Adriaan, Typical digital I/O pins can only read single ended values (the pin voltage is interpreted relative to the common ground reference). RS-422 is a differential signal measured between two wires, not relative to common ground. The Github example you mention below is specifically for a single ended electrical interface, the encoder only has a single data connection (D0). Your original specification mentioned the SSI line driver is RS-422, therefore you need an RS-422 to TTL converter. The clock signal may also be RS-422, check encoder datasheet. Arbitrary reference for a longer explanation: https://electronics.stackexchange.com/a/160552
Christo On Fri, Sep 11, 2026 at 9:55 PM Adriaan van Os <[email protected]> wrote: > > Christo, > > Thanks for the reply. > > > You need an RS-422 to TTL converter to read the absolute rotary > > encoder pulses, the diagnostics can be read by any digital input pin > > (after level shifting of course). > > Why is the converter needed ? Because of voltage differences ? This > example project <https://github.com/atarbabgei/absoluteEncoderSSI> seems > to connect the encoder directly to the Arduino. > > But I see lots of RS-422 to TTL converters on amazon.fr > > Thanks, > > Adriaan van Os >
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