filter SSerialReceived to reduce traffic

[torowi]

Hey everyone, I have connected a device via serial connection and I receive successfully MQTT-Messages.
The problem is now that it sends many unnecessary messages, sometimes several times per second and I would like to reduce that.

Is there a way to send only messages which begin with "FC16"?

Example values...

MQT: tele/tasmota_C85D08/RESULT = {"SSerialReceived":"0F220400417175612020202020202020202020204175746F20202054534120203432B04349"}
MQT: tele/tasmota_C85D08/RESULT = {"SSerialReceived":"FC160B0101A5017800D2DEC8000002000206162223040000E2"}
MQT: tele/tasmota_C85D08/RESULT = {"SSerialReceived":"0F220400417175612020202020202020202020204175746F20202054534120203432B04349"}

Thanks in advance!

[sfromis]

First, I'd suggest to stop worrying about a small amount of "unnecessary" messages without real "cost".

Still, using SetOption147, you could disable the automatic publish, and then use features like rules or Berry to pick up on the ones you want, and process them, including doing your own publish.

[torowi]

scripting sounds good, so its maybe possible to decode some of the hex values to push the in readable format.
But I'm nor familiar with berry...

So I looked for rules, but I cant figure out how to say "starts with "FC 16""
Do you have a hint for me?

[sfromis]

No such processing capabilities with rules, but great option with Berry.

[torowi]

does a rule then call the berry script or how does it work?

[sfromis]

No, with Berry you have tasmota.add_rule with same trigger format (but otherwise not related to "classic" rules).

With hex data, one strategy could be to create a bytes object with the content, and then you have a number of methods to extract data (like numbers) from the blob.

And the mqtt module can unsurprisingly be used for things like publish

[torowi]

So, I gave berry a try. I first had some issues to get full messages, so I played around with delays, not really knowing what I was doing...
But now I struggle to extract some values...

block = bytes('FC160B0101CF01BD01E6DEC800000200020D20292404000045')

so with var b4 = block[4] I get 1. I tried with var hex_46 = format(b4, "02X") but this gives nil....

Rest of code...

class SerialTest
  var ser, collected, collecttime

  def init()
    self.ser = serial(8, -1, 9600, serial.SERIAL_8N1)
    self.collected = []
    self.collecttime = tasmota.millis()
    tasmota.set_timer(0, /->self.loop())
  end

  def loop()
    self.serialpoll()
    tasmota.set_timer(50, /->self.loop())
  end

  def serialpoll()
    while self.ser.available() > 0
      tasmota.delay(50)
      var block = self.ser.read()
      if block.size() > 0 && block[0] == 0xFC
        print(block)
        self.process(block)
      end
    end
  end

  def process(block)
    var b4 = block[4]
    var hex_b4 = format(b4, "02X") 

    print("B4: ",hex_b4)
  end
end

var test = SerialTest()

[sfromis]

As illustrated by the docs about the format function, you need the usual notation with % to indicate where you have a formatting specification, which could be embedded in a longer text.

You could also use f-strings like print(f'B4: {b4:02X}')
(As the formatting part of f-strings is wrapped in {}, no % as part of this notation.

BTW. When it comes to getting full messages, the more robust approach would be to be able to determine it by message content, but that obviously depends on the format and protocol. This would imply collecting data in a buffer until you have enough. In general, it is preferable to not rely on using tasmota.delay(), as this is completely blocking to Tasmota operation, especially when you do it in a function called in 50 ms ticks, lowering your polling rate.

In case there would be a risk of your serialpoll() method getting a lot of data, and not exiting per message, it would be possible for your code to block Tasmota to the point of crashing. Not saying that this is "very likely", just as a consideration for robust coding.

Another approach to the polling could be to add your instance as a driver, and use callbacks like every_50ms(), but no problem using the tasmota.set_timer approach.