DSM - MULTI-Module Documentation

Details
Protocol Number:  6
Autobind:  No
Channel Re-mapping:  Yes
Extended Limits:  Yes
Failsafe Support:  No
Receiver Match:  Yes
Telemetry:  Yes - for TSSI and plugins
Option Value:  Number of channels (3 to 12)
Notes
Models:  Spektrum DSM2 and DSMX compatible receivers
Unless Channel Re-mapping is disabled, the radio model's channel order must match the Expected Channel Order of the MULTI-Module, which is AETR by default.  See the Channel Order page for more details.
Autodetect Format
Autodetect Format (a.k.a. the Auto sub-protocol) allows the radio to negotiate the correct protocol (DSM2 or DSMX), the correct number of channels, and the optimal data rate with the receiver.  Auto-detection relies on telemetry working between the radio and the receiver.
When binding, Autodetect Format is strongly recommended to ensure that the optimal configuration for the receiver is used.
If autodetection isn't working properly with your receiver (for example the number of channels is set incorrectly), you can un-check Autodetect Format and manually select the sub-protocol and number of channels.
Binding
For best results, set the sub-protocol to Auto for binding.  During the bind process the receiver will inform the radio of the optimal configuration for sub-protocol, number of channels and refresh rate.  When the bind ends the sub-protocol should have changed to one of the four DSM2 or DSMX options.
If binding using the Auto sub-protocol fails, and the sub-protocol remains on Auto, the radio was not able to negotiate the settings with the receiver.  Try moving the radio closer or farther away from the receiver and trying again.
If you are unable to bind in Auto mode you can try all four sub-protocols manually.
When manually selecting the sub-protocol, your receiver may work correctly with more than one of them, or it may work correctly with one and erratically or not at all with others.
Take care when testing sub-protocols and ensure your model is safe (e.g. propellers off).
Channel Order
Channel order is very important for DSM, and a common source of problems if not configured correctly.
By default the MULTI-Module will expect channels in the module's Expected Channel Order, and will convert them into TAER order automatically.
The model's channel order must match the Expected Channel Order of the MULTI-Module, which is AETR by default.  See the Channel Order page for more details.
Unless you change the firmware on your MULTI-Module, your model should be configured with the channels assigned in AETR order, because this is the default Expected Channel Order.
Channels in AETR Order
If you change the firmware to expect a different channel order you must change the radio's default channel order and manually update any existing models.
See the Channel Order page for more details, including how to disable channel order remapping.
Option Value
Sets the number of channels for the receiver (3-12).  The value is set automatically when using Autodetect Format or the Auto sub-protocol during binding.
Receiver Output Range
By default the MULTI-Module will scale receiver output to match the Spektrum standard throw, 1100µs to 1900µs.
Either one of the methods below can be used to increase the output range.  Usually one method is sufficient, but both methods can be combined to give even greater ranges or more customization if required.
Method 1 - Enable Max Throw
The easiest way to increase output ranges is by checking Enable max. throw in the model setup.  This will increase the output range of all channels to 1024µs to 1976µs.
Enable max. throw
With Enable max. throw checked:
The default weight of 100% will now give an output range of 1024µs to 1976µs
A weight of 84% will give the Spektrum standard range of 1100µs to 1900µs
Method 2 - Extended Limits
Alternatively, output range can be increased by enabling Extended Limits in the model setup and configuring minimum and maximum output percentages for each channel in the Outputs.
This method allows each channel's range to be configured independently, and allows larger ranges than Enable Max Throw.
Extended Limits Enabled
With Extended Limits enabled:
A range of -100% to 100% will give an output range of 1100µs to 1900µs
A range of -125% to 125% will give an output range of 1000µs to 2000µs
A range of -130% to 130% will give an output range of 980µs to 2020µs
CH3 Output Range Extended to +/- 125%
If you are using PPM Mode, ensure that the PPM_MIN_100 and PPM_MAX_100 settings in _Config.h match your radio's output.
SAFE Select
To allow SAFE to be ON with a switch assignment you must remove the bind plug after powering up the RX but before turning on the TX to bind. 
