[Lazarus] Serial communication??

[Mark Morgan Lloyd]

Bo Berglund wrote:

> So now I am after a serial comm implementation for Lazarus/Fpc to work
> in a Linux embedded environment which gives me these possibilities.

Yes, and as I've said before I'm using the standard serial unit plus 
fpSelect() without problems. Horses for courses, as we say over here.

Irrespective of what solution you choose one thing that you might need 
to consider is how accurately you can time things. In particular, the 
type of protocol that I work with needs timeouts applied from the point 
where the computer has actually sent the final character of a packet, so 
whatever code is handling your state machine (or whatever) needs to be 
able to see the comms subsystem at that level- not just at an abstracted 
event level.


function SerReadTimeout(Handle: TSerialHandle; var Buffer; mSec: 
LongInt): LongInt;

(* This is similar to Serial.SerRead() but adds a mSec timeout. Note 
that this  *)
(* variant returns as soon as a single byte is available, or as dictated 
by the *)
(* timeout. 
         *)

VAR     readSet: TFDSet;
         selectTimeout: TTimeVal;

begin
   fpFD_ZERO(readSet);
   fpFD_SET(Handle, readSet);
   selectTimeout.tv_sec:= mSec DIV 1000;
   selectTimeout.tv_usec:= mSec * 1000;
   RESULT:= 0;
   IF fpSelect(Handle + 1, @readSet, NIL, NIL, @selectTimeout) > 0 THEN
     RESULT:= fpRead(Handle, Buffer, 1)
end { SerReadTimeout } ;


function SerReadTimeout(Handle: TSerialHandle; var Buffer: ARRAY OF 
BYTE; count, mSec: LongInt): LongInt;

(* This is similar to Serial.SerRead() but adds a mSec timeout. Note 
that this  *)
(* variant attempts to accumulate as many bytes as are available, but 
does not  *)
(* exceed the timeout. 
         *)


On top of those you put whatever state machines etc. that you need.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]