def _st_decode(self, msg):
        """ST: Temperature update."""
        group = int(msg[4:5])
        temperature = int(msg[7:10])
        if group == 0:
            temperature -= 60
        elif group == 1:
            temperature -= 40
        return {'group': group, 'device': int(msg[5:7])-1,
                'temperature': temperature}