5i25 + 7i85s +....

Btw. i know i talk to an verry experienced goat.
I just need to see it to get a feeling for everything that happens.

If it does not reach the commanded position in local stepgen feedback mode,
there's some kind of LinuxCNC setup error.

If it does not reach the commanded position in encoder closed loop mode,
it could be either LinuxCNC tuning issues, motor drive tuning issues or both

The PID stepgen is a nearly perfect first order control loop so has nearly ideal step generation capabilities
This is because:

1. The rate settability is 32 bits (well somewhat lower because the top bits are typically not used)
2. The rate is updated 1000 or more times a second based on fine position feedback
3. There is very little delay between reading the current position and updating the velocity to intersect the next waypoint
( This delay can be compensated for if desired with FF2 )

Note that a encoder feedback system will show _much_ larger errors since
there are significant following errors in the drive/motor/load

Hi Andy,

I have a similar situation so I just jumped in on this thread.

Been wiring the 6i25+7i85S boards for an XYZ mill project but can't seem to make it work. We're still using a Universal PWM from Pico.

I used only XYZ PWM, DIR and XYZ A, B & I encoder signals. That leaves me extra I/Os.

I flashed the boards using the 5i25_7i85SPX2.bit.

This caught my eye: "Note that there are 17 perfectly usable 5V TTL GPIO pins on the second header of the 5i25, though."

Are you referring to the I/O connector 2 on PNCCONF, the same as this 2nd header of 5i25/6i25? And the I/O connector 3 (on PNCCONF), the 25-pin going to the 7i85S?

Hope you can clear this out for me. Thanks. Nuki.

I don't know what the connector is called in PnCConf.
You might need to disable some functions (stepgens etc) depending on firmware to make those pins available as GPIO