Foxtech RB20 User manual

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RB20
Signal Relay
user manual V2.1
2019.1

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Content
Disclaimer. .............................................................................................................. 3
Product Notes . ..................................................................................................... 3
Brief Introduction. ................................................................................................ 4
Product List. ........................................................................................................... 4
Using Instructions................................................................................................. 5
Ground Unit Diagram.......................................................................................... 5
Air Unit Diagram................................................................................................... 6
RB20 Indicators ..................................................................................................... 8
RB20 Connection Diagram. ............................................................................... 9
Parameter Configuration .................................................................................... 9
Out-of-Control Protection Setting
............................................................. 12
Firmware Upgrade............................................................................................. 12
FAQ. ....................................................................................................................... 14

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Thanks for purchasing the RB20 signal relay. Please use RB20 according to local
radio regulations. Please read this statement carefully before using it. Once used,
it is deemed to be an endorsement and acceptance of the entire contents of this
statement. Please strictly follow the instructions to install and use the product.
FOXTECH TRADE CO., LTD will not bear any legal responsibility for any consequences
and losses caused by improper use, installation, assembly and modification of
customers.
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1. Input voltage of RB20 ground and air unit is DC7.4 - 12V(lipo 2s - 3s)，please
strictly follow this parameter to power the module.
2. Be sure to install the antenna before powering up to avoid damage to the circuit.
3. Make sure that the antenna is free from obstructions in using process, and try to
keep away from large metal objects to avoid communication obstruction.
4. Do not disassemble or reassemble RB20 module, If you encounter problems that
cannot be solved during installation or use, please contact FOXTECH or your agent.
5. Keep the proper distance between the electronic devices during installation to
minimize electromagnetic interference between devices.
6. Make sure all connections are securely fastened and all parts are working properly
before use.
7. Please check the surrounding environment before use to ensure that there is no
interference from other 840MHZ-930MHZ equipment, otherwise the RB20 data
transmission may be seriously affected.

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RB20 Signal Relay is designed to work with radio controller to achieve the long range
requirements. The RB20 ground unit could be connected to PC through a TTL-USB cable,
to realize data transmission between PC and RB20 air unit, also could realize parameter
tuning. The max communicate range is 30km.
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Main Module
Ground Unit Air unit

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Accessories
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RB20 has 2 signal outputs: S-BUS and Serial port.if your remote controller or
receiver not support S-BUS, so you need to buy a PWMto S-BUS module.
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Poweer cable x2
usb cable
Data cable
（DC:7.4-12V) For grount unit parameter
tuning or serial connection
For air unit
parameter tuning

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RC Receiver

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Please check the connection status by following steps after the connection is
completed.(This step will have some differences because of different flight controls.)
1. Open the PC device manager and you can see that the ground unit is correctly
recognized, the driver is installed correctly, and there is no yellow exclamation
mark.
2. Open the FC ground station software,select the corresponding COM port, and connect to
the flight controller.The flight control is connected normally,indicating that the RB20 digital
transmission link is connected. If the connection fails, please check the following points.
1.The baud rate of the flight controller is same as the baud rate of RB20.
2.Ensure that the RB20 ground unit driver is installed successfully.
3.Use the RB20 parameter setting software to ensure that all parameter
settings for RB20 air and ground unit are consistent.
4.Ensure that RX of FC to TX RB20,TX of FC to RX RB20.
3. Open the rc setting interface of the ground station to check whether the remote
control data is normal. If the remote control data changes normally along with the
joystick. The remote control link is connected. If the remote control connection fails,
please check if the “-, +, signal” of the S-BUS is reversed.

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①S-BUS data indicator L1
L1 flashs means that the remote control has data transmission, and no flashing means that the remote control has
no data transmission.
②Configuration mode indicator L2
L2 steady light-in the configuration mode
③SET Button
Used to enter the configuration mode or set the runaway protection output value or upgrade firmware.
④Data transmission indicator
RXD light is on-receiver has data reception; TXD light is on-receiver has data transmission.
⑤Signal Strength
S1 S2 S3 - signal stregth indicator, all these three indicators are on- strongest signal quality; only S2󱾢S3 on-
middle-level signal quality; only S3 on-general signal quality.

