How To : store bytes in an int array by USB Serial

Setup, Configuration and Use Beginners
1

*** Platform information:**

  • Hardware: Raspberry Pi 2 B+ and Arduino Mega2560
  • openHAB version: openHAB2

*** Issue of the topic: please be detailed explaining your issue**
Hello. I’m newbies.
I use Arduino and Raspberry. And I connected by serial communication(ttyUSB0).
Arduino sends several bytes of data. like this 90 165 1 1 0 1 …
(there is no space, “;” and “,”)
I want to store bytes in an int array. and i want to check the saved value.
I saw “header1 match”, but not “header2 match”
I did a search last week. But i could not find the answer.
Please help me T.T

*** Please post configurations (if applicable):**

  • Items configuration related to the issue

     String  TestLogData         "Log Data [%s]"    {serial="/dev/ttyUSB0@9600"}

  • Rules code related to the issue

     rule "Received Log Data"
 when
         Item TestLogData received update
 then

         var List<Integer> LogData = TestLogData.state.toString.getBytes()
         var Number header1
         var Number header2

         header1 = LogData.get(0)
         header2 = LogData.get(1)

         if (header1 == 0x5A)
         {
                logInfo("Debug", "header1 match")
         }

         if (header2 == 0xA5)
         {
                logInfo("Debug", "header2 match")
         }

  • If logs where generated please post these here using code fences:

2

What exactly does is the serial string?

In your example, there IS a space.

Do this:

rule "Received Log Data"
when
    Item TestLogData received update
then
    var List<Integer> LogData = TestLogData.state.toString.getBytes()
    var Number header1
    var Number header2

    logInfo("TestLogData", TestLogData.toString)
    header1 = LogData.get(0)
    header2 = LogData.get(1)

    if (header1 == 0x5A) {
        logInfo("Debug", "header1 match")
    }

    if (header2 == 0xA5) {
        logInfo("Debug", "header2 match")
    }
end

I added a logInfo to print the whole string
What does the log show when you receive data?

3

Thank you for your help.
I wanted to make the example look good.

Serial1
Serial1.JPG1401×272 33.8 KB

Arduino send serial data.
0x5A 0xA5 …

But Log data something wrong…t.t

Log
Log.JPG1093×30 8.36 KB

What did I do wrong?

4

Only the first byte is recognised properly, have you checked that your receiving serial port is configured properly especially the parity and end bits?

5

Could you tell me how to check?
I just checked “console=serial0, 9600” in “cmdline.txt” file.

and when i change the code
TestLogData.state.toString.getBytes()
-> TestLogData.state.toString.getBytes(“ASCII”)
Log1

only the second data is abnormal. 165 is displayed as 63.
so i think…are they displayed as different values beyond 128??

what do you think???

6

Beyond 128 it could be that you byte is interpreted as a negative number.
It’s a very long time ago I have done this kind for bit crunching

1 Like
7

Negative numbers are to be expected when handling bytes > 128
Old post which maybe has relevant handling methods