FullDuplexSerial Tx problem

OlovA · 2009-03-01 17:13

Hi. Does anyone know how to check if the "tx-buffer" is ready to receive new data ?

As it is now, i must wait after two byte of data until i put new data there for transmit.

Maybe i do something wrong...

Thank´s / Olov

Mike Green · 2009-03-01 17:31

Here's one example. This would need to be added to the source of FullDuplexSerial

PUB txflush

'' Wait for transmit buffer to empty

  repeat until tx_tail == tx_head

It's not quite what you asked for. Here's one that waits for some room in the buffer

PUB txwait

'' Wait for transmit buffer to have room for one character

  repeat until (tx_tail <> (tx_head + 1) & $0F)

Note that the "$0F" assumes that the transmit buffer is 16 bytes in length. If you're using some other
buffer size, you'll have to change the constant appropriately.

Post Edited (Mike Green) : 3/1/2009 5:38:00 PM GMT

OlovA · 2009-03-01 20:29

Hi Mike, Thank's for the answer. I still have problem.
What i want to do is, receive 8 bytes of Hex-data from pin 10 ( That works )
Then i want to do something with it ofcourse, and send that data back to the host...

If i send it without delay between the byte's, then after 3 byte's it doesn't send anymore.
But if i insert a delay in the transmission routine it work's ( But then i get timeout at the host-side )

I'll try to attach two pic's so u might understand what's happening...

OlovA · 2009-03-01 20:36

CON
 _clkmode = xtal1 + pll16x
  _XinFREQ = 5_000_000
OBJ
  Serial : "FullDuplexSerialISD"  ' The only difference is that i insert Mike's TxFlush in this one
VAR
  Byte ModBusStr[noparse][[/noparse]8],Ptr
  word CRC
PUB Go 
  Serial.start(10,8,0,57600)    ' RxPin,TxPin,Mode,Baudrate
  'Serial.start(31,30, 0, 57600)
  DirA[noparse][[/noparse]9] := 1                  ' My pin for RS485 TxEnable
  repeat                        ' Pointer for received characters
    Ptr := 0
    repeat
      ModBusStr[noparse][[/noparse]Ptr] := Serial.Rx  ' Store in this variable
      ptr++
    while Ptr < 8                  ' Until 8 char. received
    
    Serial.RxFlush                 ' Clear the RX buffer
    
    If ModBusStr[noparse][[/noparse]0] == $01         ' Check to see that the message starts with $01
      Ptr := 0
      OutA[noparse][[/noparse]9] := 1                 ' RS485 TxEnable
      repeat  
        Serial.Tx(ModBusStr[noparse][[/noparse]Ptr])  ' Transmit the received char.
        WaitCnt(Cnt+10000)         ' Wait for some reason ???
        ptr++
      while Ptr < 8                ' Until 8 char. sent
      OutA[noparse][[/noparse]9] := 0 
'   01040000000131CA               ' A "Dummy" for test via "terminal window"

Mike Green · 2009-03-01 20:41

I don't know what changes have been made to FullDuplexSerial to get FullDuplexSerialISD, so that might be an issue.

With FullDuplexSerial, your "Fail" program should work. I don't know how you've connected the PC to the Propeller.
From the "485" in the names of your pictures, I suspect that you're trying to use a half duplex RS485 setup to
communicate. If so, you have to wait for the transmit buffer to empty before "turning the line around", then you
have to wait for the transmit routine in the assembly cog to finish transmitting the last byte itself. You can approximate
that by waiting until the transmit buffer is empty, then wait around 1 to 1.5 character times. Essentially use the "txflush"
routine I showed, then wait (with WAITCNT) around 200us for the last character to be transmitted.

OlovA · 2009-03-01 21:17

Maaaaaaany Thank's Mike, this problem have made my scull loose some (more) hair. But now it work's thank's to YOU!
I didn't think of the Tx Cog like that! When u told me it maked the coin fall down ( Swedish to english translation !!! )

But anyway, yes that's it. Now it works like it should do. Again, MANY thank's Mike. From a snowy and cold Sweden / Olov.

Mike Green · 2009-03-01 22:39

From snowy and cold Minnesota to snowy and cold Sweden, you're welcome.

FullDuplexSerial Tx problem

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