windows "COM22" linux "/dev/ttyACM0" power usb port linux "/dev/ttyUSB0" ftdi usb plug to telem1 or telem2 port
added windows support changed pthreads to c++11 threads added mission several different mission commands able to set and alter autonmous waypoints added messages to help support this behavior
local ned init check removed because ardupilot fails to send local ned on start up. Arduplane does not support guided mode atm. Enabling offboard control will return unkown or unsupported command.
C-UART Interface Example
This is a simple MAVLink to UART interface example for *nix systems that can allow communication between Pixhawk and an offboard computer.
This example will recieve one MAVlink message and send one MAVlink message.
Building
$ cd c_uart_interface_example/ $ make Hardware Setup
Connect the USB programming cable to your Pixhawk.
If you want to be able to interact with this example in Pixhawk's NuttX shell, you'll need a Telemetry Radio or an FTDI developer's cable. See the Exploration section below for more detail.
Note: Serial 5's receive pin is occupied by a second NuttX shell and can't be used to receive data without reconfiguration.
Also Note: Using a UART (serial) connection should be preferred over using the USB port for flying systems. The reason being that the driver for the USB port is much more complicated, so the UART is a much more trusted port for flight-critical functions. To learn how this works though the USB port will be fine and instructive.
Execution
Login to Pixhawk's shell screen /dev/ttyACM0 57600 8N1 You have to pick a port name, if the above example doesn't work, try searching for it with
$ ls /dev/ttyACM* $ ls /dev/ttyUSB* Alternatively, plug in Pixhawk USB cable again and issue the command:
$ dmesg The device described at the bottom of dmesg's output will be the port on which the Pixhawk is mounted.
The Pixhawk USB port will show up on a ttyACM*, an FTDI cable will show up on a ttyUSB*.
Start a mavlink session on Pixhawk's USB port nsh> mavlink start -d /dev/ttyACM0 Pixhawk will start dumping machine data to the shell.
Exit screen with the key sequence: Ctrl+A , K, Y
Run the Example Executable $ cd c_uart_interface_example/ $ ./mavlink_control -d /dev/ttyACM0 To stop the program, use the key sequence Ctrl-C.
Here's an example output:
OPEN PORT Connected to /dev/ttyUSB0 with 57600 baud, 8 data bits, no parity, 1 stop bit (8N1)
START READ THREAD
CHECK FOR HEARTBEAT Found
GOT VEHICLE SYSTEM ID: 1 GOT AUTOPILOT COMPONENT ID: 50
INITIAL POSITION XYZ = [ 8.2935 , -1.1447 , -0.7609 ] INITIAL POSITION YAW = 2.1539
START WRITE THREAD
ENABLE OFFBOARD MODE
SEND OFFBOARD COMMANDS POSITION SETPOINT XYZ = [ 3.2935 , -6.1447 , -0.7609 ] POSITION SETPOINT YAW = 2.1539 0 CURRENT POSITION XYZ = [ 8.2935 , -1.1447 , -0.7609 ] 1 CURRENT POSITION XYZ = [ 8.2935 , -1.1447 , -0.7609 ] 2 CURRENT POSITION XYZ = [ 8.2524 , -1.1444 , -0.7667 ] 3 CURRENT POSITION XYZ = [ 8.2205 , -1.1431 , -0.7747 ] 4 CURRENT POSITION XYZ = [ 8.1920 , -1.1421 , -0.7737 ] 5 CURRENT POSITION XYZ = [ 8.1920 , -1.1421 , -0.7737 ] 6 CURRENT POSITION XYZ = [ 8.1539 , -1.1414 , -0.7847 ] 7 CURRENT POSITION XYZ = [ 8.1522 , -1.1417 , -0.7820 ]
DISABLE OFFBOARD MODE
READ SOME MESSAGES Got message LOCAL_POSITION_NED (spec: https://pixhawk.ethz.ch/mavlink/#LOCAL_POSITION_NED) pos (NED): 8.152975 -1.141093 -0.784075 (m) Got message HIGHRES_IMU (spec: https://pixhawk.ethz.ch/mavlink/#HIGHRES_IMU) ap time: 3611390110 acc (NED): 0.005503 0.044659 -9.740363 (m/s^2) gyro (NED): -0.003064 0.003857 0.000005 (rad/s) mag (NED): -0.117767 -0.335362 -0.253204 (Ga) baro: 1020.519958 (mBar) altitude: -60.341393 (m) temperature: 46.779999 C
CLOSE THREADS
CLOSE PORT Exploration
There are a few things to explore past this example.
First you can connect via a Telemetry Radio on Telem 1 or 2, or via an FTDI on Telem 2 or Serial 4 (https://pixhawk.org/dev/wiring). Note: Serial 5's receive pin is occupied by a second NuttX shell and can't be used to receive data without reconfiguration.
With this you'll be able to start a second port for communcation, and leave the USB port available for viewing prints in the NuttX shell.
For steps 2 and 3 from the above tutorial, you'll use a different port. On the off-board computer side, the port might now be /dev/ttyUSB0. On the Pixhawk side, here the port mappings are in the table below.
PX4 UART NuttX UART Telem 1 /dev/ttyS1 Telem 2 /dev/ttyS2 Serial 4 /dev/ttyS6 Now add a print statement in the Pixhawk Firmware to see received messages. Build and upload this to Pixhawk.
[Firmware/src/modules/mavlink/mavlink_receiver.cpp : line 1351] /* if read failed, this loop won't execute */ for (ssize_t i = 0; i < nread; i++) { if (mavlink_parse_char(_mavlink->get_channel(), buf[i], &msg, &status)) {
/* --- REPORT HANDLING OF MESSAGE --- */
printf("\n");
printf("HANDLE MESSAGE\n");
printf("MSGID:%i\n",msg.msgid);
/* handle generic messages and commands */
handle_message(&msg);
Screen into the NuttX shell and start a mavlink session like in the example above.
On the off-board side, in another terminal run the c_uart_interface_example executable. You should see output in the NuttX shell similar to this:
HANDLE MESSAGE MSGID:76
HANDLE MESSAGE MSGID:84
(...)
HANDLE MESSAGE MSGID:84
HANDLE MESSAGE MSGID:76 Past this, you can:
Modify the received message data type Modify the sent message data type