DT Receivers - Serial Outputs


This page relates to receivers with v2x and v3x programs (Rx3x/Rx2x receivers). v6x program is slight different.

Many DT receivers can output multi-channel data on one pin, usually for quadcopter type models, UAV's, robotics, etc. Two types are available, Serial and Sequential PPM (SumPPM/CPPM). Outputs/data for channels that the transmitter does not control are meaningless.
* Servo outputs are determined by the number of physical pads enabled, one channel per pad.
* SumPPM is always 7 channel. Many receivers have two outputs; one idles high and the other idles low.
* Serial is always 7 channels except for Rx32d. Up to v352 Rx32d outputs 7 channel serial. From v353 Rx32d outputs 9 channel serial. Rx32d-18S is intended for use with 18ch X-Plus so outputs 18 channel serial. Serial has two start bytes 0xfe/0x02 from v353.

Rx32d: Changing between 7 and 9ch outputs is likely to need rebinding.



7ch SERIAL:



- 16 or 18 byte RS-232 serial output at 115200 baud, 8 bit, no parity, 2 stop bits, LSB first.
- Byte 1: 0xFE first start byte (from v353)
- Byte 2: 0x02 second start byte (from v353)
- Byte 3: Checksum - sum of other 15 bytes cast to 1 byte (8 bit)
- Byte 4: Signal quality - 1st bit (MSB) 1=new data, 0='hold' data/signal not validated; next 2 bits not used; last 5 bits (LSB) = RSSI (31 max, 0=no signal/timeout)
- Bytes 5-18: Payload - 7 channels, 2 bytes per channel - 1st 3 bits not used, next 3 bits = channel number, last 10 bits = channel position
- Frame rate is 22ms

The two start bytes 0xfe/0x02 exist only from v353. These are not shown on the above screen prints but are illustrated on the 9ch and 18ch examples below.




9ch SERIAL: (Rx32d from v353)


- 22 byte RS-232 serial output at 115200 baud, 8 bit, no parity, 2 stop bits, LSB first.
- Byte 1: 0xFE first start byte
- Byte 2: 0x02 second start byte
- Byte 3: Checksum - sum of other 19 bytes cast to 1 byte (8 bit)
- Byte 4: Signal quality - 1st bit (MSB) 1=new data, 0='hold' data/signal not validated; next 2 bits not used; last 5 bits (LSB) = RSSI (31 max, 0=no signal/timeout)
- Bytes 5-22: Payload - 7 channels, 2 bytes per channel - 1st 3 bits not used, next 3 bits = channel number, last 10 bits = channel position
- Frame rate is 22ms



18ch SERIAL: (Rx32d-18S, Rx38)



- 40 byte RS-232 serial output at 115200 baud, 8 bit, no parity, 2 stop bits, LSB first.
- Byte 1: 0xFE first start byte
- Byte 2: 0x02 second start byte
- Byte 3: Checksum - sum of other 37 bytes cast to 1 byte (8bit)
- Byte 4: Signal quality - 1st bit (MSB) 1=new data, 0='hold' data/signal not validated; next 2 bits not used; last 5 bits (LSB) = RSSI (31 max, 0=no signal/timeout)
- Bytes 5-40: Payload - 18 channels, 2 bytes per channel - 1st bit not used, next 5 bits = channel number, last 10 bits = channel position
- Frame rate is 22ms




7ch SEQUENTIAL PPM:



- 7 channels ~0.9 to 2.1ms, 1.5ms neutral
- 300us start/stop pulses; either edge can be used for triggering
- 'v3 software only has fixed numeric sort order (0-Throttle, 1-Aileron, 2-Elevator, 3-Rudder, 4-Gear, 5-Aux1, 6-Aux2)
- 'v2' software has options for fixed numeric and for the order to be as supplied by the Tx
- Frame rate is 22ms




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