The flight controller I used is PIXHAWK 4 with APM firmware. The flight controller works on a quadroter UAV. I tried to connect the telemetry1 to the pi zero (air). Set the baudrate to 57600. Connect TX of the flighter controller to the RX of the pi zero. Connect the RX of the flight controller to the TX of the pi zero. Is there anyting wrong or I forget?
Sometimes ppl need a ground wire.
Also enable sr1 stream rates per the gitbook https://openhd.gitbook.io/open-hd/software-setup/telemetry-and-osd
If you see on the osd that the airpi temp and cpu load are changing then you at least have a link- openhd is capable of transmission (video transmission also confirms this obviously).
Try 115200 that is the default setting in the openhd-setting-1 file.
thanks , I have resolved this problem according the tutorial