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modbus_read_input_bits

Name

modbus_read_input_bits - read many input bits

Synopsis

int modbus_read_input_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);

Description

The modbus_read_input_bits() function shall read the content of the nb input bits to the address addr of the remote device. The result of reading is stored in dest array as unsigned bytes (8 bits) set to TRUE or FALSE.

The dest array must be allocated with at least nb * sizeof(uint8_t) bytes. It is the caller's responsibility to ensure the buffer is large enough to hold all the bits to be read.

The function uses the Modbus function code 0x02 (read input status).

Return value

The function shall return the number of read input status if successful. Otherwise it shall return -1 and set errno.

Errors

  • EINVAL, the ctx or dest argument is NULL, or nb is less than 1.
  • EMBMDATA, too many discrete inputs requested (nb > MODBUS_MAX_READ_BITS).

See also