modbus_write_and_read_registers - write and read many registers in a single transaction
int modbus_write_and_read_registers(
modbus_t *ctx,
int write_addr, int write_nb, const uint16_t *src,
int read_addr, int read_nb, const uint16_t *dest
);
The modbus_write_and_read_registers() function shall write the content of the
write_nb
holding registers from the array 'src' to the address write_addr
of
the remote device then shall read the content of the read_nb
holding registers
to the address read_addr
of the remote device. The result of reading is stored
in dest
array as word values (16 bits).
You must take care to allocate enough memory to store the results in dest
(at least nb
* sizeof(uint16_t)).
The function uses the Modbus function code 0x17 (write/read registers).
The function shall return the number of read registers if successful. Otherwise it shall return -1 and set errno.