MODBUS_READ_REGISTER(3) Libmodbus Manual MODBUS_READ_REGISTER(3)
NAME
modbus_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
", modbus_strerror(errno));
modbus_free(ctx);
return -1;
}
rc = modbus_read_registers(ctx, 0, 10, tab_reg);
if (rc == -1) {
fprintf(stderr, "%s
", modbus_strerror(errno));
return -1;
}
for (i=0; i < rc; i++) {
printf("reg[%d]=%d (0x%X)
", i, tab_reg[i], tab_reg[i]);
}
modbus_close(ctx);
modbus_free(ctx);
SEE ALSO
modbus_write_register(3) modbus_write_registers(3)
AUTHORS
The libmodbus documentation was written by Stephane Raimbault <stephane.raimbault@gmail.com[1]>
NOTES
1. stephane.raimbault@gmail.com
mailto:stephane.raimbault@gmail.com
libmodbus 3.0.3 05/26/2012 MODBUS_READ_REGISTER(3)
