Hello, My plan is to hopefully end up being able to manipulate waypoints through the mavlink protocol. I am trying to do this using the official Mavlink C library with asio for managing the serial/UART connection. I’m a complete noob when it comes to UART, mind you, but I feel like I got to a point, where I can’t really proceed. My reference is the uart example from the Mavlink repo.
I have a pixhawk2 flight controller that talks with my computer (macOS/Win64) through a pair of mRo 433 MHz SiK antennas. Currently my program sends nothing, I am just reading from the port.
BeingRX() initially calls when the port is opened from my computer:
void Serial::BeginRX()
{
// Owner of this Serial (port) is my "Bridge"
if(GetOwner() == nullptr)
{
throw;
}
Listen();
io_service.run();
}
Listen() looks for anything happening on the line:
void Serial::Listen()
{
// buffer size = 1 for STX
const size_t nbyte = 1;
// shared_ptr for moving into other object if needed in future
std::shared_ptr<std::array<uint8_t, nbyte>> buffer = std::make_shared<std::array<uint8_t, nbyte>>();
asio::async_read(port,
asio::buffer(*buffer, nbyte),
[this, buffer](const asio::error_code& ec, std::size_t bytes_transferred)
{
GetOwner()->ReadHandle_Listen(ec, bytes_transferred, buffer);
if (GetOwner()->bHasReceivedGoodRX())
{
// Parse data when this actually works
}
else
{
// Otherwise keep listening
Listen();
}
});
#ifdef DEBUG_COMMS
std::cout << "Listen() on " << GetPortID() << std::endl;
#endif
}
This is my Listen read handle, what happens when data is received:
void MavlinkBridge::ReadHandle_Listen(const asio::error_code& error_code, std::size_t bytes_transferred, std::shared_ptr<std::array<uint8_t, 1>> buffer)
{
#ifdef DEBUG_COMMS
MavlinkBridgeDebug::DebugMsg("Port received message");
#endif
if ( (error_code) || (bytes_transferred < 1) )
{
#ifdef DEBUG_COMMS
MavlinkBridgeDebug::DebugMsg(" Message received is faulty.");
#endif
return;
}
mavlink_message_t message;
mavlink_status_t* new_status = new mavlink_status_t;
uint8_t b_msg_has_been_received = false;
uint8_t b_message_is_good = false;
const unsigned int device_mavlink_version = mavlink_get_proto_version((*buffer)[0]);
b_message_is_good = mavlink_parse_char(MAVLINK_COMM_1, (*buffer)[0], &message, new_status);
if ( (last_status->packet_rx_drop_count != new_status->packet_rx_drop_count) ) // TODO: && debug )
{
std::cout << "Error reading: Packet loss." << std::endl;
}
if (b_message_is_good)
{
// Never happens
b_has_received_good_RX = true;
#ifdef DEBUG_COMMS
MavlinkBridgeDebug::DebugMsg(" Received good message.");
#endif
}
else
{
b_has_received_good_RX = false;
#ifdef DEBUG_COMMS
MavlinkBridgeDebug::DebugMsg(" Received bad message.");
#endif
}
#ifdef DEBUG_COMMS
std::cout << " " << (*buffer)[0] << std::endl;
#endif
}
I tried utilising the helper functions from the mavlink library but ultimately I didn’t understand how they should be utilised outside the example. It looks like the whole mavlink uart example got the whole message from reading one single char on the _read_port() function
Running the program I constantly get “bad” messsages. This is just a snippet of the above debug messages (With the “character” being from (*buffer)[0]), running on a Mac:
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
"
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
=
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
xfd
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
xe4
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
x8c
Listen() on /dev/tty.usbserial-DO01HWLH
[DEBUG] MavlinkBridge: Port received message
[DEBUG] MavlinkBridge: Received bad message.
xfd
I’m a bit lost, and I hope that perhaps someone could perhaps deduct what I am doing wrong.
I feel like I double checked the baud rate more than a few times now. The pixhawk baud rate is set to the default 1200, and so is the baud rate on the computer.
Regards