Name

modbus_rtu_get_serial_mode - get the current serial mode

Synopsis

int modbus_rtu_get_serial_mode(modbus_t *ctx);

Description

The modbus_rtu_get_serial_mode() function shall return the serial mode currently used by the libmodbus context:

MODBUS_RTU_RS232, the serial line is set for RS232 communication. RS-232 (Recommended Standard 232) is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports
MODBUS_RTU_RS485, the serial line is set for RS485 communication. EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems. This standard is widely used for communications in industrial automation because it can be used effectively over long distances and in electrically noisy environments. This function is only available on Linux kernels 2.6.28 onwards and can only be used with a context using a RTU backend.

Return value

The function shall return MODBUS_RTU_RS232 or MODBUS_RTU_RS485 if successful. Otherwise it shall return -1 and set errno to one of the values defined below.

Errors

•: EINVAL, the current libmodbus backend is not RTU.