11
TXL
10
DO
9
DI

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OPERATION GUIDE
Chapter 2 Specifications and Diagram
2.1 Main Specifications
2.1.1 General specifications
Temperature conditions: +25ºC ± 5ºC, typical
Item Specification Remarks
Compatible standards EN 300 220 CE mark
Emission class F1D
Antenna power (selectable) Within 10 mW or 1 mW +5ºC to +35ºC Contact (50 Ω)
Selectable by the command
Frequency stability Within ± 4 ppm Reference freq. at 25ºC
Antenna 1/4λ wire antenna Gain of 2.14 dBi or less
Communication method Half-duplex, one-way, broadcast
Modulation system Binary FSK
Oscillation system PLL synthesizer system
Radio communication speed 4800 bps
Frequency range 433.2000 to 434.7750 MHz
Channel spacing 12.5 kHz
Number of channels 127 Channel step 12.5 kHz
Receiver spurious radiation -57 dBm or less (<1GHz)
-47 dBm or less (>1GHz)
Receiver sensitivity -113 dBm Transparent mode (BER 0.1%)
Operating temperature -20ºC to +65ºC
(No dew condensation)
The operation distance
varies with the
temperature conditions.
Storage temperature -25ºC to +70ºC
(No dew condensation)
Operating voltage 3.0 V to 5.0 V Absolute maximum rated voltage 5.5 v
Consumption current At 10mW: TX 42 mA RX 22 mA
At 1 mW: TX 26 mA RX 22 mA When the supply voltage is 3 v
Standby mode consumption current 4 mA When the supply voltage is 3 v
Number of EEPROM conversions 1,000,000 times
Error correction system Reed-Solomon code RS (255, 247)
External dimensions 36 mm × 26 mm × 8 mm (W × D × H)
Not including the antenna.
H is the height from the mounting
surface.
Unit weight 14.5 g
Reference data
* Effective radio communication speed: About 3,400 bps / Conditions: One-way communication, no error correction, 25ºC
* Range: About 600 m / Conditions: One-way communication, no error correction, 25ºC, line of sight distance, ground level of 1.5
m, vertical antenna
2.1.2 UART interface specifications
Communication method Serial communication (RS232C format)
Synchronization Start-stop (asynchronous)
Data speed 1,200 / 2,400 / 4,800 / 9,600 / 19,200 / 38,400 / 57,600 bps
Flow control RTS/CTS hardware flow control
Other parameters Data length (8 bits), Parity (None, Even, Odd), Stop bits (1 or 2 )

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OPERATION GUIDE
MU-4 terminal number and name (Top View)
2.2 Terminal Specifications
◇ Level conversion is required for connection to RS232.
The RS232C DSR signal must be supported by the
user's circuit board.
◇ Unused terminals should be set to open.
◇ The thresholds for Low level and High level are VCC ×
0.2 and VCC × 0.8 respectively, based on the supply
voltage VCC.
Terminal
No.
Terminal
name
I/
O
Description Internal circuit
1 TXD O The serial data transmit terminal.
2 RXD I The serial data receive terminal.
3 RTS O
The hardware flow control signal output terminal.
If the internal status is not busy, the status is Low
and data can be received via the RXD terminal. If
the internal status is busy, the status is High and
data cannot be received.
4 CTS I
The hardware flow control signal input terminal.
Determines that the unit is not busy when the
status is Low, and sends data from the TXD
terminal.
Determines that the unit is busy when the status is
High, and does not send data.
5 MOD
(MODE) I
Switches between the command mode, binary
mode, or text mode.
In the command mode when set to High, and the
binary mode or text mode when set to Low.
Terminal
27kΩ
330Ω
Vcc
Terminal
27kΩ
330Ω
Vcc
Terminal
27kΩ
330Ω
Vcc
Terminal
27kΩ
330Ω
Vcc
Terminal
27kΩ
330Ω
Vcc
RXD 2 TXD 1
RF CTS 4 RTS 3
14 GND INI 6 MOD 5
13 VCC RXM 8 RST 7
DO 10 DI 9
RXL 12 TXL 11

