Protocol decoder:graycode

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Pd graycode.png
Name Gray code and rotary encoder
Description Accumulate rotary encoder increments, provide timing statistics.
Status supported
License GPLv2+
Source code decoders/graycode
Input logic
Output graycode
Optional probes D0-D7
Options numchannels, edges, avg_period

The graycode protocol decoder can decode Gray Codes up to 8 data lines (but easily generalizes). One popular special case is the Rotary Encoder, which has two lines, A and B, representing a quadrature signal. The decoder will report phase, counting direction, absolute count, as well as timing information.


edges: Number of rising and falling edges per turn of all lines. Rotary encoders are usually labeled as having N pulses per turn. A pulse consists of rising and falling edge and you have two lines that are phase-shifted by 90° to one another. This allows to extract 4N edges per turn.

numchannels: due to a current bug in Pulseview, assigned optional probes aren't reported correctly, so you'll have to select the number of channels manually.