modbus_rtu_set_custom_rts - Man Page

set a function to be used for custom RTS implementation


int modbus_rtu_set_custom_rts(modbus_t *ctx, void (set_rts) (modbus_t ctx, int on))


The modbus_rtu_set_custom_rts() function shall set a custom function to be called when the RTS pin is to be set before and after a transmission. By default this is set to an internal function that toggles the RTS pin using an ioctl call.

Note that this function adheres to the RTS mode, the values MODBUS_RTU_RTS_UP or MODBUS_RTU_RTS_DOWN must be used for the function to be called.

This function can only be used with a context using a RTU backend.

Return Value

The modbus_rtu_set_custom_rts() function shall return 0 if successful. Otherwise it shall return -1 and set errno to one of the values defined below.



The libmodbus backend is not RTU.


Jimmy Bergström <>

The libmodbus documentation was written by Stéphane Raimbault <>

Referenced By


01/25/2024 libmodbus v3.1.7 libmodbus Manual