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OPERATION GUIDE
Terminal
No.
Terminal
name I/O
Description Internal circuit
6 INI
(INITIALIZE)
I
The terminal for initializing the CPU internal
settings.
The settings are initialized if the power is turned
on in the Low state. The default values are
enabled when the power is switched on again.
7 RST
(RESET) I
The CPU reset terminal.
Setting this terminal to Low level for a period of 1
ms resets the internal CPU.
This should normally be set to open.
8
RXM
(RX-MON) O
A test terminal for monitoring the internal status
with an oscilloscope when receiving data.
Normally this should be open and only be used
by the manufacturer.
9 DI
(DATA-IN) I
Transmission data input terminal in the
transparent mode.
After setting the transparent mode, input the
transmission data of 4800 bps.
Set to open when the transparent mode is not
used.
10 DO
(DATA-OUT)
O
Reception data output terminal in the transparent
mode.
Outputs the received data of 4800 bps.
Set to open when the transparent mode is not
used.
11 TXL
(TX-LED)
O
The terminal for the transmission monitor LED.
On when data is transmitted.
The signal line includes an internal 1 kΩ resistor.
With external resistors, ensure that the LED
current is within 1 mA.
In addition, add a ceramic capacitor of about
100 pF in parallel with the LED.
12 RXL
(RX-LED)
O
The terminal for the receiving monitor LED. On
when valid data is received.
The signal line includes a 1 kΩ internal resistor.
With external resistors, ensure that the LED
current is within 1 mA.
In addition, add a ceramic capacitor of about
100 pF in parallel with the LED.
13 VCC I
The power supply terminal. Provide a regulated
power source with a supply voltage of DC +3.0 V
to +5.0 or less.
Applying a voltage higher than the rating will
damage the semiconductor of the unit.
14 GND I GND
- RF I/O The antenna terminal.
* The terminal specifications may change without prior notice.
Terminal
Terminal
27kΩ
1kΩ
Vcc
Terminal
27kΩ
1kΩ
Vcc
Terminal
27kΩ
330Ω
Vcc
1kΩ
1kΩ
Terminal
27kΩ
330Ω
Vcc
Terminal
27kΩ
330Ω
Vcc
Terminal
47kΩ
1kΩ
Terminal
1kΩ

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OPERATION GUIDE
2.3 Channel Table
The frequency channels that the MU-4 can use are channels 1 to 127 in the 434 MHz band.
To set the channel, use the command format ‘@CH + channel number’.
Example: Set channel 15 as the channel to use.
Specify the channel following ‘@CH’ with 2 ASCII (hexadecimal) characters.
Control command: @CH 0F CRLF
Control response: *CH = 0F CRLF
* : Default channel
Channel Frequency Channel Frequency Channel Frequency
Dec. (Hex) MHz Dec. (Hex) MHz Dec. (Hex) MHz
20(14) 433.4375 40(28) 433.6875
1(01) 433.2000 21(15) 433.4500 41(29) 433.7000
2(02) 433.2125 22(16) 433.4625 42(2A) 433.7125
3(03) 433.2250 23(17) 433.4750 43(2B) 433.7250
4(04) 433.2375 24(18) 433.4875 44(2C) 433.7375
5(05) 433.2500 25(19) 433.5000 45(2D) 433.7500
6(06) 433.2625 26(1A) 433.5125 46(2E) 433.7625
7(07) 433.2750 27(1B) 433.5250 47(2F) 433.7750
8(08) 433.2875 28(1C) 433.5375 48(30) 433.7875
9(09) 433.3000 29(1D) 433.5500 49(31) 433.8000
10(0A) 433.3125 30(1E) 433.5625 50(32) 433.8125
11(0B) 433.3250 31(1F) 433.5750 51(33) 433.8250
12(0C) 433.3375 32(20) 433.5875 52(34) 433.8375
13(0D) 433.3500 33(21) 433.6000 53(35) 433.8500
14(0E) 433.3625 34(22) 433.6125 54(36) 433.8625
15(0F) 433.3750 35(23) 433.6250 55(37) 433.8750
16(10) 433.3875 36(24) 433.6375 56(38) 433.8875
17(11) 433.4000 37(25) 433.6500 57(39) 433.9000
18(12) 433.4125 38(26) 433.6625 58(3A) 433.9125
19(13) 433.4250 39(27) 433.6750 59(3B) 433.9250

