# RS232 gateway

## Sending an RS232 message

Simply publish the message you wish to transmit, minus the prefix and postfix. For example, to send the "Turn On" signal for a Mitsubishi XD221U projector, the code is simply '!' so you would use the command

`mosquitto_pub -t home/OpenMQTTGateway/commands/MQTTtoRS232 -m  '{"value": "!"}'`

It will automatically add the prefix and postfix you set in [config_RS232.h](https://github.com/1technophile/OpenMQTTGateway/blob/master/main/config_RS232.h).

## Receiving an RS232 message
To receive a message, subscribe to all with `mosquitto_sub -t +/# -v`
and perform an action that should get a response from the device. For example, If I were to send the "Turn On" signal from earlier, I would receive back

```json
home/OpenMQTTGateway/RS232toMQTT {"value":"1"}
```

Because this projector echoes back a received command to acknowledge. Some devices will send a NACK, or Negative Acknowledge, to confirm that they received your message but could not comply. That would look like

```json
home/OpenMQTTGateway/RStoMQTT {"value":"!:N"}
```