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Power on the ground unit and air unit, if the light is illuminated as shown below, it
means the two modules are connected normally.
Air Unit
Ground Unit
Parameter Configuration
The parameters have been set at the factory and you should be able to use RB20 directly. In the following
situations, you may need to modify the RB20 parameters:
1.The flight control baud rate is inconsistent with the RB20 preset baud rate.
2.Multiple Rb20 occupy the same communication channel, causing communication blocking.
3.Have special communication bandwidth and communication power requirements.
Please follow the steps below to modify the parameters:
The parameter modification method of ground unit and air unit is basically the same, only the
connection cable is different.
1󱾢Press and hold the set button, then power up until the L2 light is on, release the button.
keeps on
keeps on
flashing
keeps on
keeps on
keeps on

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2、According to Pic.1 and Pic.2，connect ground unit to PC or connect air unit to
PC. Data cable for air unit: white cable connect to TX, black cable-GND, green
cable-RX.
Pic.1 Air unit connected to Configuration Software
Pic.2 Ground unit connected to Configuration Software

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3、 Use the matching assistant software, select the corresponding port and
click the connection to read the parameters, as shown in the figure below.
4、If you want to modify the parameters, just change the corresponding value
in the software, click on the Write, and then Confirm, as shown below.
5、After the modification is completed, press the Set button again or power up
again to exit the configuration mode.
Note: 1. Please ensure that the parameters of the ground unit and air unit are exactly the same, otherwise
the two modules cannot communicate.
2. Communication bandwidth and communication power directly affect communication quality and
communication distance󱾣If you don’t understand its meaning, please do not modify these two parameter
values.
3. After entering the configuration mode to complete the parameter configuration, be sure to exit the
configuration mode.
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RC Out-of-Control ProtectionSetting
If you need to set the using protection of the remote control, please follow the steps
below:
1. Write the runaway protection data
When the air end is properly connected to the ground end and there is remote control
data transmission, short press the set button of the air end (about 0.5S)， the value of the
current remote controller can be stored as an out-of-control protection value on the air
end, and will not be lost after power failure. Please use the FC ground station or servo to
test whether the runaway protection data is successfully written.
2. Trigger out-of-control protection value
When the air unit does not receive the S-BUS data from the ground unit for 3s the air end
will always output the previously written out-of-control protection value until the S-BUS
data from the ground end is received.
3. Turn off out-of-control protection
When the air end is properly connected to the ground end and there is remote control
data transmission, press and hold the Set button(≥3S) on the air unit to turn off the
out-of-control protection. Please use the FC ground station or servo to test whether the
out-of-control protection is successfully turned off.
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By default, the RB20 has no out-of-control protection value output.
While using RB20, please select the GCS Protection function, so when the aircraft does
not receive the S-BUS signal from the ground , the aircraft will automatically trigger and
return home.
Firmware Upgrade
1. Open Bootloader upgrade software

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2. connect to USB port or TTL port through a USB cable or data cable, Press and
hold the Set button and power on, then the L2 light is always on.Then press and hold
the Set button again until L1 and L2 are always on󾺭and the software displays the port
number at the same time, it indicates that the upgrade mode is entered.
3. Open the correct firmware you downloaded. If it is correct, will display
“firmware file identification is completed.”

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4. Click the Start button, until it prompts that the firmware writing operation
is completed, that means the upgrade is successful.
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1：receiver S-BUS has signal output󾺭but can not connect the serial port, or
transmission signal garbled.
Please check whether the baud rate of the serial port on the air unit and the
ground unit is the same; set the baud rate corresponding to the ground
station software.
2：Two or more devices have interference powered on at the same time.
The ID of each set must be different, and the channel should also be set
to a different value to avoid co-channel interference.