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OPERATION GUIDE
* The number of channels which can be used at the same time in the same area is at most 8 to 11 due to the
third-order intermodulation or near-far problem.
* The image frequency occurs at the frequency of ‘receiving frequency - 800kHz’ and may degrade the blocking
characteristics of the MU-4. Please take this into account when making a channel plan.
Channel Frequency Channel Frequency Channel Frequency
Dec. (Hex) MHz Dec. (Hex) MHz Dec. (Hex) MHz
60(3C) 433.9375 85(55) 434.2500 110(6E) 434.5625
61(3D) 433.9500 86(56) 434.2625 111(6F) 434.5750
62(3E) 433.9625 87(57) 434.2750 112(70) 434.5875
63(3F) 433.9750 88(58) 434.2875 113(71) 434.6000
64(40) 433.9875 89(59) 434.3000 114(72) 434.6125
65(41) 434.0000 90(5A) 434.3125 115(73) 434.6250
66(42) 434.0125 91(5B) 434.3250 116(74) 434.6375
67(43) 434.0250 92(5C) 434.3375 117(75) 434.6500
68(44) 434.0375 93(5D) 434.3500 118(76) 434.6625
69(45) 434.0500 94(5E) 434.3625 119(77) 434.6750
70(46) 434.0625 95(5F) 434.3750 120(78) 434.6875
71(47) 434.0750 96(60) 434.3875 121(79) 434.7000
72(48) 434.0875 97(61) 434.4000 122(7A) 434.7125
73(49) 434.1000 98(62) 434.4125 123(7B) 434.7250
74(4A) 434.1125 99(63) 434.4250 124(7C) 434.7375
75(4B) 434.1250 100(64) 434.4375 125(7D) 434.7500
76(4C) 434.1375 101(65) 434.4500 126(7E) 434.7625
77(4D) 434.1500 102(66) 434.4625 127(7F) 434.7750
78(4E) 434.1625 103(67) 434.4750 - -
79(4F) 434.1750 104(68) 434.4875 - -
80(50) 434.1875 105(69) 434.5000 - -
81(51) 434.2000 106(6A) 434.5125 - -
82(52) 434.2125 107(6B) 434.5250 - -
83(53) 434.2250 108(6C) 434.5375 - -
84(54) 434.2375 109(6D) 434.5500 - -

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OPERATION GUIDE
2.4 Dimensional Drawing
2.4.1 External dimensions
2.4.2 Diagram of dimensions for hole positions
T o p vi ew

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OPERATION GUIDE
Chapter 3 How to Design a User System
3.1 Circuit Board Design
When embedding this unit in a user system, pay due attention to the design of the board and case.
1. The power supply used for the MU-4 must be a DC regulated power source, with a voltage span of +3.0 v to
+5.0 v. A current of about 40 mA is required when transmitting. Ensure that the voltage of the MU-4 and user
system CPU are the same.
Although a regulated voltage is supplied to the internal high frequency component, in order to support the
voltages of a variety of user systems, the power supply for the CPU is connected directly to the VCC terminal.
For this reason, care is required to achieve the correct voltage range.
2. Add a 1 kΩ resistor or 0.33 μH inductor to the UART related control signal line. This should be inserted close to
the connector pins.
3. When attaching this unit to a circuit board, use a double sided circuit board if possible. On the top surface of the
board, make a sufficient area beneath the MU-4 for the ground pattern (GND plane), and use the bottom surface
of the board for signal lines.
4. If the MU-4 power supply line is used jointly with the power supply lines of other circuits in the system (such as
the CPU), it may cause malfunctions, and the unit may not perform properly.
For the power supply of the MU-4, always use a separate line from the system power circuit, and install bypass
capacitors at the receiving point.
5. It is possible to directly connect LEDs to the LED terminals, however ensure that the LED current is limited to 1
mA or less.
Blinking of the LEDs may affect communication. It is recommend that ceramic capacitors of about 100 pF are
added in parallel to the LEDs.
6. Do not connect anything to RXM terminal.
7. Make the signal lines to this unit as short as possible.
RXD
TXD
CTS
(
Port
)
RTS
(
Port
)
Port
DC
+3.
0
v to
+ 5. 0v
+
-
+ 3. 0v
to
+ 5. 0v
1k
Ω
220
μ
Ｆ
470
pF
470
pF
ＶＣＣ
ＧＮＤ
470
pF
To user parts
To user parts
GND plane
MU -4
Antenna
TXD
1
RXD
2
RTS
3
CTS
4
MOD
5
INI
6
RST
7
RXM
8
RF
14
GND
13
VCC
12
RXL
11
TXL
10
DO
9
DI
User CPU
With UART
Peripheral
Regulator
DC Power
Tx,
Rx Indicator

