dowjames v5.1¶
This is split-flap module PCB designed by dowjames. It integrates the PCF8575 I/O expander, ULN2003 motor driver, hall sensor connector, and I²C daisy-chain headers onto a single compact board — ordered fully assembled from JLCPCB.
Specs¶
| I²C expander | PCF8575 |
| Motor driver | ULN2003 |
| Address config | 3-pin DIP switch (A0/A1/A2) — 8 unique addresses |
| Daisy-chain | 4-pin NEXT/PREV right-angle headers (+5V, GND, SCL, SDA) |
| Assembly | Top-side SMT, assembled by JLCPCB |
| Minimum order | 10 boards |
What arrives assembled¶
All SMT components are pre-soldered by JLCPCB:
- PCF8575 I²C I/O expander
- ULN2003 motor driver
- Bypass capacitors
- DIP switch
- Hall sensor connector
- NEXT/PREV daisy-chain headers
What you still need to do¶
Common gotchas for all custom PCBs
Before proceeding, read the common gotchas on the Custom PCBs page — firmware flashing order, pull-up resistors, and power wiring apply to this board.
1. Add I²C Pull-Up Resistors¶
Add 4.7kΩ pull-up resistors on the first board in each chain only — one resistor from SDA to +5V, one from SCL to +5V.
2. Set DIP Switch Addresses¶
Each board needs a unique I²C address set via the onboard 3-pin DIP switch. See the I²C reference for the address table. Every module in a chain must have a different setting.