MODBUS_READ_REGISTER(3) Libmodbus Manual MODBUS_READ_REGISTER(3)NAMEmodbus_read_registers - read many registers
SYNOPSIS
int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t
*dest);
DESCRIPTION
The modbus_read_registers() function shall read the content of the nb
holding registers to the address 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 0x03 (read holding
registers).
RETURN VALUE
The modbus_read_registers() function shall return the number of read
registers if successful. Otherwise it shall return -1 and set errno.
ERRORS
EMBMDATA
Too many registers requested
EXAMPLE
modbus_t *ctx;
uint16_t tab_reg[64];
int rc;
int i;
ctx = modbus_new_tcp("127.0.0.1", 1502);
if (modbus_connect(ctx) == -1) {
fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
modbus_free(ctx);
return -1;
}
rc = modbus_read_registers(ctx, 0, 10, tab_reg);
if (rc == -1) {
fprintf(stderr, "%s\n", modbus_strerror(errno));
return -1;
}
for (i=0; i < rc; i++) {
printf("reg[%d]=%d (0x%X)\n", i, tab_reg[i], tab_reg[i]);
}
modbus_close(ctx);
modbus_free(ctx);
SEE ALSOmodbus_write_register(3)modbus_write_registers(3)AUTHORS
The libmodbus documentation was written by Stéphane Raimbault
<stephane.raimbault@gmail.com[1]>
NOTES
1. stephane.raimbault@gmail.com
mailto:stephane.raimbault@gmail.com
libmodbus 3.1.0 10/06/2013 MODBUS_READ_REGISTER(3)