If you use Autodetect Format during binding the MULTI-Module will choose DSMX 11ms and Channels 1-7 (change channels to 1-9 if you wish to assign switch above channel 7). 
In order to use the manuals diagram of both sticks 'Down-Inside' to set a SAFE Select Switch Designation, you must have Throttle and Elevator channels set to Normal direction but the Aileron and Rudder set to Reverse direction. 
If setting up a new model with all channels set to Normal you can hold both sticks 'Down-Outside' to assign the switch with 5x flips. This has been tested on a Mode 2 radio.
Servo Refresh Rate
Servo refresh rate is 22ms unless 11ms is selected.  The option to select the refresh rate when binding will be available in OpenTX 2.3.10+.
Telemetry Range
Some DSM receivers and many bind-and-fly (BNF) models with DSM receivers (e.g. E-flite UMX models) have 'fly-by' telemetry which has very limited range (less than 100' or 30m).
Short-range telemetry is not a problem with the MULTI-Module or radio, it is a limitation of the receiver.
To avoid unnecessary 'telemetry lost' warnings when using a short-range-telemetry receiver, disable the telemetry warnings by checking the Disable telemetry alarms checkbox in the model's Telemetry configuration.
Telemetry Alarms Disabled
For protocols other than DSM, checking Disable telemetry alarms will generate a warning when the model is activated.  This warning is not shown when the MULTI-Module protocol is DSM.
Always perform a  manual Range Check to ensure that control range will be sufficient for your needs.
Throttle Kill
Throttle Kill is available on CH14 for models which need it (X-Vert, Blade 230S, etc.).  The output value in is derived from the weight applied to CH14, which must be between -50% and -100%
A weight of -50% gives 1100µs output
A weight of -80% gives 980µs output
A weight of -100% gives 904µs output
An output weight of -80% on CH14 will instantly stop the motors on an X-Vert by setting the throttle channel to 980µs (equivalent to -130% on a Spektrum radio).
For example, CH14 is configured with a weight of -80%, switch SF as the source, and SF↓ as the switch
X-Vert -130% Throttle Kill on CH14 using switch SF
When switch SF is off, CH14 is at 0%
When switch SF is on, the MULTI-Module sends 980µs on the throttle channel, killing the motors
Channel Assignment
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
CH9
CH10
CH11
CH12
CH13
CH14
A
E
T
R
CH5
CH6
CH7
CH8
CH9
CH10
CH11
CH12
-
Throttle Kill
The Channel Assignment table assumes the MULTI-Module's default Expected Channel Order, AETR, is being used on the radio.
If you have changed the MULTI-Module's Expected Channel Order to something other than AETR you need to adjust CH1 to CH4 accordingly. See the Channel Order page for more details.
Sub Protocols
0 - DSM2 1F
DSM2, resolution 1024, servo refresh rate can only be 22ms.
Note: 'DSM2 1F' was previously labelled as 'DSM 2 22ms'.
1 - DSM2 2F
DSM2, resolution 2048, servo refresh rate can be 22ms or 11ms.  All servo outputs will be 22ms when more than seven channels are configured.
Note: 'DSM2 2F' was previously labelled as 'DSM 2 11ms'.
2 - DSMX 1F
DSMX, resolution 2048, servo refresh rate can only be 22ms.
Note: 'DSMX 1F' was previously labelled as 'DSM X 22ms'.
3 - DSMX 2F
DSMX, resolution 2048, refresh rate 22ms or 11ms.  All servo outputs will be 22ms when more than seven channels are configured.
Note: 'DSMX 2F' was previously labelled as 'DSM X 11ms'.
4 - Auto
The Auto sub-protocol enables the radio to negotiate the correct settings for the receiver.  Auto-negotiation is supported on OpenTX, erSkyTx, and er9x.
In OpenTX, Auto can be enabled by checking the Autodetect format box or selecting the Auto sub-protocol.
You must have telemetry enabled and working, and on erSkyTx you need to set the telemetry Usr proto to DSMx.