RP2 stepper motor controller using PIO and DMA

[bikeNomad]

I've just published an improved and extended version of @fmafma 's stepper motor control code here: https://github.com/bikeNomad/micropython-rp2-smartStepper

A MicroPython library for smooth, non-blocking stepper motor control on the
Raspberry Pi Pico (RP2040) and Pico2 (RP2350). Uses PIO state machines and DMA for precise,
CPU-independent pulse generation and position counting.

Features

• Non-blocking absolute and relative moves (moveTo)
• Non-blocking continuous jog (jog) with configurable speed
• Async homing with configurable sensor polarity; handles pre-asserted sensor (homing.py)
• Smooth acceleration and deceleration (linear, smooth1, smooth2/smootherstep, sine curves)
• Graceful stop with deceleration, or emergency hard stop
• Dynamic parameter adjustment (speed, acceleration) mid-move with automatic motion replan
• Position tracking via PIO pulse counter
• Active-low enable pin support (auto-enabled on move start)
• Move timeout with automatic emergency stop
• Up to 4 simultaneous stepper instances (limited by RP2040 PIO state machines)
• mip installable
• Hardware-in-the-loop tests using Saleae Logic analyzer

I think it should be possible to have more stepper instances (especially on the RP2350) but I haven't worked out how to do that yet, as each instance takes one SM for pulse generation and one for pulse counting.

[fmafma]

That's great! Thanks for sharing.
I'll link your project on mine, and update my codes ;o)

[bikeNomad]

I just added multi-axis synchronized motion, for anyone who wants to do CNC stuff...

[mattytrentini]

This looks fantastic @bikeNomad! Can you recommend any readily available hardware that would be a good match for the library?

[bikeNomad]

As @fmafma says, this is step/direction, so the more primitive drivers that require per-phase outputs won't work.

But there's lots of drivers that take step/direction inputs (like the DRV8825). Pololu has a lot of these (as well as motors): https://www.pololu.com/category/120/stepper-motor-drivers

The choice also depends on how much power/torque you need. Larger motors often offer step/direction interfaces directly (and also often have closed-loop control). Here's a good example: https://www.amazon.com/CNCTOPBAOS-Integrated-Multi-Microstep-Industrial-Automated/dp/B0DZBBFF4D/ref=sr_1_4

And typically you'll also want some way to sense the home position. Make sure that there's some distance between the home position and the hard limit; you'll want the home switch/sensor to assert for the entire distance between home and the hard stop so the motor can decelerate.

[fmafma]

Le jeudi 05 mars 2026, Matt a écrit :

This looks fantastic @bikeNomad!

+1, great job, again!

Can you recommend any readily available hardware that would be a good match for the library?

You can use any driver with step/dir interface. If you need several axis, you could use the famous Arduino CNC shield: https://www.amazon.com/s?k=cnc%20shield and a board like this: https://www.cnx-software.com/2023/08/09/raspberry-pi-pico-to-arduino-uno-adapter-relies-on-flexypins-for-castellated-holes https://fr.aliexpress.com/item/1005007406849003.html https://www.hackster.io/news/picuno-rp2040-in-the-arduino-uno-form-factor-56e568c494da https://microfan.shop/products/rp2040-uno-r2 https://www.amazon.com/APTINEX-Lakduino-RP2040-Development-Board/dp/B0D73KTY7J (I built my own).

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-- Frédéric

[bikeNomad]

I just added arc motion as well.

[fmafma]

Le vendredi 06 mars 2026, Ned a écrit :

I just added arc motion as well.

Awesome! Just add a path planner, and we have a full CNC/3D printing firmware ;o)

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-- Frédéric