rxtime or rxcheck question

steprog · 2010-12-01 23:40

Hi Guys,
Does rxtime or rxcheck corrupt the incoming string if you use it?
Thanks,
Greg

kuroneko · 2010-12-01 23:57

steprog wrote: »

Does rxtime or rxcheck corrupt the incoming string if you use it?

rxtime uses rxcheck, the latter returns either the oldest received character or -1 indicating that there isn't one. So if there is one then it consumes a character (by returning it to you). I assume you use said function in a simple yes/no manner which - if not handled properly - loses characters.

What does your code look like?

steprog · 2010-12-02 00:19

MsgTest:==debug.rxtime(100)
getstr(@command)
if strcomp(@Reset, @command)
do stuff

From what your telling me my string compare won't work too well.

kuroneko · 2010-12-02 00:28

steprog wrote: »
MsgTest:==debug.rxtime(100)
  getstr(@command)
  if strcomp(@Reset, @command)
   do stuff
From what your telling me my string compare won't work too well.

Let's say you receive the string "fred\n" ('\n' being the end of the line/string). Depending on timing MsgTest will either be -1 (timeout) or 'f'. Then getstr will assemble the string "fred" or "red". So in case you didn't get the timeout you want to recover the missing/consumed character.

steprog · 2010-12-02 00:31

Now how to do that
Thanks for the help.
Greg

kuroneko · 2010-12-02 00:34

steprog wrote: »

Now how to do that
Thanks for the help.
Greg

getstr looks like one of your methods, so why don't you pass in an extra parameter (i.e. MsgTest) which when -1 is ignored otherwise inserted into the buffer before the serial device is read again?

steprog · 2010-12-02 00:38

Sounds interesting, but for the life of me I can't picture how to implement it.

kuroneko · 2010-12-02 00:46

steprog wrote: »

Sounds interesting, but for the life of me I can't picture how to implement it.

I'd help you but I'd need to see more code in order to do so. An example would be ...

VAR
  byte  command[16]
  
PUB null

  if (MsgTest := debug.rxtime(100)) <> -1               ' got character
    command[0] := MsgTest                               ' recover character
    getstr(@command[1])                                 ' append remainder of string
    if strcomp(@Reset, @command)
      do stuff

steprog · 2010-12-02 00:47

You have been more help than I deserve. Thanks a bunch.
Greg

Ariba · 2010-12-02 03:59

You can also add a new methode to the FullDuplexSerial object, which returns the number of waiting bytes in the buffer. This does not change the buffer.

PUB rxcount : count

'' Check for bytes in receivebuffer (never waits)
'' returns the number of bytes 

  count := (rx_head - rx_tail) & 15

Andy

rxtime or rxcheck question

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