rigol_ds1xx2_send_data(devc->fd, ":CHAN1:OFFS?\n");
len = read(devc->fd, buf, sizeof(buf));
buf[len] = 0;
devc->offset = atof(buf);
rigol_ds1xx2_send_data(devc->fd, ":CHAN1:OFFS?\n");
len = read(devc->fd, buf, sizeof(buf));
buf[len] = 0;
devc->offset = atof(buf);