HC-12 Telemetry Getting Params not working

I am using the hc-12 module and an omnibusf4pro board. I have one hc12 connected to SERIAL1 and the other to my computer via an ft232 usb-uart converter. Both hc12’s are at the same speed (9600 baud) and can communicate with eachother (verified by creating a loop with the ftdi and both hc-12’s, both can receive and transmit). When I connect the Getting Params part doesn’t progress, or gets stuck at the first parameter. If i say cancel i can receive telemetry data (gps position, attitude…), but i cannot send any commands or write waypoints (when i say write waypoints I just get “unexpected error”). I have also realised that the receive led on the ftdi is solid on while the transmit led pulses every second (HUD update frequency I assume). Is my baud rate too low (I can go up to 115200 but i didn’t try because the range drops a lot), do i need to do something with cts/rts or ecc (I think these are for 3DR systems as the hc-12 doesn’t have cts/rts pins but I don’t know)? My parameters are here (I have set SERIAL1 baud rate to 9600 and protocol to Mavlink2):
Omnibus F4 Pro 13-05-2020.param (19.5 KB) Thanks in advance for your attention and help.

Update: Problem is now fixed, I have increased baud rate to 57600, sacrificing some range. everything from writing waypoints to fetching parameters are working now. It seems to be an issue of throughput.


great news that these work on ardupilot, i have a few of them i bought for something else that never got built and was wondering if i could use them for mavlink telemetry!

What range are you getting out of them, especially at ground level and are you using an external antenna on the u.fl/ipx connector?

I used the spiral antenna that comes in the bag. I haven’t really done propper range testing but there is a datasheet on one of these that give out some numbers here. So judging by this datasheet i should be getting around 125 meters or so of range. If you’re going to use these modules you should make sure that both the recieving and transmitting antennae should remain mostly parallel, as they are linearly polarised and are horrible when tilted. I got 10m or so of usable range when they were 90 degrees apart. My field data fits the theory described here. I’d suggest getting an external antenna on it, circularly polarised if you can manage, or align the linearly polarised ones propperly if not. Please update us on the results. Good luck!

These modules should be good for 1000+ m with ease in the air with a decent antenna, having to wait to test as it tirns out i only have one pigtail in the right sma socket for the 433 mhz antennas i own grrr.
That normal mode helical they come with is not something I ever planned on using because of how poor they are and will either use a straight whip or a bigger normal mode helical.

CP is bad for range, CP looses 1/5 of the range for a given power level over a linear antenna, I fly my video mainly on linear because of the much better range, I’ll stick with linear.

Do they automatically re connect on signal recovery after a loss like the 3dr/sik radio modules do?

Something I forgot to ask, is there any configuration software for these modules or is it all done through AT commands?


EDIT: just found a config program :slight_smile:

They are very simple stuff. They send and recieve serial messages without any acknowledgement. Kinda like UDP packets. If the reciever recieves it then it goes through. If it cannot the packet is dropped. If a dropped packet can result in a disconnect from mission planner i don’t think they reconnect. But from what i’ve seen is when they get out of bounds you just start getting less and less packets. No sudden loss of connection. Also they are (to my knowledge) only configured through AT commands so you will need a UART-USB converter. The AT commands are detailed in the datasheet i have linked above. Have a good one

9600 is just too low for Mavlink to work in my experience. 19200 will work most of the time, albeit slow. 38400 or 57600 better, though, but range suffers with 57600.

IIRC, the HC-12 Mavlink-link (?) will reconnect automatically.