modbus_read_registers
Name
modbus_read_registers - read many registers
Synopsis
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 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", 502);
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);