ShiboSoftwareDev/nema8-20mm-pd-mini-controller

README.md

# NEMA 8 20 mm USB-C PD TMC2209 controller

Compact four-layer tscircuit controller for the StepperOnline
[8HS15-0604S](https://www.omc-stepperonline.com/nema-8-bipolar-1-8deg-4ncm-5-7oz-in-0-6a-6v-20x20x38mm-4-wires-8hs15-0604s)
bipolar stepper motor. This is a separate 20 mm × 20 mm design intended to mount on
the motor with two M2 screws and insulating spacers.

## Target motor and mechanics

- NEMA 8, 20 mm square body, 1.8 degree step angle
- 4 Ncm holding torque, 0.60 A/phase, 6 V
- 11 ohm and 5.5 mH ±20% per phase at 1 kHz
- 20 mm × 20 mm, four layers, 1.6 mm FR-4
- Two diagonal 2.2 mm mounting holes on the motor's 15.4 mm M2 pattern
- Components are fitted on both sides; use spacers tall enough to clear bottom-side parts
- `J_MOTOR`: pin 1 B− blue, pin 2 B+ red, pin 3 A+ black, pin 4 A− green

## Electrical architecture

- One power-only USB-C input with CH224K fixed to request 9 V USB PD
- TMC2209-LA-T with STEP/DIR, single-wire UART, StallGuard, and StealthChop
- External bottom-edge pads for GND, VIO, STEP, DIR, UART, and ENN
- No onboard MCU: an external controller and VIO supply are mandatory
- 1.1 A resettable fuse, reverse-polarity diode, SMAJ12A transient clamp, 10 uF
  local bulk capacitance, and high-frequency decoupling
- Two 0.33 ohm, 1%, 0.5 W current-sense resistors
- Fixed 10 kohm / 10 kohm current-reference divider
- 3 × 3 exposed-pad/thermal-via field under the driver

The earlier selectable 5 V motor-supply mode is deliberately absent: the TMC2209's
internal regulator requires at least 5.5 V. A non-PD source may leave the connector at
5 V, so confirm VM before enabling the driver. The TVS and local capacitance mitigate
regeneration overshoot but are not an active energy sink; VM must still be measured
during worst-case deceleration.

## PCB routing constraints

- Default tscircuit autorouter
- All vias request 0.30 mm drills and 0.45 mm outer diameters
- Motor-phase and supply buses request wide traces; sense buses request separate routing
- Minimum configured copper-to-board-edge clearance is 0.17 mm
- The two-sided assembly remains screw-mountable when insulating spacers provide enough
  clearance above the motor face

### Important routing limitation

The installed tscircuit release does not serialize the requested allowed-layer metadata
for source buses. The generated artifact therefore contains some motor and supply-route
segments on inner layers, although the sense routes remain on top/bottom copper. This
must be fixed in a router/tool version that honors the layer constraint, or explicitly
accepted by the electrical reviewer, before the board is sent to fabrication.

## JLCPCB/LCSC sourcing

Every fitted electrical component has an LCSC/JLCPCB catalog identifier in the source.
Key parts include:

| Function | Part | LCSC |
| --- | --- | --- |
| Motor driver | TMC2209-LA-T | C2150710 |
| PD controller | CH224K | C970725 |
| USB-C connector | TYPE-C-31-M-12 | C165948 |
| Resettable fuse | BSMD1206-110-16V | C2803346 |
| Reverse diode | PMEG6020ELRX | C478000 |
| 12 V TVS diode | SMAJ12A | C113957 |
| 0.33 ohm sense resistors | PT1206FR-7W0R33L | C858786 |
| Motor connector | BM04B-SRSS-TB(LF)(SN) | C160390 |

Catalog identifiers do not guarantee live stock. Recheck availability immediately before
ordering and manually confirm JLCPCB pick-and-place rotations and pin-1 orientation.

## Automated verification

The checked source is `index.circuit.tsx`.

```sh
tsci build
tsci check index.circuit.tsx
tsci check shorts dist/index/circuit.json --mode pcb --layer all
tsci check shorts index.circuit.tsx --mode gerber --layer all
tsci check netlist index.circuit.tsx
tsci check placement index.circuit.tsx
tsci check source index.circuit.tsx
tsci check pin_specification index.circuit.tsx
```

Results: zero build/DRC errors, zero PCB shorts, zero Gerber shorts, zero netlist errors,
zero placement-check errors, and zero source-check errors. The generic aggregate check
has 40 warnings and the pin-specification check has 11 metadata warnings. The raw build
also reports a small `U_PD` / `R_PD_SENSE` overlap even though the dedicated placement
check reports zero issues; inspect that region visually before fabrication.

## Reviewer sign-off still required

- Resolve or accept the inner-layer motor/supply segments described above
- Inspect the reported `U_PD` / `R_PD_SENSE` overlap
- Confirm the 0.17 mm edge-clearance rule is accepted by the selected fab process
- Verify every JLCPCB PnP rotation, pin-1 mark, footprint, and current stock level
- Validate 9 V PD negotiation and safe behavior when only 5 V fallback is available
- Measure phase current, driver temperature, VM ringing, and regeneration overshoot on hardware
- Confirm the selected spacer height clears all bottom-side components and solder joints

## Primary references

- [TMC2209 product page and datasheet](https://www.analog.com/en/products/TMC2209.html)
- [StepperOnline 8HS15-0604S product page](https://www.omc-stepperonline.com/nema-8-bipolar-1-8deg-4ncm-5-7oz-in-0-6a-6v-20x20x38mm-4-wires-8hs15-0604s)