Connect to Vehicle Using Telemetry on Linux - linux

Question

I am having problems with connection to vehicle. First, I could not connect to the vehicle even with USB (I used "/dev/ttyUSB0" connection string and got an error). Later I got it working with connection string '/dev/serial/by-id/usb-3D_Robotics_PX4_FMU_v2.x_0-if00' and was able to send commands and receive response. Now I want to test it with the telemetry block connected to laptop USB. I tried the same way - with connection string "/dev/serial/by-id/usb-Silicon_Labs_CP2102_USB_to_UART_Bridge_Controller_0001-if00-port0", but it gives timeout message.
USB connection test output:
>>> PreArm: Check FS_THR_VALUE
>>> PreArm: Throttle below Failsafe
>>> APM:Copter V3.5.4 (284349c3)
>>> PX4: 0384802e NuttX: 1bcae90b
>>> Frame: QUAD
>>> PX4v3 0035003B 3136510A 34313630
Mode: STABILIZE
Autopilot Firmware version: APM:Copter-3.5.4
Autopilot capabilities (supports ftp): False
Global Location: LocationGlobal:lat=40.3985757,lon=49.8104986,alt=38.7
Global Location (relative altitude): LocationGlobalRelative:lat=40.3985757,lon=49.8104986,alt=38.7
Local Location: LocationLocal:north=None,east=None,down=None
Attitude: Attitude:pitch=-0.013171303086,yaw=0.0626983344555,roll=-0.0145587390289
Velocity: [-0.01, -0.01, 0.03]
GPS: GPSInfo:fix=3,num_sat=5
Groundspeed: 0.0168827120215
Airspeed: 0.263999998569
Gimbal status: Gimbal: pitch=None, roll=None, yaw=None
Battery: Battery:voltage=0.0,current=None,level=None
EKF OK?: False
Last Heartbeat: 0.967473479002
Rangefinder: Rangefinder: distance=None, voltage=None
Rangefinder distance: None
Rangefinder voltage: None
Heading: 3
Is Armable?: False
System status: STANDBY
Mode: STABILIZE
Armed: False
I am opening a connection like this:
vehicle = connect('/dev/serial/by-id/usb-Silicon_Labs_CP2102_USB_to_UART_Bridge_Controller_0001-if00-port0', wait_ready=True)
This results in the following traceback:
>>> Link timeout, no heartbeat in last 5 seconds
>>> No heartbeat in 30 seconds, aborting.
Traceback (most recent call last):
File "x.py", line 6, in <module>
vehicle = connect('/dev/serial/by-id/usb-Silicon_Labs_CP2102_USB_to_UART_Bridge_Controller_0001-if00-port0', wait_ready=True)
File "/home/seyid/.local/lib/python2.7/site-packages/dronekit/__init__.py", line 2845, in connect
vehicle.initialize(rate=rate, heartbeat_timeout=heartbeat_timeout)
File "/home/seyid/.local/lib/python2.7/site-packages/dronekit/__init__.py", line 2117, in initialize
raise APIException('Timeout in initializing connection.')
dronekit.APIException: Timeout in initializing connection.
Telemetry block is working when using MavProxy.
What is the problem here? Thank you

Answer 1

There are a couple of problems that can cause dronekit to fail with a connection timeout:
Ensure you have the pyserial module installed.
Specify the baud rate for your connection explicitly, as in:
vehicle = connect('/dev/ttyUSB0',
wait_ready=True,
baud=57600,
)
If connections with mavproxy to the same serial port work on your system it is likely that the second one is the culprit.