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OPERATION GUIDE
3.2 Miscellaneous
1. Devise ways of isolating the MU-4 as far as possible from sources of noise, including from other embedded
equipment.
2. Arrange the MU-4 so that it will not be covered by the operator’s hand or the like.
3. The MU-4 does not have a waterproof structure. If the antenna is located outside the main unit, use a structure
that prevents water droplets from entering the case.

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OPERATION GUIDE
Chapter 4 How to Use the MU-4
4.1 Communication Concept
4.1.1 Station types and link parameters
When performing communication using the MU-4, the source station transmits data towards the target station. If
necessary, it is also possible to relay data using relay stations between the source and target stations. In addition,
to avoid collisions with, and to ensure independence from other systems, it is necessary to set the link parameters
to identify the system and each station.
Group ID 01
Same area
UI = 0055
GI = 01
EI = 01
Group ID 02
Group ID 03
User ID 0055
UI = 0055
GI = 01
EI = 02
UI = 0055
GI = 01
EI = 03
Route information:RT
Destination ID:DI
User ID:UI
Group ID:GI
Equipment ID:EI
Channel:CH CH = 08 CH = 08 CH = 08
RT=02,03
Channel 08
Source station
01
Relay station
02
Target station
03
1. The source station, relay station and target station
• Source station The station that transmits data
• Relay station A station to relay data to the target station. The relay station neither buffers nor resends data but
simply relays it directly to the target station. Setting is possible up to a maximum of 10 relay
stations.
• Target station The station that receives data. The target station outputs the received data to the user controller.
It also sends ACK data and RSSI (received signal level) data to the source station depending on
the command issued from the source station.
2. The link parameter
In order to establish communication between the radio stations, it is necessary first to set the link parameters.
• UI: User ID
An ID given to the MU-4 user for identification of the user.
If all the equipment within the user system is not set to the same User ID, no link will be made.
• GI: Group ID
An ID to identify the group within the user system. Set the same Group ID for all radio stations within the group.
• EI: Equipment ID
An ID given to each unit for identification of each station. The data transmit command transmits data to the
Equipment ID set as the route information or Destination ID
• DI: Destination ID
Specifies the Equipment ID of the target station when no relay station is used in the system.
• RT: Route information
Route information to the target station in the system using relay stations. List the route information in the route
register or transmit a command character string.
• Channel
If all stations in a system are not set to the same channel, no link will be made.

