R4IOI16 technical support

Hello,

I bought your R4IOI16 module in the 8DI-8DO version:

R4IOI16_8DI-8DO
16DI/16DO/8DI-8DO/4DI-12DO/12DI-4DO Modbus RTU Digital IO RS485 2.54mm Pin Core Board

I am trying to use it with an ESP32-S3 via RS485 Modbus RTU, but I cannot get a valid Modbus response.

My current setup:

- Module version: 8DI-8DO
- Jumper/resistor position: M2 = 8DI-8DO
- Power supply: 5.06V connected to 5V and G
- VIN is not connected
- G and GND have continuity on the module
- RS485 wiring:
- ESP32 RS485_A to module A+
- ESP32 RS485_B to module B-
- common GND connected
- Baudrate tested: 9600
- Format tested: 8N1
- Slave address tested: 1
- I also tried swapping A+ and B-
- I also tried factory reset by connecting RES to GND for 5 seconds and power cycling the module

I tested the following Modbus requests with correct CRC, but received no valid response:

- Read coils: slave 1, function 01, address 0x0000, quantity 8
- Read discrete inputs: slave 1, function 02, address 0x0000, quantity 8
- Read holding register: slave 1, function 03, address 0x0000, quantity 1
- Read holding register: slave 1, function 03, address 0x00F5, quantity 1
- Read holding register: slave 1, function 03, address 0x00F6, quantity 1

Could you please send me the complete R4IOI16 Modbus RTU command document?

I need the following information:

1. Default slave address
2. Default baudrate, parity, stop bits
3. Complete register map
4. Coil addresses for outputs
5. Input addresses for digital inputs
6. Holding register addresses for configuration
7. Correct commands/examples for:
- reading digital inputs in 8DI-8DO mode
- reading digital output states
- switching one output ON/OFF
- changing slave address
- changing baudrate/parity
- factory reset
8. Whether A+ / B- labeling follows standard RS485 polarity or needs to be swapped for typical RS485 adapters
9. Whether the module should answer immediately after power-up without additional configuration

Please also confirm whether the following request should work after factory reset:

01 02 00 00 00 08 79 CC

Thank you.

Eletechsup:

This requires debugging.
1 Please use a USB-to-RS485 adapter on your computer to debug the R4IOI16_8DI-8DO.
2 Use the USB-to-RS485 adapter to monitor the data sent by the ESP32-S3 and verify that the commands are correct.
3 Finally, use the ESP32-S3 to control the R4IOI16_8DI-8DO.