[TUTORIAL] Connecting Vicharak Axon with Pixhawk as a companion computer

vigu · April 30, 2025, 6:55am

This tutorial assumes you have already flashed ArduPilot on your Pixhawk and finished the needed calibrations

Requirements

Pixhawk (for this tutorial, 2.4.8 was used, the same process should follow for other versions)
Vicharak Axon
3x Female-female jumper cables (Optional)
6-pin female connector (to connect to TELEM1) (Optional)
Micro-USB cable (To connect Vicharak Axon with Pixhawk)

Procedure (To only connect TELEM2)

Note about TELEM2

Note that this method WILL NOT give commands/instruct Pixhawk. This port is only meant for receiving parameters/readings from Pixhawk during the flight.

0. Set the following parameters in your ArduPilot Parameters file

This can be done using MissionPlanner or QGroundControl.

Change the parameters as follows

SERIAL2_PROTOCOL = 2 
SERIAL2_BAUD = 921

Restart the device normally to ensure the parameters are written.

1. Ensure UART is enabled by checking in `vicharak-config`

Search for vicharak-config in the search bar or run sudo vicharak-config in the terminal

Head over to Overlays -> Press "Yes" -> Select "Enable UART1 on 30 Pin GPIO Header Axon v0.3" -> Press "Ok" on the bottom

Note on UART ports

You are free choose whatever UART port you think is comfortable for you and modify your connections accordingly

You will now be prompted to reboot in order applying the settings.

Verify if the UART port has been enabled by running ls /dev/ and checking if ttyS1 exists

Note for using other UART ports

Your serial device may vary depending on the UART ports enabled in vicharak-config, the device must be /dev/ttySX where X is the UART port number enabled

2. Make the needed connections

These are the pinouts of the TELEM2 port on Pixhawk

Pin	Signal	Voltage
1 (Red)	VCC	+5V
2 (Black)	UART5_TX (out)	+3.3V
3 (Black)	UART5_RX (in)	+3.3V
4 (Black)	UART5_CTS (in)	+3.3V
5 (Black)	UART5_RTS (out)	+3.3V
6 (Black)	GND	GND

However, we will not be needing pins 1, 4 and 5.

Connect pins (from Pixhawk) 2, 3 and 6 to Axon’s GPIO pins 10, 12 and 8 respectively, or follow the table as follows

Pins (Pixhawk)	Pins (Axon)
UART5_TX (2)	UART1_RX_M0 (10)
UART5_RX (3)	UART1_TX_M0 (12)
GND (6)	GND (8)

You can also find the respective pins on bottom of Axon in case you are not sure about the connections you have made

3. Give access to users to access the port

By default, only root is allowed to access the serial devices. Generally, the policy to allow reading serial devices is only given to dialup group in linux

Try $ sudo usermod -aG dialup $USER to add yourself to the dialup group. Logout and log back in to see the effects

In case you don’t wish to screw around with the groups and want to give all users the access to only the specific serial device

$ sudo chmod a+rw /dev/ttyS1

Note for using other UART ports

Replace 1 above with another UART port that you may have enabled

4. Create a python virtual environment and install needed dependencies

Assuming you are using Ardupilot, you can interact with Pixhawk in a variety of different ways. The most commonly used library for interfacing with Ardupilot is DroneKit.

DroneKit, however, tends to work best python3.9.

To get python3.9, add the deadsnakes PPA, which allows you to install and use older versions of Python which may no longer be in Ubuntu’s repositories

$ sudo apt install software-properties-common
$ sudo add-apt-repository ppa:deadsnakes/ppa
$ sudo apt install python3.9 python-venv3.9

Create a new Python environment (preferably in a folder of your choice where you will be managing rest of your scripts)

$ python3.9 -m venv hello_dronekit
$ source ./hello_dronekit/bin/activate
$ pip install pyserial dronekit MAVProxy mavsdk

This should suffice with almost any possible interaction you may need with Pixhawk.

You are encouraged to read through each library’s documentation to make the best possible use out of them

5. Test your setup

If you have followed all the instructions thus far, there should be nearly no issues in this step. Simply run (after activating the virtual environment)

$ mavproxy.py --master=/dev/ttyS1 --baud=926100

If all goes well, you should see a screen similar to this (ignore the sudo)

AttributeError: module 'collections' has no attribute 'MutableMapping'

Python regularly makes changes to its dependency structure, which may cause issues like these to show up. To fix this, make the following changes:

Line	From	To
1	import collections	from collections.abc import MutableMapping
2689	class Parameters(collections.MutableMapping, HasObservers)	class Parameters(MutableMapping, HasObservers)

Alternative Procedure (Using MicroUSB)

If the method above seemed tricky to get working, there is fortunately an alternative (and much easier) method to get going

In contrast to TELEM2, using MicroUSB allows 2-way communication between Axon and Pixhawk - meaning you can send commands and make work with complex scripts

1. Give access to users to access the port

By default, only root is allowed to access the serial devices. Generally, the policy to allow reading serial devices is only given to dialup group in linux

Try $ sudo usermod -aG dialup $USER to add yourself to the dialup group. Logout and log back in to see the effects

In case you don’t wish to screw around with the groups and want to give all users the access to only the specific serial device

$ sudo chmod a+rw /dev/ttyACMX

Depending on which USB port is used, X can be 0 or 2 (rarely even 1). You can verify the value of X by verifying the output of $ ls /dev/

The physical connection is very straightforward as shown in the image

2. Create a python virtual environment and install needed dependencies