Texas Instruments CC900DB User manual

SWRU064
User Manual
CC900DB Demonstration Board
Rev. 2.0

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Table of contents
1 INTRODUCTION.....................................................................................................3
2 CC900DB DEMONSTRATION BOARD...............................................................4
2.1 BEFORE STARTING .................................................................................................4
2.2 DEMONSTRATOR OPERATION.................................................................................4
2.3 SYSTEM PARAMETERS ...........................................................................................5
2.4 CONFIGURATION REGISTER DATA ..........................................................................5
2.5 MICRO-CONTROLLER EEPROM MAPPING.............................................................7
2.6 TROUBLE-SHOOTING..............................................................................................8
3 DEMONSTRATION BOARD SOFTWARE DESCRIPTION.............................9
3.1 SLEEP MODE ..........................................................................................................9
3.2 ACTIVE MODE........................................................................................................ 9
3.3 DATA PACKET DESCRIPTION ..................................................................................9
3.4 DATA PACKET PROTOCOL .................................................................................... 10
3.5 DATA RECEPTION.................................................................................................11
3.6 DATA DECODER ALGORITHM ...............................................................................11
4 DEMONSTRATION BOARD HARDWARE DESCRIPTION .........................12
4.1 RF-SECTION......................................................................................................... 12
4.1.1 The loop filter...............................................................................................12
4.1.2 IF filter......................................................................................................... 12
4.1.3 The modulation input/output........................................................................12
4.1.4 LNA/PA matching ........................................................................................13
4.1.5 The Voltage Controlled Oscillator (VCO)...................................................13
4.1.6 The crystal oscillator ...................................................................................13
4.1.7 The antenna..................................................................................................13
4.2 CONTROLLER SECTION.........................................................................................14
4.2.1 RC oscillator ................................................................................................ 14
4.2.2 Micro-controller I/O .................................................................................... 14
4.2.3 In system programming................................................................................15
4.3 LAYOUT SKETCHES AND CIRCUIT DRAWINGS ....................................................... 16
4.4 CIRCUIT DIAGRAM ...............................................................................................18
4.5 BILL OF MATERIALS............................................................................................. 19
5 USING THE DEMONSTRATOR BOARD AS A PROTOTYPE MODULE...20

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1Introduction
The CC900 single chip RF transceiver includes many features and great flexibility,
which makes the chip suitable for a very large number of applications and system
requirements. The CC900DB Demonstration Board is designed to demonstrate how the
CC900 chip can be used in a simple two-way remote control. Full documentation is
provided for this module, including schematic, layout and micro-controller code, this
design will be a starting point and make it very easy for the user to evaluate transceiver
performance, and in a short time develop his own applications based on this reference
design.
The kit includes two CC900DB Demonstration Boards with a complete CC900
transceiver, micro-controller, integrated PCB antenna and battery. The Demonstration
Boards are pre-programmed to serve as a simple demonstrator. By pushing the “ON”
button, the device will be awakened. Both modules should be awaked before a
transmission takes place. A transmission is initiated by pushing the “TX” button. A
blinking sequence of approximately 2 seconds duration is then transmitted and shown on
the receivers LED. The same “message” is returned from the receiver to the initial
transmitter and shown on its LED as an “acknowledge”. The modules will enter sleep
mode after being left without operation for one minute.
Technical features:
-10 dBm RF power
Up to 30-meter range (depending on antenna orientation)
Small integrated shorted-stub antenna
<1uA power-down current in sleep mode
3.6V Lithium battery supply (~1000mAh)
SmartRF®Studio makes it possible to reconfigure the CC900DB system parameters by
inserting the Demonstration Board into the CC900EB Evaluation Board edge connector.
It is also possible to upgrade the Demonstration Board with new micro-controller
program code from SmartRF®Studio, see the SmartRF®Studio user manual for details.
The CC900DB is also designed to work together with the Atmel AVR micro-controller
STK500 development board, the in-system programmer ATAVRISP or similar. At the
rear side of the board there is a 10 pin connector foot-print which fits a 10-pin ISP cable.
This user manual describes how to use the Demonstration Board and how to use it to
develop your own applications. You will also find a detailed description of the circuit
board and the micro-controller code.
All available documentation can be downloaded from our web site. That includes:
CC900DB User Manual (this document)
CC900DB micro-controller code and configuration data
CC900 data sheet

