B4J Question Reading serial ports

stevewidget

Member
Licensed User
Hello,
I have a system that sends data from a micro( various, so not B4R compatible) down serial in response to a request from the PC, all in plain ASCII.
Example Request = ? ( No CRLF needed)
Response is in form of a number of channels (Label)(ASCII Value+ or-)( : delimiter) again no CRLF needed
eg send ? response A-123;B65;C123245678; etc
This all seemed to work fine when I did it via keyboard, after I modified to send CRLF by using Chat example and doing a select case looking for specific labels as in

B4X:
Sub AStream_NewData (Buffer() As Byte)

    Dim s As String = BytesToString(Buffer, 0, Buffer.Length, "UTF8")
    Dim i As Int = 0
    Dim length As Int
    length = s.Length
    Dim temp As String
        Select s.CharAt(i)
            Case "X"
                Do While (s.CharAt(i+1)<>";")
                    i=i+1
                    temp = temp & s.CharAt(i)
                Loop
                lblXval.Text=temp
            
          'add extra cases
        End Select
    Log(length)   
    'LogMessage("You",  temp)
End Sub

So I then set up a timer to issue a '? CRLF' every 200mS, and it crashes after 6-12 readings with an out of range error in i in temp =temp bit. ( Im running at 115200 baud so should be able to cope with 20 characters in this time)
When run the log shows a length of 20 ( correct ) most of time, but sometimes reports 2 numbers that add up to 20 eg, 13 then 7. I don't understand how the buffer is being filled. I sorta assumed that it wait till it got a CFLF so length should always be same.
I cant see a way of controlling the reading of the bytes, or putting in to a smart string to extract each channel data, though Im sure its dead easy when you know what you are doing. Any suggestions please.
Steve
 

emexes

Expert
Licensed User
Anyway taking out the echo fixes issue. Dont understand why the analyser didnt pick it up. Glad I only used trial version.
It was fun while it lasted, I quite enjoy chasing down problems like this. 🍻 I could feel your frustration with it, though. Fog of war and all that too.
I did learn some neat stuff about Regex in the process.
Yeah, when they fit the task, they are like magic. Cryptic magic, admittedly. 🙃
 
Upvote 0

Similar Threads

Top