ARM/DISARM command to PX4

MAVLink
1

Morning. I’m a beginner in this. I’m trying to send an arm/disarm command from an Arduino to PX4, I wanna know where’s the mistake in my code.

I have a command_long handler function and a send_command function.

void handle_command_long_packet(mavlink_message_t message){
  mavlink_command_long_t cmd;
  //mavlink_msg_command_long_decode(const mavlink_message_t *msg, mavlink_command_long_t *command_long)
  mavlink_msg_command_long_decode(&message, &cmd);


  switch(cmd.command){
    case MAV_CMD_COMPONENT_ARM_DISARM:{
      Serial1.print("ARM/DISARM COMMAND");
      send_long_command(MAV_CMD_COMPONENT_ARM_DISARM, 0, 1, 0, 0, 0, 0, 0, 0);
      send_ack_message(MAV_UAV_ID, MAV_UAV_COMP_ID, MAV_CMD_COMPONENT_ARM_DISARM, MAV_RESULT_ACCEPTED, 0, 0, MAV_GCS_ID, MAV_GCS_COMP_ID);
    }
  }
}


void send_long_command(uint16_t command, uint8_t confirmation, float param1, float param2, float param3, float param4, float param5, float param6, float param7){
  mavlink_message_t msg;
  uint16_t len;

  mavlink_msg_command_long_pack(MAV_GCS_ID, MAV_GCS_COMP_ID,&msg, MAV_UAV_ID, MAV_UAV_COMP_ID, command, confirmation, param1, param2,  param3,  param4, param5, param6,  param7);
  len = mavlink_msg_to_send_buffer(buffer, &msg);

  Serial1.write(buffer,len);
}

I’d like to know if you could provide me a source besides this article: Mavlink and Arduino step by step

2

If you’re a beginner, then you have set yourself a tricky challenge. MAVLink can be a bit challenging to get right.

I would do any of these:

  • use a higher level library (e.g. MAVSDK) on a Raspberry Pi instead
  • get inspiration from how things are done within other implementation (e.g. arming in MAVSDK or this MAVLink example.
  • Use an LLM to help you with this. It should do an ok job for that sort of thing as you’re not the first one trying that.
3

What library are You using?
First check that PX4 port is configured and baud rate matches with your Arduino.