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OPERATION GUIDE
4.1.2 Basic data transmission
When user data is transmitted from the source station towards the target station using data transmit commands,
a character string including the data (data receive) is output from the target station and processed by the program
of the user controller.
Example 1 1:1 (1:N) system not using the relay function
When the source station 5F transmits the 5 bytes of data ‘ABCDE’ to the target station 01
The diagram below shows the case in which the data transmit command 1 is issued.
Example 2 System using the relay function
When the source station 5F transmits the 10 bytes of data ‘0123ABC$#4’ to the target station 8F via relay
stations 01, 02 and 03
With 1:N communication not using relay stations, the route is specified using the Destination ID command ‘@DI’
at the source station. However when relay stations are used, data can be relayed using one of the following.
1. Set the route information in the route register using the ‘@RT’ command to specify the relay route.
2. Enter the route information directly at the end of the data transmit command ‘@DT’.
When performing two-way communication, it is necessary to confirm if the data transmitted from the source
station is received at the target station without error. The MU-4 has a data transmit command that requests the
target station to return the data receive acknowledgment ‘ACK’. The diagram below shows a case in which
relay stations are used and the data transmit command 2 with ACK is issued.
⑧ACK return
・Source station 5F status
④Issue the data transmit command 2
⑤Data transmit response
⑨ACK response from the target station
@DT 0A 0123ABC$#4 /A CRLF
(issued after the delay time has elapsed)
・Target station 8F status
⑦Data receive 2
⑧ACK return
⑤
⑨
⑦User
controller
User
controller
*DT=0A CRLF
*DR=00 CRLF
＊DR=0A 0123ABC$#4 CRLF
⑥Send data
④
⑥Send data
・Initial setting
①Set all stations to the same
User ID, Group ID and channel
②Set a different number to each
equipment as the Equipment ID (EI)
③Set the route information
in the route register of the
source station
Source station
EI=5F
Relay station
EI=01
Relay station
EI=02
Relay station
EI=03
Target station
EI=08F
User
controller
DI=01
⑥Send data
・Initial setting
④Issue the data transmit command 1
⑤Data transmit response
・Target station 01status
User
controller
@DT 05 ABCDE CRLF
＊DT=05 CRLF
＊DR=05 ABCDE CRLF
⑦Data receive 1
④
⑤⑦
⑥Send data
③Set the Destination ID(DI)
①Set all stations to the
same User ID, Group ID and
channel
②Set a different number to
each equipment as the
Equipment ID (EI)
・Source station 5F status
Source station
EI=5F
Target station
EI=01

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OPERATION GUIDE
4.1.3 The data transmit command
The MU-4 has 3 data transmit commands.
1. Data transmit command 1 2. Data transmit command 2 3. Data transmit command 3
The user can freely decide the format for the data part of the data transmit command. Using data transmit
command 3, the received signal level of the received packet data is included at the front of the receiving data (data
receive), which is useful for determining the transmission route and so on.
The same can be done with the data transmit command 2 by setting the ‘@SI’ command.
When actually developing a system program, in addition to the transmission process of the user system data such
as temperature data and display data, it is necessary to perform various controls. By choosing the transmit
command to use depending on the system configuration, it is possible to simplify design of the system protocol and
make an easy-to use program.
1. Data transmit command 1
The most basic transmission command mainly used for 1:1 (1:N) systems not using relay stations.
2. Data transmit command 2
A data transmit command for systems using relay stations. It can also be used for 1:1 (1:N) systems not using
relay stations.
Command option character for data transmit command 2: ‘/’
Target station output characters (Data receive): ‘*DR’
3. Data transmit command 3
A data transmit command for systems using relay stations. It can also be used for 1:1 (1:N) systems not using
relay stations.
The received signal strength (RSSI) of the received packet data is included at the front of the data receive at the
target station.
Command option character for the control transmit command 3: ‘%’
Target station output characters (Data receive): ‘*DC’
With the data transmit commands 2 and 3, the method of command notation on the program is different
depending on the following cases.
1. Transmission based on route information preset in the route register.
2. Transmission based on route information directly entered in the transmit command.
Example: Transmission using data transmit command 3
⑤ACK return
・Source station 5F status
①Issue the data transmit command 3
②Data transmit response
⑥ACK response
Format 2:@DT 0A 0123ABC$#4 %A CRLF
(issued after the relay time has elapsed)
・Target station 8F status
④Data receive 3
⑤ACK return
②
⑥
④User
controller
User
controller
Target
station
EI=8F
Relay
station
EI=03
Relay
station
EI=01
Relay
station
EI=02
Source
station
EI=5F
*DT=0A CRLF
*DC=45 00 CRLF
Format 1:@DT 0A 0123ABC$#4 %A 01,02,03,8F CRLFWhen RI=OF ＊DC=45 0A 0123ABC$#4 CRLF(Default)
When RI=ON ＊DC=45 0A 0123ABC$#4 /R 5F,01,02,03 CRLF
③Send data
①
③Send data
Transmit the 10 bytes (0Ah) of data ‘0123ABC$#4’ to the target station ID = 8F via the relay station IDs = 01,
02, 03. Source station Equipment ID = 5F.
* ‘45h’ at the front indicates the signal level of the received packet. In this case, it is -69 dBm (45h).
For details of the value, refer to the ‘RA’ command.

