Simple READ help


silogarrett

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Hi Guru!

I send commands to my frequency inverter and I get a response as shown:

Tx (16:07:22.725): \x02\x0C\x00\x00\x00\x00\x00\x00\x00\x04\x7E\x00\x00\x74
Rx (16:07:22.734): \x02\x0C\x00\x00\x00\x00\x00\x00\x00\x0F\x31\x00\x00\x30
Tx (16:07:22.826): \x02\x0C\x00\x00\x00\x00\x00\x00\x00\x14\x7E\x00\x00\x64
Rx (16:07:22.836): \x02\x0C\x00\x00\x00\x00\x00\x00\x00\x0F\x31\x00\x00\x30

Question is, how do I READ the Rx response? I mean, I can translate it once I get it, but I just don't know how to get in into a channel.

The Rx does not repeat, it's a one-time response. I've tried the following to no avail:

private string datain
// get us lined up:
//device.DIVERTER.purge()
datain = device.DIVERTER.readuntil(56)
while(1)
   try
	  datain = device.DIVERTER.readuntil(56)
	  FI_OUTPUT.addvalue(tranpose(asca(left(datain,56)),1))
   catch()
	  ? strLastError
	  delay(0.5)
	  // realign:
	  device.DIVERTER.purge()
	  datain = device.DIVERTER.readuntil(10)
   endcatch
   delay(1)
endwhile

I get a "C1136 Timeout: READ_STUFF Line 24 - Uncaught error in sequence READ_STUFF"

Can you guide me?

Mike

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Your probably getting timeout because you are doing readuntil() without actually sending the query to the device. So you are basically waiting for an answer without asking a question! You probably want something that looks like this:

purge()
while(1)
   try
	 write(...)
	 readuntil(56)
	 ...
   catch()
	  ? strLastError
	  purge()
   endcatch
   delay(1)
endwhile

The above is, of course, pseudocode, but you get the idea.

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Hi Guru!

Here's my attempt using your guidance:

device.SORTER.Purge()
while(1)
   try
	  device.SORTER.Write(chra({0x02,0x0C,0x00,0x12,0xCF,0x00,0x01,0x00,0x00,0x04,
0x7F,0x35,0xB8,0x24}))  // poll param 719
	  delay(0.1)
	  datain = device.SORTER.readuntil(56)
	  device.SORTER.readuntil(56)
	  FI_OUTPUT.addvalue(tranpose(asca(left(datain,56)),1))
   catch()
	  ? strLastError
	  //device.SORTER.Purge()
   endcatch
   delay(1)
endwhile

But I'm still getting C1136 Timeout errors on line 10. Am I counting enough spaces - is 56 correct? I wanted to simply specify the last hex value received, but then I realized the last character received is a hex block checksum - and it's not always the same value.

Can you explain what I'm doing wrong?

Mike

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I think you misunderstand the readuntil() function. It doesn't read 56 characters, but rather reads the input buffer until it finds the ASCII code 56 (or binary 56 depending on your point of view), or times out. You are getting a timeout because you do readuntil() twice, but only do a single write. You probably can eliminate the second readuntil() and things will work a little better.

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  • 1 year later...

Hi Guru,

A year later, I'm back to this topic. I'm still having trouble with reading from my frequency inverter.

Here's my latest sequence:

// VARIABLES: PRIVATE
private string datain
private data

// SEQUENCE:
try
   device.DIVERTER.Purge()
   device.DIVERTER.Write(chra({0x02,0x0E,0x00,0x12,0xD2,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xCC}))  // chk status
   datain = device.DIVERTER.readuntil(242)  // read until 0xF2
   data = asca(datain)
   RELAY_STAT.addvalue(data)
catch()
endcatch
// END SCRIPT

After execution of the sequence, the screengrab of the Comm monitor looks like this:

Tx (14:44:00.691): \x02\x0E\x00\x12\xD2\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xCC

Rx (14:44:00.701): \x02\x0E\x00\x12\xD2\x00\x00\x00\x00\x00\x00\x0F\x31\x00\x00\xF2

Exactly what I expect, but for the life of me, no matter what I try, I cannot accomplish the READ. The channel did get an entry, but it is NaN. The DATAIN and the DATA always come up NaN. I've tried ?Datain and I get NaN - which doesn't make sense if its a string - at least to me.

I've tried AscA, Asc, Chra, Chr, GetLength, parsing, everything I can think of to see what Datain looks like. No success.

I am assuming that \xF2 in the Rx equals the ASCII 242, and thus my ReadUntil(242). I've also tried Read(0) and Read(1) to no avail. Please SHOW me what to do to accomplish this simple task?

PLEASE HELP!

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The script looks ok, but something else might be wrong. First, always put:

? strLastError

inside catch() blocks, at least until you finish debugging, otherwise, any errors are just ignored and thus probably just throwing away the answer to your problem.

Second, try changing "datain" to something else, like "strDataIn", just in case there is a name conflict with dataIn, not that I see one.

Finally, you realize that you are adding the entire array of bytes to Relay_stat? You probably just want data[11] or [12] or something, though you aren't this far yet.

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