Option explicit
dim S_Timeout,s_port

print "Wait for 10 seconds then print all characters waiting in Rx buffer"
' example: call routine, wait 10 seconds then print all characters
'   entered from console (s_port = 0)
print SerIn$(10,0)

function SerIn$(S_timeout,s_port)
' function to wait S_Timeout seconds from current time and
' return all characters waiting in Rx buffer of COM port s_port
' Note: this is a blocking routine
 local tout,start_secs,s_chars$
 tout = S_timeout
 start_secs = T_now()
 do
 loop while T_now() < start_secs + tout
 s_chars$ = input$(255,s_port) ' will get up to 255 characters from com port
 SerIn$ = s_chars$
end function
   
Function Time_now(arg1) ' arg1 unused
' returns current time in seconds, does not cater for day over-run
 local t_n
 t_n=(val(left$(time$,2))*3600)+(val(mid$(time$,4,2))*60)+val(right$(time$,2))
 T_now = t_n
end function

Option EXPLICIT

const maxto = 500  'exemple time out 5 sec
dim cptto as integer  'count time$
dim flgeot as integer

SETTICK 10,sptim
Open "COM1:9600,255,spcomrec" As #2

flgeot=0


do

'  if need to read serial
 cptto=maxto
 ....
 if flgeot=1 then
flgeot=0
.....   'task receive text
 end if
'
...
'if no need read serail
 cptto=0
 

loop

sub sptim
 if cptto>0 then  'if cptto=0 then do nothing
   cptto=cpto-1
   if cptto=0 then 'if end of time-out do task "timeout"
     ....
   end if
 end if
end sub

sub spcomrec
Local tx$ As string
Local i2 As integer
Local a$ As string length 1
 nbcar=Loc(#2)
 If nbcar>0 Then
   tx$=Input$(nbcar,#2)
     cptto=maxto
     'do task read serial
       'exemple
       For i2=1 To nbcar
         a$=Mid$(tx$,i2,1)
         If (asc(a$)=13 or asc(a$)=10) Then  'end rec texte
             .....
           flgeot=1
         end if
       next i2
 end if
end sub

SUB conINP(tm)
 TIMER = 0
 DO WHILE((inp$ = "") AND (TIMER < tm))
   inp$ = INKEY$
 LOOP
END SUB

SUB conINP(tm,inp$,stat%)
' stat%=0 if sub in work (no timeout and waiting key$)
' stat%=1 if end on time-out
' stat%=2 if end on inkey buffer not empty and inp$=key$
local vtm as integer
 vtm = TIMER
 inp$ = ""
 stat% = 0
etq1:
 if  TIMER - vtm > tm then stat% = 1: exit sUB
 inp$ = INKEY$
 if inp$ <> "" then stat% = 2: exit SUB
 goto etq1
END SUB