Channel Order

Many protocols, especially auto-binding Bind-n-Fly (BNF) protocols for small toys, require inputs on specific channels.

For convenience, and to support older radios which cannot change their output channel order, the MULTI-Module will automatically re-map channels 1-4 into the order required by the protocol, provided the channel order configured in the radio's mixer or outputs matches the MULTI-Module's Expected Channel Order.

This allows you to configure your all models using your preferred channel order, without having to worry about the actual channel order required by the model or protocol.

The channel order required for each protocol and sub-protocol is shown in each protocol's details page.

Channel order is particularly important for DSM receivers, which require channels in TAER order. If you use DSM, continue reading to learn how to correctly configure your model.

Expected Channel Order

In order for channel re-mapping to work, the MULTI-Module must receive channel data in a known order. This is the Expected Channel Order.

The Expected Channel Order is set in the MULTI-Module firmware when it is compiled.

The default MULTI-Module Expected Channel Order is AETR.

With OpenTX v2.3.4 or newer, and MULTI-Module firmware v1.3.0.45 or newer, the MULTI-Module's Expected Channel Order is displayed on the Module Status line in the Model Setup screen.

Module Status showing Channel Order

You should update your MULTI-Module's firmware if the Expected Channel Order is not displayed in the Module Status line. Updating the firmware will ensure that you know the Expected Channel Order.

When configuring a model, the channel order in the Mixer should be the same as the Expected Channel Order.

Mixer with inputs assigned in AETR order

When the MULTI-Module transmits to the example model configured above, configured for AETR using the DSM protocol, the module will re-map the channels to TAER order prior to transmission.

Channel Re-Mapping Examples

Example 1

• The MULTI-Module is using the default Expected Channel Order AETR

• The protocol is DSM, which requires channel data in TAER order at the receiver

• The model is configured in the radio with channels in AETR order in the mixer/outputs

• Servos and motors are plugged into the labelled outputs on the receiver, in TAER order

In this case the MULTI-Module re-maps the channels before transmission, the receiver receives TAER, and everything works as expected:

Radio CH	Radio Mixer	Module Re-mapping	Receiver Receives
1	Aileron	1 -> 2	Throttle
2	Elevator	2 -> 3	Aileron
3	Throttle	3 -> 1	Elevator
4	Rud	4 -> 4	Rudder

Example 2

• The MULTI-Module has been updated to use the Expected Channel Order TAER

• The protocol is DSM, which requires channel data in TAER order at the receiver

• The model is configured in the radio with channels in TAER order in the mixer/outputs

• Servos and motors are plugged into the labelled outputs on the receiver, in TAER order

In this case the MULTI-Module does not need to perform channel re-mapping and everything works as expected:

Radio CH	Radio Mixer	Module Re-mapping	Receiver Receives
1	Throttle	1 -> 1	Throttle
2	Aileron	2 -> 2	Aileron
3	Elevator	3 -> 3	Elevator
4	Rudder	4 -> 4	Rudder

Example 3

• The MULTI-Module is using the default Expected Channel Order AETR

• The protocol is DSM, which requires channel data in TAER order at the receiver

• The model is configured in the radio with channels in TAER order in the mixer/outputs

• Servos and motors are plugged into the labelled outputs on the receiver, in TAER order

In this case the MULTI-Module re-maps the channels, but because the input order is not as expected, the output order is incorrect and the model does not work:

Radio CH	Radio Mixer	Module Re-mapping	Receiver Receives
1	Throttle	1 -> 2	Elevator
2	Aileron	2 -> 3	Throttle
3	Elevator	3 -> 1	Aileron
4	Rudder	4 -> 4	Rudder

Mismatching the radio channel order and the MULTI-Module's Expected Channel Order can have potentially disastrous or dangerous consequences!

The scenario in Example 3 can be avoided by:

• Changing the model's channel order in the mixer/outputs to match the MULTI-Module's Expected Channel Order

• Changing the MULTI-Module's firmware to expect TAER instead of AETR

• Disabling Channel Re-Mapping in Model Setup

Changing the Expected Channel Order

If you prefer to configure your models with a different channel order, you can change the Expected Channel Order by flashing different firmware to your MULTI-Module.

You can compile your own firmware, or download a firmware image with a different Expected Channel Order from the GitHub releases page.

MULTI-Module firmware downloads are available for AETR, TAER, and RETA channel orders, see the Firmware Files page.

Changing the Radio's Default Channel Order

Once you have settled on a preferred channel order, and flashed your MULTI-Module with firmware which expects that order, you should:

1. Change the Default channel order setting on your radio to match the MULTI-Module's expected order

2. Ensure that any models which you control with the MULTI-Module are configured with the channel order which the MULTI-Module expects

Radio Default Channel Order set to AETR

Changing the radio's Default channel order only affects new models - you must manually edit any existing models.

The Mode setting reflects the hardware setup of the radio's sticks. Do not change the Mode unless you physically change the sticks, e.g. switching the throttle from the left to the right stick.

Disabling Channel Re-Mapping

As of MULTI-Module firmware v1.3.0.45 and OpenTX 2.3.3, channel re-mapping can be disabled for a model by checking the Disable Ch. map box in Model Setup.

You can disable channel re-mapping If you prefer to configure the channel order yourself, or if channel re-mapping is causing problems due to a mismatch between the order in the model and the MULTI-Module's expected channel order.

Channel Mapping Disabled

When channel re-mapping is disabled the channel data will be transmitted to the receiver in the exact order it is configured in the radio's mixer or outputs.