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2CC900DB Demonstration Board
2.1 Before starting
The CC900DB runs on a 3.6V Lithium battery. If the battery is not mounted and
soldered to the board, insert the battery at the rear side of the board. Observe the LED. If
the LED is turned on continuously, push the “ON” button. For proper operation the LED
shall be pulsing with a period of approximately one second. If not, remove the battery
shortly and reconnect. The battery terminals should be soldered for proper operation.
Important: Be sure not to short-circuit the battery terminals during soldering or at any
point of use.
Before using the CC900DB: The use of radio transceivers is regulated by international
and national rules. Before transmitting a RF signal, please contact your local
telecommunication authorities to check if you are licensed to operate the transceiver.
2.2 Demonstrator operation
The CC900DB demonstrate a very simple two-way remote control system.
To “wake” the module from power-down mode, simply press the “ON” button for a
short time. The LED will then start blinking with a period of approximately 1 second.
This is the “heart-beat” that shows the module is operating. During the short time the
LED is lit, the module is in active receive mode, and listens for a data packet. If a data
packet is not found, it goes to a “rest” mode for approximately 1 second. Hence, the
module listens for a data packet every second. This polled receiver algorithm is
implemented in order to save battery power.
Both modules should be enabled before a successful transmission can take place. A
transmission is initiated by pushing the “TX” button. A data packet of approximately 1.5
second duration is then transmitted. The data packet consists of a long pre-amble and a
short data field. The preamble is longer that 1 second to ensure that the transmission
intercepts with the polled receiver.
The data packet transmitted consists of a blinking sequence of approximately 2 seconds
duration, and will be shown on the receiver’s LED if the data packet was received free
or errors. The same “message” with an acknowledgement flag is then returned from the
receiver to the initial transmitter. Again, the blinking sequence will be shown on the
LED as a receipt acknowledge.

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The modules will enter sleep mode after being left without operation for about one
minute. The CC900 and the micro-controller are then in power-down mode, ensuring
minimum power consumption.
The timing diagram below illustrates a packet transmission sequence when the
transmission is initiated from device number 2.
2.3 System parameters
The system parameters used to generate the configuration data for the CC900DB is
shown below. This is a printout from the SmartRF®Studio software.
System parameters:
X-tal frequency: 12.000000 MHz
X-tal accuracy: +/- 25 ppm
RF frequency: 868.300 MHz
IF stage: 200 kHz
Frequency separation: 40 kHz
Data rate: 1.2 kbps
Power amplifier class: Class AB
RF output power: -10 dBm
Mode: RX
Receiver mode: Optimum sensitivity
LOCK indicator: Continuous
VCO gain: 100
2.4 Configuration register data
Based on the system parameters referred above, the following configuration data is
generated. This is a printout from the SmartRF®Studio software.
DEVICE 1
DEVICE 2
Receiver polling
Devices are active for two
minutes until time-out
Initial
trans-
mission
Message
shown on
receiver LED
LED (ACK)
RX LED TX ACK
TX RX
Ack.
trans-
mission
Acknowledge
shown on
receiver LED
Sleep
mode

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RX mode:
Frame Addr/Data (hex)
A 006A
B 2B0B
C 4841
D 6033
E 8900
F BA00
G CB6C
H E072
TX mode:
Frame Addr/Data (hex)
A 086A
B 2B0B
C 4841
D 608F
E 8914
F BA00
G CB6C
H E072
PD osc. on mode:
Frame Addr/Data (hex)
A 186A
B 2B0B
C 4841
D 6033
E 8900
F BA00
G CB6C
H E072
PD osc. off mode:
Frame Addr/Data (hex)
A 186A
B 2B0B
C 4851
D 6033
E 8900
F BA00
G CB6C
H E042

