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@@ -57,3 +57,29 @@ When connected to the receiver with the transmitter, enter the ExpressLRS Lua sc
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+## SUMD Notes
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+SUMD is the Graupner HoTT bus protocol used to transmit multiple channel data over a single serial line. It transports up to 16 full res channels at a rate of 100Hz and is mainly used to provide digital channel data to Flybarless Control Systems for helicopters and older Flight Controllers.
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+As already stated many times in this manual, ExpressLRS expects AUX1 (channel 5) to control the arm state. This may lead to a conflict using serial protocols like SUMD in conjunction with devices having fixed channel assignments. To circumvent the problem, SUMD implements a channel remapping by swapping channels 5 and 8 in its serial output:
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+This opens the possibility to assign a linear output channel order for channels 1 to 7 using an appropriate OpenTX/EdgeTX mixer setup.
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+Example: Microbeast flybarless controller without RPM governor. (Follow the Microbeast manual to setup the single line receiver mode.)
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+Microbeast expected channel order for SRXL/SUMD:
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+Required OpenTX/EdgeTX mixer setup to satisfy the Microbeast expected channel order:
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