DIY-Multiprotocol-TX-Module/docs/Transmitters.md

Compatible Transmitters

There are two different options for the interface between the Mulitprotocol Module and the transmitter: PPM and Serial. The considerations are different for each.

• PPM is more generic, easy to implement and will work with most transmitters.
• Serial requires custom firmware on the transmitter but brings added functionality including protocol selection through the Tx interface.

Any Tx that provides a PPM output (like a trainer port, or a transmitter with a RF module bay) is compatible with the MULTI-module. In practice, most of the documentation on this site is focused on building modules that slip into your transmitter’s module bay.

##PPM The DIY Mulitprotocol module supports industry standard PPM interface that works with all transmitters with either a module bay, and/or a trainer port. Even the older 72MHz FM radios support this standard.

When using the standard PPM Tx output, the protocol selection is achieved through a 16 position rotary switch on the module. This enables 15 protocol/sub-protocol/options combinations to be selected. Binding is achieved by pressing a bind button on the back of the module (see picture below)

Since the module supports literally hundreds of protocol/sub-protocol/options combinations, you must select which of these will map to the 15 positions on the switch. Refer to the Compiling and Programming page for information on how to do his.

Even in PPM mode it may still be possible to access telemetry information from selected receivers that support telemetry (e.g. Frsky, Hubsan, DSM). To find out more about this advanced option check out the section on the Advanced Topics page.

For transmitter setup using the PPM protocol go to the PPM Setup page

##Serial Transmitters that run er9X, erSky9X or OpenTx firmwares - like the FrSky Taranis and FlySky TH9X/Turnigy 9X/R family of transmitters - have the option of using a fast, two-way serial, communication protocol between the Tx and the DIY Multiprotocol module. Using this serial communication protocol has some significant advantages:

1. selecting the specific radio protocol (e.g. DSM) and the sub protocol (e.g. DSMX) directly in the menu system of the Tx (see the picture below)
2. binding through the menu on the Tx
3. range checking through the menu on the Tx
4. in some cases enabling two-way telemetry for telemetry capable receivers and protocols.

This serial protocol does not require any hardware modifications, but will require updating the firmware on your radio.

To enable serial telemetry may require modifications to your Tx. See the table below.

Transmitters and firmware combinations that support the Serial protocol are:

Transmitter	Firmware Options	Telemetry Enabled
FrSky Taranis/Plus/9XE	erSky9x, OpenTx 2.1.8 Multi	Yes - native
Turnigy 9X/9xR	er9x	Mod required, No DSM telem
Turnigy 9XR-Pro	erSky9x	Yes - native
FrSky TH9x	er9x	Mod required, No DSM telem
SKY board	erSky9x	Yes - native
AR9X board	erSky9x	Yes - native
9Xtreme board	erSky9x	Yes - native
AR9X UNI board	erSky9x	Yes - native

Click on your transmitter above to view specific setup instructions.

##Optional Telemetry mod for 9X/r TH9X transmitters The telemetry mod for these transmitters has evolved. The original and popular "FrSky Telemetry Mod" requires 2 pins on the transmitter module board to be modified (RX on pin 5 and TX on pin 2). All the recent MULTI-Module hardware options supports serial transmission on pin 1 (the same pin as the PPM signal) so, in this case, only the mod on pin 5 is required.

A good tutorial to follow is Oscar Liang's here but when you get to wiring up the Tx Module bay pins, you only need to perform the steps relevant for Pin 5.

You can see Midelic's original instructions here

##Other Notes:

• er9X and erSky9X firmware already supports Multiprotocol Module as a standard feature. At time of writing it looks like that the next major release of OpenTx - OpenTx 2.2 - will have DIY Mulitprotocol support as a standard feature.

• Owners of Walkera Devo transmitters should look at the Deviation-Tx project for how to achieve the same end goal with your transmitters.

• To enable telemetry on a Turnigy 9X or 9XR you need to modify your TX following one of the Frsky mod like this one.

• DSM telemetry is not available on er9x due to a lack of flash space.

• Enabling telemetry on a 9XR PRO and may be other TXs does not require any hardware modifications. The additional required serial pin is already available on the TX back module pins.

• Once the TX is telemetry enabled, it just needs to be configured on the model (see er9x/ersky9x documentation).