Polling serial port

1

I have a number of sensors that send data to the serial port, some every second and some 10 times a second.

Right now I have my ports defined like:

String Outside_Air_Sensor {serial="/dev/ttyPort0@9600,BASE64"}

And rules that kick off when sensor receives update such as:

rule "Outside_Air_Sensor"
when
  Item Outside_Air_Sensor received update
then
  val to64 = DatatypeConverter::parseBase64Binary(Outside_Air_Sensor.state.toString)
  val ByteBuffer bb = ByteBuffer::wrap(to64)
  val short start = bb.getShort
  val short length = bb.getShort
  if (start==16973 && length==28) {
    val short pm1 = bb.getShort
    if (pm1>0) {
      postUpdate(Outside_PM1, pm1.toString)
    }
    val short pm25 = bb.getShort
    if (pm25>0) {
      postUpdate(Outside_PM25, pm25.toString)
    }
    val short pm10 = bb.getShort
    if (pm10>0) {
      postUpdate(Outside_PM10, pm10.toString)
    }
  }
end

Things basically work, but I don’t need to know the air quality every second, or the level of my septic tank 10 times a second. Is there a way to write a rule that opens the serial port, based on cron say every 30 seconds, reads one value from the serial port and then closes it?

2

Have you considered rules that trigger on change, rather than update?

I do not think there is a way to poll an incoming stream. These are rather oddly behaved devices, many transmitting onto a serial bus, I wonder how they manage collisions.

Anyway, you may be able to achieve a serial port on-off effect using the Config Admin binding


I’ve no experience with it, but it should allow redirection to a non-existant port (as a substitute for port off) from a rule.
You should expect overrun errors from the unserviced working port.
Quite how you recover from that, or deal with an error when you switch back in the middle of a transmission, I’m not sure.