Hello, I just received a PIXHAWK kit with 433 MHz 3DR V2 radios.
Following the instructions here, I connected one of the radios to port TELEM 1. I also attached the remaining peripherals, buzzer, button GPS/compass (using the I2C splitter). I did not, at this stage connect R/C.
I connected to a PC via USB, fired up Mission Planner and successfully connected, got GPS lock, IMU responses looked good etc. The LED on the radio did not turn on, but I assumed this was due to powering the board over USB since the 3DR radio guide states explicitly that:
"The radio will not connect unless the vehicle is powered"
Having done that, I connected the power module, connected the PC-side radio to the PC over USB (green LED came on started blinking as it looked for another radio) and powered the PIXHAWK with a battery.
The radio LED refused to come on. Through this post, I identified the GND and Vcc pins and measured the supply voltage: zero.
I measured the voltage on port TELEM2: 5.2V.
I disconnected the radio from TELEM1 and connected it to TELEM2 and it immediately paired with the PC radio. I tried Mission Planner and it connected immediately.
What is going on? Is there something wrong with my TELEM1 port? How could this be as the PIXHAWK is brand new? And why does the TELEM 2 port work exactly like the TELEM 1 should?
Scroll down to the section called CONNECTORS.
You will see that item 2 (Telem 2) is for radio telemetry (3DR telemetry radio). Item 3 (Telem 1) is for on-screen-display. I had the same problem. 3DR definitely needs to correct the documentation.
Phew, thanks a lot Mike, I thought I was going crazy. I would have thought that such a glaring discrepancy in the documentation would have generated a billion forum questions so was quite unnerved when I found nothing.