Need a Telemetry radio option, not 900MHz

OK… I am looking for options for a short range telemetry solution. I have a small foam plane (Nano Goblin) that I am running a Matek405-CTR in. I woulds like to be able to use some sort of wireless telemetry solution for short range, really just need for adjusting settings and pre-flight setup/checks. I would normally use a small 900MHz telemetry radio, but the Nano Goblin is small, and I am using FrSky R9MM for the RC receiver, a 900 MHz system. Any suggestions?


If you are using FrySky Tx with open Tx and has like a X8R Rx, you can use Yaapu telemetry under 15 dollars. I think it also works with R9MM.

The yaapu cable weighs like 2 oz.

Well, if standard SiK radios are too big, you have a couple options.

  • in theory, yaapu script can setup to be able to change parameters, but that is not finished or stable yet. But it is perfect for checking status and get feedback during flight.
  • If you use 2.4 rx, you can stick to the 900Mhz SiK radios, they are based on HM-TRP modules, with a 3.3V regulator and a HM-TRP module you can have a 900Mhz radio (Antenna can be a piece of 1/2 Lambda wire) The catch is that you need a ST-Link programmer to upload Radio firmware for the HM-TRP module.
  • If you need only check and adjust parameters on the ground, you can use a simple serial-bluetooth module, it can provide connectivity for 5meters range.
  • If you move away from 2.4G radio, then an ESP based Wifi module (for example a CUAV PW-Link) also a good option, it provides around 20-50meter connection…

Agree on your Yaapu comment, overlooked he wants to change parameters.

Lost you on your comment, “ The catch is that you need a ST-Link programmer to upload Radio firmware for the HM-TRP module.”

Can you elaborate on this…

Sik Radios are basically a HOPE RF HM-TRP module but with a different firmware. Since original HM-TRP modules does not have the right bootloader, you need a ST-Link programmer to upload the bootloader and firmware for first time.

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Does this applies to all SIK radios or just 3DR or RFD also included?

All radios that based on the same Si1000 processor without rf amplifier. (all 100mW ones).

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Ok makes sense now. Thanks

Changing parameters would not happen much after initial tuning, likely. So a majority of time it will be downstream telemetry.

I have a ST-link programmer from one of the Dev boards I got for a ST microcontroller, so I should be able to program that if necessary, but would need to go to 433MHz, which is not a problem.

Try Yaapu…its amazing…i simply love it. Especially when I combine it with FrySky Lipo battery monitor.

There is nothing like that out there. It does work with R9MM

Yea, I am biased :slight_smile: Mission planner HUD inside my radio. Just awesome…

I’ve got a CUAV wifi telemetry module I havent tried yet, but out of the case (mine didn’t come with a case) it’s reasonably small.

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I use ESP8266 WiFi radios on many of my models for setup, configuration and short (very) range telemetry. It’s minuscule in size and weight and is ~$5. Logs can be downloaded but it’s slow. These are easily flashed with an FTDI adapter, after that it can be done OTA. I use the ESP-01 boards but there is more info here:

Hi @Eosbandi,
please could you point in the right direction how to write a bootloader on a HM-TRP using a ST-Link?
As far as I know I would need a “Silabs C2” programmer to do this.

I have a few bricked ones (without bootloader) which I would like to revive.
They seem to be made from “unobtainium” today.


Sorry, my bad. It needs a Silab C2 programmer indeed.

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Hi Andras,

No worries, thanks for the response.

@Eosbandi are you able to provide some assistance on programming the HM-TRP using the Silabs debug adapter?

Wiring diagram, softwares etc to do this?

Many thanks!

First, you need a C2 programmer, You can build one from an arduino (OlliW's Bastelseiten » owSilProg: AVR zum Flashen von Silabs Mikrokontroller & ESC)
Then upload bootloader and firmware from here
ArduPilot firmware : /SiK

I don’t find the pinout, but you can figure out the gnd/+3v3 and the data clock is 50% chance to get right at first (you have to use 3v3 to power the module). The programmer connections are the four holes on the panel beside the processor

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Thanks @Eosbandi I will be using an Silabs debug adapter instead of the Arduino route - do you have a suggestion for software to upload the firmware?

Hi @b_pickard

The wiring diagram can be found in the source code:

/// @page hm_trp_programming Programming the HM-TRP Board
/// The HopeRF HM-TRP board conveniently provides pads for programming
/// the Si1000.  These are the four 2mm-spaced holes next to the LEDs,
/// near the edge of the board ('o' in this picture).
/// +-----------~~
/// | O #:#:
/// | O = +------+
/// | O = |      |
/// | O   |      |
/// | O o +------+  <- C2CK
/// | O o     +-+   <- C2D
/// | O o # # | |   <- VDD_MCU
/// | O o     +-+   <- GND
/// +---^-------~~
///     |
///  This row of 4 holes.
/// The SiLabs programmer has a 10-pin ribbon cable, for which you will
/// need to make an adapter.  The User Guide, linked from the page here:
/// describes the pinout of the cable.
/// WARNING: The SiLabs adapter provides 5V on the USB Power pin.  DO NOT
/// connect this directly to the VDD_MCU pin on the HM-TRP module, or you
/// will (probably) destroy the chip.  If your HM-TRP board is mounted on
/// a breakout module that supports 5V input, you can connect USB Power
/// there.  If not, you must arrange for your own power supply, either by
/// adding a regulator to your cable or by using some other power source.
/// Connect the SiLabs debug adapter to the HM-TRP as follows:
/// Debug Adapter Pin:                 HM-TRP pin
///        2 <--------------------------> GND
///        4 <--------------------------> C2D
///        7 <--------------------------> C2CK
///       10 <-> 5V to 3.3V converter <-> VDD_MCU
/// @page hm_trp_hookup Connecting the HM-TRP Board

More can be found here.

Good luck!!

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