ModalAI Forum

@Eric-Katzfey Hey, we already have this board on https://www.modalai.com/collections/expansion-board/products/m0078 - would that work?

(and the PWM breakout board https://www.modalai.com/products/flight-core-pwm-output-cable-and-break-out-board)

@Eric-Katzfey Hi Eric, thanks for pointing this out. How would you go about establishing a serial communication with a Teensy or other microcontroller then?

Hi, I'd like to communicate with a teensy from a Voxl2 through the serial channel on J18. Can you help me set this up?

I tried UART first and then the I2C but I haven't figured this out. Here's my code

import smbus

# Open the I2C bus
bus = smbus.SMBus(0)  # Use /dev/i2c-0

# I2C device address
address = 0x988000  # Replace with the actual I2C device address

# Read lines of data from the I2C device
while True:
    received_data = ""
    while True:
        byte = bus.read_byte(address)
        if byte == ord('\n'):  # Check for newline character
            break
        received_data += chr(byte)

    # Process the received data
    print("Received line:", received_data)

# Close the I2C bus
bus.close()

and the one I want to use on the teensy

#include <Wire.h>

#define I2C_ADDRESS 0x42  // Replace with the I2C device address

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(115200); // Set baud rate for serial monitor
}

void loop() {
  Wire.beginTransmission(I2C_ADDRESS);  // Begin transmission to the I2C device
  Wire.write("Hello, World!");  // Send the message
  Wire.endTransmission();  // End transmission

  Serial.println("Message sent!");

  delay(1000); // Wait for 1 second before sending the next message
}

This is my first attempt at dealing with I2C so extra comments are welcome as well. Would still be easier if I could use these pins for UART so tell me if that's an option.

Thanks!

@Eric-Katzfey Yeah ok I think I got it. So just execute the above dpkg install. Would be cool if it checked for updates itself every once in a while

@Eric-Katzfey Is this just a command to execute on the voxl, px4 will be updated and all else remain equal - custom configs and all?

Thanks

@Vinny Hi, is there any update on this CAN support through FlightCore V2?

We're seriously considering the option instead of a PWM through the I/O board to control our motors. Unfortunately, I can't seem to find any code that would do this from the PX4 pilot - other than that the connector exists. How is this supported by the board interfaces? How would I go about sending commands to that bus?

Let me know if you need more info.
Best

Any tips on how to control this from ROS for offboard mode?

Yes, thanks. Although incomplete
Need to configure quad_x_io.main.mix (find / -name "filename") with the code below where X is the channel defined in the 2nd link below (AUX1 5 or AUX2 6)

# Hexacopter X airframe config
R: 6x ...
# For each AUX channel
M: 1
S: 3 X ...

Writing this from home, sorry for '...' but simply copy the config to quad_x.main.mix to quad_x_io.main.mix, both these files are loaded on boot and if the io board is connected it overrides the former

AUX1 will be on pin7 and AUX2 on pin8.

1. https://docs.px4.io/v1.12/en/concept/mixing.html
2. https://docs.modalai.com/voxl2-io-user-guide/#supported-mixers-and-airframe-setup

Or properly rename the file and change the name being loaded in the px4 startup script but I didn't do that to avoid issues in case it's used by something else too...

def gpio_init(pin):
    with open("/sys/class/gpio/export", "w") as config:
        config.write(str(pin).encode())
    return

def gpio_exit(pin):
    with open("/sys/class/gpio/unexport", "w") as config:
        config.write(str(pin).encode())
    return

def gpio_set_mode(pin, direction):
    with open("/sys/class/gpio/gpio{}/direction".format(pin), "w") as mode:
        mode.write(str(direction).encode())
    return

def gpio_set_value(pin, value):     
    with open("/sys/class/gpio/gpio{}/value".format(pin), "w") as gpio:
        gpio.write(str(value).encode())
    return
     

Hi all,

How should I go about controlling the PWM channel 7 or 8 (hexacopter airframe) from VOXL2 code and/or remote control? I can't find where the AUX channels are mapped

Thx

@tom said in VOXL2 unused/repurposed GPIO:

VOXL 2 Linux User Guide

ModalAI technical documentation for VOXL and VOXL 2 Companion Computers for PX4 and ArduPilot Obstacle Avoidance and GPS-denied navigation, assembled in the USA

ModalAI Technical Docs (docs.modalai.com)

Indeed, thanks for the fast reply. I also just ran into the bind.c here https://forum.modalai.com/topic/1466/voxl2-gpio-and-serial-interfaces/3 and turns out I didn't account for the chip offset. How do I figure out which one to use? In this case it was 1100. This should now be a permanent setting right?

To modify those from code I could copy the _gpio_control function above and use it in a ros package, right? I am looking for a clean way to do this. Please tell me if there's a better way to directly toggle based on radio signal.

Also, I can't find any python code examples, are there any?

Hey, trying to do something very similar myself.

Can't seem to toggle pin 46 on the VOXL2 J10. Following docs.modalai.com/voxl-gpio-io I run into the following:

voxl2:~$ echo 46 > /sys/class/gpio/export
-bash: echo write error: Invalid argument

Eventually, I'd like this to match the state of a radio remote control switch to kill another board's power supply. Maybe through ROS
but preferably not. Can you guide me through it please?