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DX18 Compatibility Mode
Overview:
DX18 Compatibility Mode should only be used when importing a file from a DX18 into a modern radio when nothing in the aircraft is being updated. If you are creating a new model, or are updating the receiver in an existing model, set DX18 Compatibility Mode to Inhibited and configure the channel behaviors correctly. Enabling it will likely cause confusion, as you have to configure channels 13 and 14 to make 11 and 12 do something. For best results use the native mode of your transmitter whenever possible.
NOTE: As of Airware version 4.00 for IX and NX radios, channels X+1 and X+2 are renamed to Aux13 and Aux14 respectively. They have the same limitations on speed and resolution as X-Plus channels. Only the name has changed. This document uses the both old names and new names as it bridges between old radios and new.
Background:
DX18 Compatibility Mode was originally developed to allow early DX18 users to drive 12-channel receivers. Today it is intended solely for backwards compatibility of new radios to old receiver installations. It should be disabled in new builds.
In the DX18 the user would need to configure channels X+1 and X+2 in order to drive channels 11 and 12. The DX18 did not have a native mode for 12 channel operation, and this was the work-around. In a 14- or 20-channel transmitter with DX18 Compatibility Mode turned on, it will behave the same way as a DX18 did. That is, the user would have to configure channels 13 and 14 to drive channels 11 and 12. This can be confusing, to say the least.
If DX18 Compatibility Mode is disabled, channels 11 and 12 will use the data configured for them by other screens in the radio, the same as for all other channels. This is the default mode.
How to Use It:
When a file with DX18 Compatibility Mode enabled is imported into a 14- or 20-channel radio, the radio will honor the settings and control 11 and 12 using the X+1 and X+2 settings (Aux13/14). Any settings made for channels 11 and 12 will be IGNORED because the DX18 Compatibility Mode setting is telling it to use X+1 and X+2 (Aux13/14) instead.
If the user wishes to use a DX18 file on a 12-channel receiver and be able to configure channels 11 and 12, he will need to first disable DX18 Compatibility Mode, then set up channels 11 and 12 manually to match what used to be sent to X+1 and X+2 (Aux13/14). This is quite simple now using the Channel Assign screen in the latest Airware for IX/NX radios.
When a file with DX18 Compatibility Mode disabled is imported into a 14- or 20-channel radio, the settings for all channels will act as expected for normal channels.
DX18 Compatibility is Related to Frame Rate:
DSMX can operate in several modes:
• “Hybrid 11/22ms” - 10 channels: 4 of them at 11ms and 6 at 22ms
• “12@22+8@Var” - 20 channels: 12 channels at 22ms and 8 channels (X-Plus, Aux13-20) at variable refresh rate
• “14@22ms” - 14 channels at 22ms (not supported by all receivers)
After you import a file with DX18 Compatibility Mode enabled, you should verify that the Servo Mode is set to “12@22+8@Var” so that the channels all go out.
Because of the way DSMX works, if you configure your 14- or 20-channel transmitter to operate in 11ms mode, it will only drive 10 channels. The new Frame Rate screen on NX and IX transmitters shows you the update rate of each channel as 11ms, 22ms, Variable, or N/A (which indicates it is not sent to the receiver). 11ms and 22ms are sent at full resolution (2048) while Variable channels are sent at 512 resolution. The resolution is the number of discrete steps between -150% and +150% of travel.