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OPERATION GUIDE
4.1.4 The link parameters
In order to transmit and receive data, the MU-4 has the following link related parameters.
Link parameters can be specified easily with commands, and they can be changed each time data is sent.
In addition, if the source station, relay station, and target station do not all use the same channel, no link will be
made.
1. UI: User ID, 16-bit, 0000h to FFFEh (0000h is the ID for testing, and FFFFh cannot be used)
The User ID is an ID given to the MU-4 user for identification of the user system. Communication is not
possible unless all equipment within the user system is set with the same User ID. If a user configures
multiple systems, use the Group ID for identification. The User ID setting command is ‘@UI + User ID +
password’. The product default User ID is 0000 and this can be used as it is when no particular User ID is
required. However, we recommend that you set a User ID to prevent radio interference within a given area.
If you require a User ID, please contact Circuit Design, Inc. The 16 User IDs listed in the explanation of User ID
command can be used freely.
2. GI: Group ID, 8-bit, 00h to FFh
The Group ID is an ID to identify the group within the user system. Set the same Group ID for all equipment
within the group. Maintain Group IDs as identification numbers when building other systems. The setting
command is ‘@GI’.
Please contact Circuit Design, Inc. in cases where use of Group IDs is insufficient and you require other User
IDs.
3. EI: Equipment ID, 8-bit, 01h to FFh (FFh is a special operation)
The Equipment ID is an ID for identification of each radio unit. At the source station, enter the Equipment ID of
the target station at the end of the route information or as the Destination ID to which to transmit data.
At the target station, the Destination ID included in the received packets is automatically compared with the local
station EI. The setting command is ‘@EI’.
4. DI: Destination ID, 8-bit, 00h to FFh (00h and FFh are special operations)
This is used to specify the Equipment ID of the target station in a system not using relay stations. The setting
command is ‘@DI’. If 00 (DI = 00h) is specified as the Destination ID and data transmit command 1 is issued, all
equipment within the same group receives the data at the same time, irrespective of the Equipment ID
(Broadcast). If DI = FFh is specified, the data is sent but no station will receive it.
5. RT: Route information
This indicates the route to the target station.
The route information lists the Equipment IDs of the relay stations and the Equipment ID of the target station in
the route register or data transmit command character string. The route information is used with data transmit
commands 2 and 3. There are two ways to transmit data as follows.
 Transmission based on route information set in the route register with the ‘@RT’ command
 Transmission with the route information entered directly in the data transmission command
If only one station is specified in the route information, that station is the target station.
6. Channel
If all stations in a system are not set to the same channel, no link will be made.
4.1.5 Conditions for establishing a link
A link is established for communications when the following conditions are met simultaneously.
1. There are no errors in the received packet
2. The User ID and Group ID match
3. The Equipment ID specified in the route information or Destination ID and the Equipment ID of the target station
match
4. The channel used is the same