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RX Precharge mode:
Frame AddrData (hex)
A 006A
B 2B0B
C 4841
D 6033
E 8900
F BA00
G CB6C
H E27A
In this application we have decided to use RX Precharge, RX, TX and PD osc. off
modes. Shown in bold in the listing above is the configuration data that is used, and
stored in the micro-controller EEPROM.
Note: The frame address is combined with the data to get a two-byte word consisting of
the 3 address bits (as MSBs) and the 13 data bits (as LSBs). The combined value is
shown in these listings.
2.5 Micro-controller EEPROM mapping
The CC900 configuration data are stored in the micro-controller EEPROM. The
following map shows the data location. To customise the module for a different
frequency or power level, the EEPROM data can be replaced by new values found using
the SmartRF®Studio software.
EEPROM
Address (hex)
Data (hex) Reference
00 086A TX frame A
02 2B0B TX frame B
04 4841 TX frame C
06 608F TX frame D
08 8914 TX frame E
0A BA00 TX frame F
0C CB6C TX frame G
0E E072 TX frame H
10 E072 RX frame H
12 006A RX PC frame A
14 2B0B RX PC frame B
16 4841 RX PC frame C
18 6033 RX PC frame D
1A 8900 RX PC frame E
1C BA00 RX PC frame F
1E CB6C RX PC frame G
20 E27A RX PC frame H
22 186A PD (osc. Off) frame A
24 4851 PD (osc. Off) frame C

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2.6 Trouble-shooting
If the module does not operate as described in this document, try the following.
Problem Possible solution
LED is continuously on Push the “ON” button once more. If this
does not work, reset the micro-controller
(see below).
LED does not start blinking after “ON” is
pressed
Check battery voltage. If less than 2.7 Volt,
replace battery. Only replace with a battery
of the same type.
If battery voltage is OK, reset the micro-
controller (see below).
Receiver does not receive packet from
closely located transmitter.
Use a Spectrum Analyser at 868.3 MHz to
check the module during transmission.
Connect the analyser to the external antenna
connector foot-print and measure the output
power and frequency using the “max hold”
function. The output power shall be
approximately –10 dBm with a peak at 868,3
MHz +/-10kHz.
Test the receiver the same way in transmit
mode.
The micro-controller can be reset by shorting the reset line to ground for a short
moment. The reset line is located at the edge connector pin 6. Ground is pin 1. The
orientation mark is between pin 2 and 3.

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3Demonstration Board software description
The demonstration board software is implemented in assembly and runs on the Atmel
AVR 8-bit micro-controller ATtiny12L.
The micro-controller handles the CC900 configuration, data encoding and decoding
using Manchester code, and implements a simple packet protocol.
A program listing with the assembly source code is available for reference and can be
used as a starting point for your own applications using the AVR series of controllers
from Atmel.
3.1 Sleep mode
When the CC900DB is left inactive for approximately one minute the CC900 is set to
power down mode, and the controller goes to “sleep”. The controller is awaked by an
interrupt signal at INT1 (pin 6).
In sleep mode the current consumption is less than 1 µA.
3.2 Active mode
In active mode the CC900 is used for receive polling. Once every second the CC900 is
set to RX mode, and the micro-controller starts searching for a preamble. The micro-
controller reads two data bits, if these are not Manchester coded 1’s, the CC900 is set to
power down mode again. The LED is lit during the pre-amble search and will appear as
a “heartbeat” signal.
In active mode the “TX” button input (PB2) is also monitored. If this line is pulled low
by the push button, the micro-controller will configure the CC900 to TX mode, and send
a predefined data packet at the DIO line (PB1), before returning to receiver polling.
3.3 Data packet description
The data packet consists of a pre-amble, a start-of-frame (SOF), and a data field.
The pre-amble is a train of ‘1’s. The train is longer than 1 second in order to ensure that
it intercept with a polled receiver.
The SOF consists of two consecutive ‘0’s. The SOF marks the end of the preamble, and
the start of the actual data.
The data field consists of ID (identification), TYPE (packet type) and DATA (user data,
3 bytes). No FEC (forward error correction) or CRC (cyclic redundancy check) is used
in order to keep it as simple as possible.

