CH32V003 MODBUS default: UART TX(C0) RX(C1) baud:9600 input digital: x1(D5) output Digital: y1(D6) reference https://www.modbustools.com/modbus.html https://crccalc.com/?crc=123456789&method=CRC-16/MODBUS&datatype=hex&outtype=0