MPM Lite Multi-Protocol Module for X-Lite Review

July 26, 2018 15:54 | By | Add a Comment

The MPM Lite promises instant compatibility with DSM-2/DSM-X, Futaba SFHSS and a range of other systems for the FrSky X-Lite. Does that even work? Read on after the break!

The X-Lite has quickly become a favorite on the field, not only due to its small size and light weight, but also due to the fact that OpenTX is pretty much unhindered by product categorization concerns. There’s no manager telling the developers to cut a certain feature from a low-range model because they want to sell a high-priced one. So far, the only real drawback was the lack of wireless trainer functionality, and the problem of this being yet another system. If you already fly FrSky, great. But what if you have a ton of Spektrum models, or you used a Walkera Devo radio before, or you use one of the popular FlySky transmitters and already have a whole bunch of receivers for your old system?

Enter the MPM Lite. Based on an open source design by the DeviationTX Project and Pascal Langer, this module slides right on to the back of the X-Lite, and immediately adds compatibility with the following systems:

Manufacturer RF Chip Example Protocols
Cyprus Semiconductor CYRF6936 DSM-2/DSM-X
Walkera Devo
J6Pro
Texas Instruments CC2500 FrSky
Futaba SFHSS
Amiccom A7105 FlySky
FlySky AFHDS2A
Hubsan
Nordic Semiconductor NRF24L01 HiSky
Syma
ASSAN
and most other Chinese models

A standard 2dB rubber duck antenna comes standard, but you can also install the FrSky 5dB whip, 7dB patch, or any other antenna with a RP-SMA male connector.

We tested DSM-X, Walkera Devo, FlySky and Hubsan, and they all worked perfectly. Usage is dead simple: You activate the external transmitter option for your current model in OpenTX, select the system you want to use, protocol subtype if applicable, and press bind. Note that for DSM-2 and DSM-X, one common cause for bind failure is the transmitter being too close to the receiver. If you can’t seem to bind no matter what you do, move them apart a little, or install a smaller, lower-gain antenna.

Well… almost. There’s a few things to consider. While the device comes with firmware installed, the manual states that it doesn’t. Fine, we thought, never change a running system. As it turns out we ended up flashing the firmware regardless, because there’s an issue regarding the PPM control output value range.

On normal transmitters, you can pretty much achieve anywhere from 1000 to 2000us PPM control output. This is important for multicopter flight because software like Betaflight doesn’t allow you to arm the quad if your throttle is not below a certain point. You can adjust the stick endpoints to some degree, but the MPM-Lite produced output that ranged from 1200 to 1800, and it was not possible to get around this. In fact, the X-Lite output 998us as the lowest value, but the MPM-Lite did not go below 1192 on any channel. Upping the throw on the X-Lite to 120% did not help either.

Luckily flashing the firmware is relatively easy thanks to the integrated USB port on the module: Just download the Arduino IDE, download the latest firmware version (which also contains needed USB drivers for the “Maple003 DFU Device”), and follow the instructions for flashing the STM32 version of the software. In the file _Config.h you want to uncomment the line

#define DSM_MAX_THROW

This will give you output values from 1090us to 1910us, which is enough to be able to arm Betaflight.

What’s especially nice is that the case and connector is modular too, so it’s very easy for anyone to create their own modules for the X-Lite. The pinout is actually identical to the standard JR module connector, so even third party long range systems could easily be connected and used.

Here is a close up of the board with all the RF chip goodness. Apparently there were provisions for some shielding over the HF part, but it seems there wasn’t enough room in the case. It’ll be interesting to see whether this will be improved in a future version.

 

The antenna connector is very fragile. In general, disassembling this module isn’t really recommended, unless you need to get to the internal serial programming pins that are helpfully marked on the board.

The only complaint that comes to mind is the fact that this module attaches and detaches quite easily. It does fit securely, but you do not want to push it upwards while you have a model in the air. Thankfully, reattaching it does restore control should you manage to do this during flight.

In general, this module is a winner. The price is relatively high at about 40-50 USD, but it’s lightweight and just works. You don’t get antenna diversity with this one, but attaching a high gain antenna can remedy that to some extent. And if you want to use a more robust protocol with better telemetry support, there’s always the option of buying more FrSky receivers.

 

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