Encoder Index Signal Debugging

Hey, I’m making a modified version of this using Moteus drivers with some custom firmware to handle the 20,000 PPR encoder output, instead of the ODRI design.

One of the issues that’s really killing me at the moment is the index signal from the encoder, I have an encoder powered on, connected to nothing else (as in, +5v, GND, and my oscilloscope). I get a clean A/B signal but only a sporadic index signal, on some of my encoders. Others work completely fine, sending an index pulse every rotation.

I’ve tried changing wheels, changing encoder, different wires… And all of my fresh batch of encoders seem to have the same problem, perfect A/B signals, no index signal, which heavily suggests that the issue is not with the encoder itself. Encoder wheels are clean, mechanical assembly is rigid (and again, works for 9 of my other joints)… I noticed in one case that one of my motors had melted the casing and angled the encoder by 5-10 degrees, but after fixing that the problem remains.

Do you have some recommended additional debugging tips for this, or issues I might have overlooked?


Are you sure the codewheel are mounted on the right side? The index pulse is coded with a non-symmetric pattern :

Also, and this might seem silly, but are you sure the encoder is exactly the same reference? I think avago has a lot of different reference with the same form factor… We are using the AEDT-9810-Z00

Keep us posted, I would love to see how Moteus performs with odri motors.

Best, T.

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I ordered the kit as per github instructions, but I have confirmed that it’s the correct way up. There is really nothing I can see wrong with the setup which is why I am particularly frustrated regarding this signal haha. And yep, that’s the exact part number I ordered to. Thank you for being thorough though :wink:

As for Moteus, I had to change the firmware to accept Index signal as an interrupt rather than its default sampling rate, as that was too slow and usually missed the signal. Otherwise works great.

Oh, Moteus is 3v3 so I have to run the signals through a level shifter in addition to normal wiring. Again, most of my actuators perform wonderfully without issue, so this is not the issue as far as I am aware.