Hi, we’ve been working on communication between raspberry pi and the pixracer, anyone has a working configuration? We’ve been hitting on all the walls on this, haven’t got them to communicate at all. Here’re the things we’ve tried:
used firmware 1.8.1/1.8.2/1.9.0/1.6.3
SYS_companion set to 921600 (for 1.8.1/1.8.2/1.6.3)
for 1.9.0:
MAV_2_config=telem2
MAV_2_mode=onboard
MAV_2_rate=921600
MAV_2_forward=true
also tried SER_TEL2_BAUD to 921600
they always fail at after executing px4.launch and no data streaming. we are running out of walls to crash into. Anyone has ideas? Thanks in advance.
We’re successfully using the PixRacer and an Up Core, however for serial on the companion side we are using an FTDI chip (this one).
We have:
MAV_1_CONFIG=TELEM 2
MAV_1_FORWARD=Disabled
MAV_1_MODE=Onboard
MAV_1_RATE=80000 B/s
SER_TEL2_BAUD=921600 8N1
Hope this helps!
I have this working but i cannot claim the knowledge. I purchased from gennady…
Hi! I am using the same FTDI chip and the Pixracer as well as the same MAV settings. Have you done any modifications on the 6-pin cable? When I just connect it it doesn’t work. Using screen /dev/ttyUSB0 921600 8N1 for example, there is absolutely nothing on the port.
Hello!
What about using the CAN (and UAVCAN) to dialog to the companion computer instead of UART port?
Hi,
Same situation on my test. Did you resolve this issue? I didnt get the heartbeat response. Anyone has solution?
Hi,
it has been a while since I solved it. You need to cut and solder the TX/RX cables. By default, they are TX->TX and RX->RX, because it’s just a standard cable which is used differently for other ports. In our case, you need to connect TX->RX/RX->TX, that is, cross them.
For the Mavlink settings, apart from the default, I’m using this now:
TELEM 1 - Radio telemetry
MAV_0_CONFIG 101 TELEM 1
MAV_0_MODE 0 NORMAL
MAV_0_RATE 1200 Default rate for radio telemetry (not 57600)
TELEM 2 - Companion computer communication
MAV_1_CONFIG 102 TELEM 2
MAV_1 FORWARD 1
MAV_1_MODE 1 CUSTOM
MAV_1_RATE 1500000 Rate for companion computer communication
Where I chose CUSTOM to only stream the topics I need. The topics to stream can be set here: https://github.com/PX4/Firmware/blob/5f1121c216c254a6bb7e752999ab1b9d2a0833d9/src/modules/mavlink/mavlink_main.cpp#L1743
Don’t get confused by the fact that the MAVROS node always creates ALL topics (rostopic list). But it depends on your MAV_ _MODE setting, to which topics it actually publishes messages.
Thanks for quick response. 
I tried your solution but i still didnt get heartbeat response. Which ftdi cable do you use?
I use this FTDI adapter: https://store.mrobotics.io/USB-FTDI-Serial-to-JST-GH-p/mro-ftdi-jstgh01-mr.htm
I’ve also cut the power cable, as mentioned here: http://dev.px4.io/v1.9.0/en/companion_computer/pixhawk_companion.html#hardware-setup
How is your pixhawk powered/connected? Is it running (LEDs)? How do you try to connect?
I connected pixhawk via usb port and it is running. I check the link via qgc.
Do I understand correctly that you power the pixhawk from an external battery? Your FTDI adapter is connected between Pixhawk TELEM… and your computer USB port?
I’m not sure wether QGC would connect automatically via FTDI. Go to QGC settings>General: Uncheck AutoConnect>Pixhawk/SiK Radio/…
Then Comm Links>Add: Serial, SerialPort -> Select the device name of your FTDI adapter, Baud Rate 921600.
Then click the connect button on the same screen.
