ch32v003-ext-board/README.md

CH32-16-CH-EXT

A simple CH32V003-based extension board providing 16 outputs (2x 74HC595), primarily designed for controlling Chinese 16-relay modules (archive) over RS485. Uses 64-byte internal flash page for state persistence.

KiCad hardware design files are in the hw directory.

comm protocol

uses Modbus RTU protocol over RS485

Config

Baud Rate: 9600
Data Bits: 8
Stop Bits: 1
Parity: None

Modbus

• Function Code: 0x06 (Write Single Register)
• Default Slave Address: 0x01
• Register Map:
  • Register 0x0000: Output Control Register (16 bits for controlling 16 relays)

Outputs

Each bit in the control register corresponds to one output:

• Bit 0 controls Output 1
• Bit 1 controls Output 2
• etc.

Msg

Byte 0: Slave Address (0x01)
Byte 1: Function Code (0x06)
Byte 2: Register Address High (0x00)
Byte 3: Register Address Low (0x00)
Byte 4: Data High Byte
Byte 5: Data Low Byte
Byte 6: CRC Low Byte
Byte 7: CRC High Byte