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The ID is intended to be used for unique identification of different modules. However,
this is not exploited in this software revision. All modules are addressed using the public
address (0x00).
The TYPE is used to separate between an original message (0x00) and an acknowledge
(0x01).
The 3 DATA bytes are used to code the blinking sequence. Every bit represents a 0.1
seconds period approximately.
No end of packet is implemented.
The data packet is shown in the figure below.
Preamble SOF ID TYPE DATA1 DATA2 DATA3
The figure below shows the symbol coding and an example of a packet with the pre-
amble, data and SOF timing.
Preamble for >1 second SOF
Data field:
ID, TYPE, DATA1,2,3
Preamble (synch symbol):
SOF, start of frame:
Data symbols (Manchester code): 1= 0=
3.4 Data transmission protocol
The data transmission protocol is very simple, only using packet acknowledgement.
When a data package is received without errors, the packet type is checked. If it is an
original message, it is shown on the LED, and an acknowledgement is sent as a reply.
However, if it is an acknowledgement packet that is received, the message is only shown
on the LED without any reply.

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3.5 Data reception
The data reception algorithm is as follows:
1. Enter RX precharge mode, wait
2. Enter RX mode
3. The receiver shall receive synchronisation pattern (pre-amble) for some periods
before it is allowed to detect SOF
4. Wait for SOF
5. Receive and decode data
6. Display data on LED
3.6 Data decoder algorithm
The decoder algorithm implemented is based on oversampling. Each bit is sampled 8
times, and the data decision is based on a majority vote. The use of oversampling makes
the data decision more immune to noise and duty cycle variations than a data decision
algorithm based entirely on detecting edges.
The oversampling algorithm synchronises on the preamble, and thereafter continues to
synchronise itself by detecting edges.
For more information on oversampling, see application note AN008 : Oversampling and
data decision.

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4Demonstration Board hardware description
4.1 RF-section
The RF section consists of a CC900 chip with a few external components. The different
parts of the circuit are explained below.
4.1.1 The loop filter
The PLL loop filter contains the components C121-C123 and R121-R123. The
SmartRF®Studio software program has been used to calculate the component values.
Using the calculated component values for the loop filter gives an optimum loop
bandwidth for the selected system parameters.
The transmitted frequency is FSK modulated, which means that the bits ‘0’ and ‘1’ is
coded by jumping between two different frequencies. The loop filter bandwidth is
optimised according to the frequency separation (difference between the two
frequencies) and the data rate (the speed we jump between these two frequencies).
4.1.2 IF filter
The Demonstration Board uses the internal 200kHz IF filter. The 200kHz IF filter has a
larger bandwidth than the 60 kHz IF filter, and therefor allows us to use a less accurate,
and hence less expensive crystal. The sensitivity is slightly less than for the 60 kHz IF,
but is considered adequate in this application.
4.1.3 The modulation input/output
The modulation input/output (DIO) is connected to a micro-controller I/O pin. The data
to be sent is Manchester encoded (also known as bi-phase-level coding) by the micro-
controller. The Manchester code ensures that the signal has no DC component, which is
necessary for the FSK demodulator to work in an optimal way. The Manchester code is
based on transitions; a “0” is encoded as a low-to-high transition, a “1” is encoded as a
high-to-low transition. This is illustrated in the figure below.
Time
TX
data
10110001101

