How to receive GPS information in voxl-tflite-server?

Nguyen Tien Su

I need to have GPS information such as latitude, and longitude, ... to process in voxl-tflite-server c++ code. How can I do it?

Matt Turi

Hello @Nguyen-Tien-Su,

voxl-inspect-gps (https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-mpa-tools/-/blob/master/tools/voxl-inspect-gps.c) is an example of how to subscribe to the gps pipe and process the data.

Nguyen Tien Su

Thank you, @Matt-Turi !
I checked the code and understood. But it's error when I include mavlink.h header file from c_library_v2 library into voxl-tflite-server. It said that mavlink.h file not found. How can I solve this problem?

Matt Turi

To use the mavlink headers, you must add voxl-mavlink to the required dependencies for the project. This can be done by modifying the install_build_deps.sh script, and simply adding voxl-mavlink to the DEPS_* list depending on your platform.

DEPS_QRB5165="
libmodal-pipe
libmodal-json
voxl-opencv
voxl-mavlink  
qrb5165-tflite"

DEPS_APQ8096="
libmodal-pipe
libmodal-json
voxl-opencv
voxl-mavlink
apq8096-tflite"

Nguyen Tien Su

Thank @Matt-Turi very much !
I am successful to receive GPS in voxl-tflite-server. But I can't open 2 pipes GPS and TFLITE at the same time since they use same channel 0. Their channel seems to be set up by the MPA and can't change. How can I solve this problem?

Matt Turi

@Nguyen-Tien-Su,
Did you experience any error messages when you tried this? Subscribing to the gps pipe should be independent of any channels/pipes that the tflite-server opens, as gps is a client connection. See here: https://gitlab.com/voxl-public/voxl-sdk/services/voxl-tflite-server/-/blob/master/src/main.cpp#L344 for an example of opening up a client connection and getting the next avaialble channel automatically using

int ch = pipe_client_get_next_available_channel();

Nguyen Tien Su

Hi @Matt-Turi ! This is error.

I tried to change the channel of GPS, then I can't receive any GPS message. I also tried to change channel of the TFLITE server but it couldn't start.

Matt Turi

Make sure you are setting the callback functions correctly with the next available channel (rather than hardcoding to 0). The tflite-server is only opening one client connection to receive camera frames, so it should be simple to avoid a channel conflict.

If your callback functions are named the same as the inspect-gps example, this code could be pasted in after line https://gitlab.com/voxl-public/voxl-sdk/services/voxl-tflite-server/-/blob/master/src/main.cpp#L354

int ch = pipe_client_get_next_available_channel();

pipe_client_set_simple_helper_cb(ch, _helper_cb, NULL);
pipe_client_set_connect_cb(ch, _connect_cb, NULL);
pipe_client_set_disconnect_cb(ch, _disconnect_cb, NULL);

int ret = pipe_client_open(ch, GPS_RAW_OUT_PATH, PROCESS_NAME, \
          EN_PIPE_CLIENT_SIMPLE_HELPER | EN_PIPE_CLIENT_AUTO_RECONNECT, \
	  sizeof(mavlink_message_t));

Nguyen Tien Su

Hi @Matt-Turi !
You right. I hardcoded tflite server channel, so I forgot to change it when setting callback function. Now, my code works fine.
Thank you very much for your enthusiastic help!