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!