SUB ComISR
DO WHILE LOC(#2)   ' LOC returns the number of bytes waiting
 ch$ = INPUT$(1,#2)   ' Get single character
 [check for control characters, set flags as required]
 buf$ = buf$ + ch$
LOOP
END SUB

OPEN "COM2:38400" as #2 'Open COM port, default buffer of 256 bytes

...

DO 'Primary loop - EVERYTHING is inside this one...
 DO 'Secondary loop - most actions happen inside this one....
   ...
   ...
   If LOC(#2) then 'There is something in the COM port buffer
     D$=Input$(LOC(#2),#2) 'Suck everything out of the buffer and store it in D$
     IF LEN(D$)<>25 then
       Print "Data length error!"
       Exit Do
     Endif
     CMD$=RIGHT$(D$,5) 'LAST five bytes of string are the command.
     DTA$=LEFT$(D$,20) 'FIRST twenty bytes are the data
   
   Endif
   ...
   ...
 LOOP
LOOP

OPEN "COM2:38400" as #2 'Open COM port, default buffer of 256 bytes

...

DO 'Primary loop - EVERYTHING is inside this one...
 DO 'Secondary loop - most actions happen inside this one....
   ...
   ...
   If LOC(#2) then 'There is something in the COM port buffer
     DO
       X$=Input$(1,#2) 'Suck ONE byte out of the buffer and store it in X$
       IF X$=CHR$(27) then Exit Do 'EOM marker byte detected, so hop out of here...
       D$=D$+X$
     LOOP
     IF LEN(D$)<>25 then
       Print "Data length error!"
       Exit Do
     Endif
     CMD$=RIGHT$(D$,5) 'LAST five bytes of string are the command.
     DTA$=LEFT$(D$,20) 'FIRST twenty bytes are the data
   
   Endif
   ...
   ...
 LOOP
LOOP

If LOC(#2) then 'There is something in the COM port buffer
  DO
     X$=Input$(1,#2) 'Suck ONE byte out of the buffer and store it in X$
     IF X$=CHR$(27) then Exit Do 'EOM marker byte detected, so hop out of here...
     D$=D$+X$
  LOOP

DO WHILE LOC(#2) THEN 'There is something in the COM port buffer
  X$=INPUT$(1,#2) 'Suck ONE byte out of the buffer and store it in X$
  IF X$=CHR$(27) THEN eom = eom + 1
  D$=D$+X$
LOOP

IF eom > 0 THEN ...process... : eom = eom - 1

OPEN "COM2:38400" as #2 'Open COM port, default buffer of 256 bytes

...

DO 'Primary loop - EVERYTHING is inside this one...
DO 'Secondary loop - most actions happen inside this one....
  ...
  ...
  If LOC(#2) then 'There is something in the COM port buffer
    TIMER=0 'Reset the system timer
    D$="" 'Clear D$ for this time through the loop
    DO
      X$=Input$(1,#2) 'Suck ONE byte out of the buffer and store it in X$
      IF X$=CHR$(27) then Exit Do 'EOM marker byte detected, so hop out of here...
      D$=D$+X$
    LOOP UNTIL TIMER>4000 'Exit if more then 4s has elapsed(no EOM detected)
    IF LEN(D$)<>25 then 'This will catch any short or long message
      Print "Data length error!"
      Exit Do
    Endif
    CMD$=RIGHT$(D$,5) 'LAST five bytes of string are the command.
    DTA$=LEFT$(D$,20) 'FIRST twenty bytes are the data
 
  Endif
  ...
  ...
LOOP
LOOP

TIMER=0
DO
 X$=Input$(1,#2) 'Suck ONE byte out of the buffer and store it in X$
 D$=D$+X$
LOOP UNTIL X$=CHR$(27) or TIMER>4000 'Exit if we have an EOM byte, or more then 4s has elapsed
DTA$=LEFT$(D$,(LEN(D$)-1)) 'Copy message into DTA$, dropping the EOM byte from the end

OPEN "COM2: 38400" AS #2                      ' RS485 Channel 2 (receive)

DO
 DO WHILE LOC(#2)                            ' If there are any characters in the UART buffer, loop to get them all out
   s = INPUT$(1,#2)                          '  (including any that come in while we are looping)
   IF s = Delimiter THEN                     ' Incoming data stream delimiter
     EOM = EOM + 1                           ' Counter of non-processed lines waiting for processing
   ENDIF
   PIN(TP35) = HIGH                          ' Debug: Pulse for every character
   IF LEN(Buffer) < MaxBuffer THEN           ' Discard data that would cause a buffer overflow
     Buffer = Buffer + s
   ELSE
     Overflow = Overflow + 1                 ' How many characters got lost (running total)
   ENDIF
   PIN(TP35) = LOW
 LOOP

 IF EOM > 0 THEN
   n = INSTR(Buffer, Delimiter)                ' Search for delimiter (0=not found, otherwise returns position starting at 1)
   IF n = 0 THEN
     IF (Debug AND &b00000010) THEN            ' Debug: buffer has garbage, discard it
       PRINT "Discarding <";Buffer;">"
     ENDIF
     Buffer = ""                               ' Delimiter not found, zero string and counter
     EOM = 0
   ELSE
     s = LEFT$(Buffer, n - 1)                  ' Get everything up to, but not including, the delimiter
     Buffer = MID$(Buffer, n + 1)              ' Shorten buffer. If the length is not specified, MID$ returns everything from 'n' onwards
     EOM = EOM - 1                             '  (n+1 dumps the delimiter)
     IF (Debug AND &b00000011) THEN            ' Debug: print recovered line
       PRINT " [";s;"]";
     ENDIF
   ENDIF
 ENDIF

 IF TOUCH(DOWN) OR (b > 0) THEN                      ' Something pressed (or something previously pressed)?
   ........
 ENDIF
LOOP