Accesible Motion with Steppers

Big update! The stepper controller firmware has reached a stable, working state — and I’m happy to report that all major features are now live and tested!

✅ Core Features Now Working

Here’s what’s running smoothly:

• CW (Clockwise) Mode – Tap the encoder, and the motor rotates smoothly in one direction.

• CCW (Counter-Clockwise) Mode – Same deal, but in reverse!

• ARC Mode – The star feature. Users define the left and right limits using the Auxillary buttons. Once saved, the motor oscillates smoothly between the two ends.

• Play/Pause – Pressing the encoder switch now pauses or resumes the motion, regardless of mode. Super intuitive.

• Non-Volatile Memory – The system now remembers the last mode and positions even after power-off. This makes it ideal for installations or embedded setups — set it once and forget it.

🧠 How It Works for the User

1. Choose your mode (CW, CCW, ARC) while the motor is paused.

2. In ARC mode, press the Aux buttons and rotate to set endpoints, then press the Save/Erase Button to save the position. 

3. Press the play button to start motion.

4. Pause or play any time with a single click.

5. Power it off and on — your config is still there!

🧪 What’s Next?

• Implement I2C daisy-chaining for multiple synchronized motors.

• Create a printable case or mounting bracket.

• Start testing with real-world mechanical linkages and kinetic art setups.

🎊 This is a huge step forward in making stepper motor control plug-and-play for non-engineers. No code, no libraries — just intuitive hardware and motion.

More to come soon!

The PCBs finally arrived from Lioncircuits, and I kicked off the initial hardware bring-up!

Assembly Progress

• The USB-C port footprint didn’t align with the mounting holes — a mechanical mismatch. This means the USB port won't be populated in this revision.

• I began with soldering SMD resistors:

  • 1kΩ for LEDs

  • 10kΩ pull-ups for I2C (SDA & SCL)

• Next came the A03416 MOSFETs, followed by a careful hand-solder of the CH32V003 microcontroller.
  
  

• To test programming, I added a simple pin header breakout for 5V, GND, and SWIO, which worked flawlessly.

• Finished off with all through-hole parts: switches, LEDs, the rotary encoder, and the stepper motor connector.

All components passed individual tests — switches and LEDs functioned correctly.

Debugging the Stepper Motor

I encountered a strange issue — the stepper motor wouldn’t move.

To isolate the problem, I connected an LED in place of the motor to observe the pin sequences. Strangely, the LED connected to PD7 wasn’t toggling. I checked the MOSFET for shorts — no issues there.

After digging into the datasheet, I realized the root cause:
PD7 is also the NRST (reset) pin, which is pulled high at startup, unintentionally turning the MOSFET on and grounding the connected pin. 

Solution?

I used the WCH-Link Utility to reconfigure PD7 as a general I/O pin. Once that was done, the sequence worked — and the stepper motor spun beautifully.

⚡ Power Concerns

While testing the motor, I noticed the power LED dims significantly when the stepper coil energizes. Measuring current draw showed around 200mA, which is expected.

The issue appears to be a voltage dip when coils energize. I’ve switched to an external power supply for now, but will be adding a beefy capacitor across 5V and GND to buffer the current surges and stabilize power delivery.

🧪 What’s Next?

• Fix the USB-C footprint in the next revision

• Tune power filtering with appropriate capacitance

• Begin firmware work for motion configuration and I2C chaining

• Build mounting brackets and start integration with real-world mechanisms

More to come — but for now, I’m thrilled the first spin of the motor is live!