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OPERATION GUIDE
4.2 System Configuration (When the Relay Function is Not Used)
The MU-4 can be used for building 1:1, 1:N, and N:N systems. Several systems can be operated within the same
area by separating the channels used.
Equipment IDs from 01h to FEh can be specified, and a maximum of 254 MU-4 units can be connected in 1 group.
With 1:1 (1:N) communication, the Destination ID is specified and data is transmitted with data transmit command 1,
however in this case set the route register to “relay function disabled = ‘NA’” using the ‘@RT’ command.
4.2.1 Communication within a group (1:N and N:N systems)
Set the same User ID and Group ID for one group. If the Destination ID specified at the source station and the
Equipment ID of the target station match, data (data receive) is output from the target station.
The diagram below shows a 1:N system, although it is also possible to build an N:N system in which all the units
have an equal relationship.
UI
EI
EI EI
EI
EI
EI EI
EI
GI=8
EI
EI EI
EI
※All equipment in the system has the same frequency channel.
※Communication is not possible between different Group IDs.
EI
EI EI
EI
GI=1GI=1
GI=1
UI User ID 2bytes
Item name Size
0000-FFFE Set a password
ID value Content
GI Group ID 1byte 00～FF No. 0 to 255
EI Equipment ID 1byte 01～FE No. 1 to 254
※Group ID and Equipment ID can be set freely within the range above.
UI = 0055
GI = 01
EI=02
Source
station
Target
station
Target
station
Target
station
UI = 0055
GI = 01
EI=03
UI = 0055
GI = 01
EI=04
UI = 0055
GI = 01
EI=01
Group1 (1:N system)
Same area
Group2 (1:N system)
Group3 (1:N system)
DI=01
DI=02
DI=03
DI=01
DI=04
DI=01
Note: UI = User ID, GI = Group ID, EI = Equipment ID, DI = Destination ID, RT = Route information
 Communication between groups
By changing the Group ID for transmitting, it is possible to communicate with another group.
 Broadcast communication
If the Destination ID is specified as 00h at the source station and data is transmitted, all target stations will receive
the data at the same time, irrespective of the Equipment ID.

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OPERATION GUIDE
4.3 System Configuration (When the Relay Function is Used)
With 1 hop communication, the Destination ID is used as a link parameter. However with multi-hop communication
using the relay function, data is transmitted based on the route information set in the route register with the ‘@RT’
command or based on route information entered directly in the ‘@DT’ command. When using the relay function, use
data transmit command 2 or 3.
The MU-4 relay function does not perform retry between each station for data. The data from the source station is
transmitted at once through to the target station. When reliability is required for data transmission, use the ‘@DT’
command (/A, /B, %A, %B command options) that has an ACK response. It is possible to set a maximum of 10 relay
stations.
4.3.1 Transmission with the route register route information
The diagram below is an example of transmission based on route information set in the route register. Route
information is set only in the source station. In this case, use only the command option ‘/A’ or ‘%A’ for the ‘@DT’
command.
Source
station
Target
station
Relay
station
Relay
station
Relay
station
Relay
station
UI=0055
GI=01
EI=02
DI=Discretionary
RT=Discretionary
ACK
ACK
Packet Packet
UI=0055
GI=01
EI=03
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=04
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=0A
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=0B
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=01
DI=Discretionary
RT=02,03,04,0A,0B
Note: UI = User ID, GI = Group ID, EI = Equipment ID, DI = Destination ID, RT = Route information
Receive data ‘ABCDE’Transmit 5-byte data ‘ABCDE’
Data transmit command issued: @DT05ABCDE/A or @DT05ABCDE%A
Relay System Example 1 (Route information specified in the route register, with ACK response)
4.3.2 Transmission with the route information entered in the transmit command
The diagram below is an example of transmission with the route information entered directly in the command
option line of the ‘@DT’ command. Enter the route information in the ‘@DT’ command issued after ‘/A’ or ‘%A’. In
this case, the route information set in the route register is ignored.
Source
station
Target
station
Relay
station
Relay
station
Relay
station
Relay
station
UI=0055
GI=01
EI=02
DI=Discretionary
RT=Discretionary
ACK
ACK
Packet Packet
UI=0055
GI=01
EI=03
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=04
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=0A
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=0B
DI=Discretionary
RT=Discretionary
UI=0055
GI=01
EI=01
DI=Discretionary
RT=Discretionary
Note: UI = User ID, GI = Group ID, EI = Equipment ID, DI = Destination ID, RT = Route information
Receive data ‘ABCDE’Transmit 5-byte data ‘ABCDE’
Data transmit command issued: @DT05ABCDE/A02,03,04,0A,0B or @DT05ABCDE%A02,03,04,0A,0B
Relay System Example 2 (Route information entered directly in command, with ACK response)