XS_EUPXS(XS_TellStick_tdSensor); /* prototype to pass -Wmissing-prototypes */
XS_EUPXS(XS_TellStick_tdSensor)
{
  dVAR; dXSARGS;
  if (items != 6)
    croak_xs_usage(cv,  "protocol, protocolLen, model, modelLen, id, dataTypes");
  {
    char *  protocol = (char *)SvPV_nolen(ST(0))
;
    int     protocolLen = (int)SvIV(ST(1))
;
    char *  model = (char *)SvPV_nolen(ST(2))
;
    int     modelLen = (int)SvIV(ST(3))
;
    int     id = (int)SvIV(ST(4))
;
    int     dataTypes = (int)SvIV(ST(5))
;
    int     RETVAL;
    dXSTARG;

    printf("id1: %d\n", id);
    RETVAL = tdSensor(protocol, protocolLen, model, modelLen, &id, &dataTypes);
    printf("id2: %d\n", id);
    XSprePUSH; PUSHi((IV)RETVAL);
  }
  XSRETURN(1);
}


##</code><code>##

...
my $sensorId = 1;
TellStick::tdSensor($protocol, 25, $model, 25, $sensorId, $dataTypes);
 print "protocol: $protocol, model: $model, sensorId: $sensorId, dataTypes: $dataTypes\n";

I get the output

id1: 1
id2: 51
protocol: mandolyn, model: temperaturehumidity, sensorId: 1, dataTypes: 2