No tx/rx pin definitions, no rx enable definition, no buffer size. Its best to let the driver define the buffer size. Normally you would only have one enable pin: MODBUS_SERIAL_ENABLE_PIN and define that as the pin you are using. You only need to define them if your configuration is different. These three are defined in the driver, modbus.c. Even if your hardware has two pins on its interface IC, for Modbus, connect them together and drive them as a single pin. Defining both to be the same pin may cause a clash, possibly preventing receiving data. Unless you have two enable pins and are using full duplex (Modbus is half-duplex), don't define both. So, the pin definitions won't do anything and are be confusing: so delete them. Your interrupt source definition forces the modbus driver to use hardware UART1. The serial pin definitions are only needed if you are NOT using a hardware UART. I saw the ex_modbus_slave.c but I can't do.

I am using the version CCS 5.015 and I read the library, it had to define MODBUS_SLAVE_ADDRESS, didn't use MODBUS_ADDRESS as previous version. I used it to send and receive data to computer by using Hercule. The CCS modbus driver does not use MODBUS_SLAVE_ADDRESS. Note that this doesn't set 'MODBUS_SLAVE_ADDRESS'. Then what you are doing is basically the same as the example (ex_modbus_slave.c). Modbus_kbhit won't ever go true unless data is being received. That the signal here is idling high, and going low?. Have you actually verified with a scope that there is serial data arriving at the RX pin?. Modbus poll only had a status 'Timeout error'. I connected PIN C3 to Led to debug, my code stuck at 'if(modbus_kbhit())', I replace it by code 'while(!modbus_kbhit()) ' but it still did not run. Modbus_diagnostics_rsp(MODBUS_SLAVE_ADDRESS,modbus_rx.func,data) #define MODBUS_SERIAL_RX_ENABLE PIN_C5 // Controls RE pin for RS485 #define MODBUS_SERIAL_ENABLE_PIN PIN_C5 // Controls DE pin for RS485 #define MODBUS_SERIAL_RX_PIN PIN_C7 // Data receive pin #define MODBUS_SERIAL_TX_PIN PIN_C6 // Data transmit pin #define MODBUS_SERIAL_TYPE MODBUS_RTU //use MODBUS_ASCII for ASCII mode #define MODBUS_SERIAL_INT_SOURCE MODBUS_INT_RDA #define MODBUS_PROTOCOL MODBUS_PROTOCOL_SERIAL I tried to send data from pic to computer using modbus RTU, I used modbus poll and I can't receive anything.

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Ccs c modbus rtu