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4.1.4 LNA/PA matching
The input/output antenna matching network is optimised for 869.3 MHz operation. The
component values were calculated in the SmartRF®Studio software program, and
consists of C51, L51 and L61. To compensate for layout parasitics the component values
were tuned to optimise for 50 Ohm input impedance in receive mode, and maximum
output power in transmit mode.
4.1.5 The Voltage Controlled Oscillator (VCO)
The VCO tank is optimised for the 868MHz band, covering approximately 840 –
904MHz. The tank contains the components C91, C92, C93, L91 and the variable
capacitance D2.
4.1.6 The crystal oscillator
The crystal oscillator frequency is 12.000 MHz set by X1. We have chosen a +/-10 ppm
crystal for this application. The crystal is specified as 10/10/10/12, which means that has
a +/-10ppm initial tolerance, and will drift less than +/-10ppm over a temperature range
of –10 to 70°C. SmartRF®Studio specifies a total crystal accuracy of 0/-25ppm for the
parameters used here. This means that we have 10+10=20ppm of worst case deviation
from the specified frequency over the entire temperature range, leaving 5ppm for ageing
and safety margin. A crystal of this type will drift with age less than +/-3ppm/year (often
specified for +/-5ppm the first year), if long product life is anticipated, a higher accuracy
crystal, or one with low ageing, should be used.
The loading capacitors, C151 and C161, together with the input capacitance and
paracitics makes up the total 12pF load capacitance the crystal is designed for.
4.1.7 The antenna
This antenna is an example of a PCB integrated antenna. Several antenna configurations
were evaluated, and the λ/4 PCB stub was found to be the best solution for this
application. The stub is approximately one-quarter wavelength (λ/4 = 8.63 cm at
869MHz), and on therefor just need a 0 ohm at L8.
In general, small electrical antennas are not very efficient. Electrical stub antennas
should be designed as long as possible, up to one-quarter wavelength. They should be
kept away from the ground plane and other surrounding metallic bodies. For hand-held
remote controls, the antenna should not be in close contact with the hand. If this can not
be avoided, a magnet loop antenna could be used. The loop is less sensitive to nearby
objects, but suffers of very low efficiency due to very low radiation resistance. The stub
antenna implemented at the Demonstrator PCB showed better efficiency than a loop of
similar size, even when operated hand-held. For maximum efficiency, the antenna
should be pointed straight up.

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4.2 Controller section
The controller section consists of an Atmel AVR ATtiny12L micro-controller with a few
external components.
4.2.1 RC oscillator
The internal RC oscillator is used as reference time base. The oscillator frequency is
relatively independent of temperature and operating voltage. Its nominal frequency is 1.2
MHz, varying less than +/- 5% over the application temperature and supply voltage
range. A calibration feature utilising a calibration word programmed into the micro-
controller at the factory ensures that the oscillator frequency is equal from unit to unit.
4.2.2 Micro-controller I/O
As the controller is packed in an 8-pin package, it has room for only 5 external I/O lines.
These are combined serving several functions in different operating modes.
The micro-controller has only one interrupt input, PB1/INT0. This input is shared
between the “ON” button and the DIO signal to CC900. In sleep mode the controller
will be awaked by an interrupt when this line is forced low by the push button. In
receive mode the interrupt is used for data decoding. During transmit the pin is
configured as an output.
The table below shows the function of all I/O pins in the various modes.
Signal/pin Program
loading
Demonstrator Comment
PB0, pin 5 MOSI LED
PB1/INT0,
pin 6
MISO DIO
“ON” in sleep mode
Interrupt input
PB2, pin 7 SCK CLOCK
“TX”
PB3, pin 2 STROBE
PB4, pin 3 PDATA

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4.2.3 In system programming
By connecting the CC900DB to the CC900 evaluation board, SmartRF®Studio can
reprogram the micro-controller while in the circuit. Both the program code memory
(flash) and the EEPROM can be reprogrammed. (an ATMEL AVR STK500
development board or an ATAVRISP in-circuit programmer can also be used).
The programming interface uses 4 signal lines. These four lines can be accessed at both
the 10-pin connector footprint at the rear of the board, and at the edge contact. Pin-out is
listed in the table below.
Signal/pin AVR
programming
socket, pin
Edge connector,
pin
MOSI 1 4
MISO 9 5
SCK 7 3
RESET 5 6
GROUND 4,6,8,10 1,2

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4.3 Layout sketches
Drawing not to scale.

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4.4 Circuit diagram

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4.5 Bill of materials
CC900DB
Reference Description Value Part
B1 Battery 3.6V LS14250 3PF, Lithium Thionyl Cloride, SAFT
C1 Capacitor, tantal 3.3µF C_3U3_TAN_B
C2 Capacitor 0603 33nF C_33N_0603_X7R_K_25
C3 Capacitor 0603 220pF C_220P_0603_NP0_G_50
C10 Capacitor 0603 1nF C_1N0_0603_X7R_K_50
C11 Capacitor 0603 33nF C_33N_0603_X7R_K_25
C12 Capacitor 1206 1nF C_1N0_0603_X7R_K_50
C24 Capacitor 0603 220pF C_220P_0603_NP0_G_50
C25 Capacitor 0603 12pF C_12P_0603_NP0_G_50
C51 Capacitor 0603 220pF C_220P_0603_NP0_G_50
C52 Capacitor 0603 8p2F C_8P2_0603_NP0_C_50
C53 Capacitor 0603 8p2F C_8P2_0603_NP0_C_50
C91 Capacitor 0603 3.9pF C_3P9_0603_NP0_C_50
C92 Capacitor 0603 3.9pF C_3P9_0603_NP0_C_50
C93 Capacitor 0603 1pF C_1P0_0603_NP0_C_50
C121 Capacitor 0603 680pF C_680P_0603_NP0_J_50
C122 Capacitor 0603 33pF C_33P_0603_NP0_J_50
C123 Capacitor 0603 6.8pF C_6P8_0603_NP0_C_50
C151 Capacitor 0603 15pF C_15P_0603_NP0_G_50
C161 Capacitor 0603 15pF C_15P_0603_NP0_G_50
C210 Capacitor 0603 1nF C_1N0_0603_X7R_K_50
C211 Capacitor 0603 33nF C_33N_0603_X7R_K_25
D1 LED Red CL150, Citizen
D2 Varactor diode BBY53-03W
H1 Shield can SHIELD_CAN_400X400
L7 Capacitor 0805 N.A
L8 Resistor 0805 0 ΩR_0R_0805
L51 Inductor 0805 8.2nH L_8N2_0805_J
L52 Inductor 0805 3.3nH L_3N3_0805_D
L61 Inductor 0805 100nH L_100N_0805_J
L91 Inductor 0805 3.3nH L_3N3_0805_D
L210 EMI filter bead BLM11A102S, Murata
R1 Resistor 0603 10kΩR_10K_0603_G
R2 Resistor 0603 1kΩR_1K0_0603_J
R3 Resistor 0603 1kΩR_1K0_0603_J
R4 Resistor 0603 0ΩR_0R_0603
R5 Resistor 0603 1kΩR_1K0_0603_J
R6 Resistor 0603 470ΩR_470_0603_J
R7 Resistor 0603 10kΩR_10K_0603_G
R121 Resistor 0603 47kΩR_47K_0603_G
R122 Resistor 0603 220kΩR_220K_0603_J
R123 Resistor 0603 22kΩR_22K_0603_G
S1 Push button PUSH BUTTON
S2 Push button PUSH BUTTON
U1 Single chip transceiver CC900
U2 Micro-controller ATtiny12L-4SC
X1 Crystal, HC-49-SMD X_12.000000 MHz, 10/10/10 tol., 12pF load

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5Using the Demonstrator Board as a prototype module
The purpose of the Demonstrator Board is to show a simple transceiver module with
battery supply and integrated PCB antenna. The demonstrator can be used “as is” for
simple range and coverage measurements. But keep in mind that this module use only 0
dBm and a small rather ineffective antenna. The range can be extended substantially
using more power and a better antenna.
The Demonstrator Board can also be used as a prototype module when developing your
own applications. You may:
•Reprogram the EEPROM configuration data for your own system parameters. The
SmartRF® Studio generates the configuration data values. See section 2.5 for
EEPROM memory map.
•Rewrite the microcontroller code to use the edge connector to interface your host
system
•Insert a standard 2.54 mm pitch contact to interface a motherboard at the edge
connector.
•Remove L8, and mount a coax connector at the antenna output. Thus an external
antenna could be used. The antenna should be matched to 50 Ohm