1. unbuffered getc() ?
Hi,
I am using Euphoria (2.4 alpha) in Linux to interface with a serial LCD
screen and keypad. Sending output is no problem (once I'd remembered to use
flush() ) but I'm having trouble reading from the keypad. I tried something
like the following:
integer lcd, key
lcd=open("/dev/ttyS1","ub")
while 1 do
puts(lcd,{#FE,#26})
-- this tells the device to return the contents of its key buffer, or if the
-- buffer is empty, to return 0x00
flush(lcd)
key=getc(lcd) --just locks up here!
print(1,key)
end while
This doesn't work because according to the Euphoria docs:
"File input using getc() is buffered, i.e. getc() does not actually go out
to the disk for each character. Instead, a large block of characters will be
read in at one time and returned to you one by one from a memory buffer.
When getc() reads from the keyboard, it will not see any characters until
the user presses Enter. Note that the user can type control-Z, which the
operating system treats as "end of file". -1 will be returned. "
So it seems that getc() won't return anything until Euphoria sees a line
feed or an EOF. So my question (if you've read this far): how can I get a
Euphoria program to read a single byte, immediately and without dealing with
buffers, from a file descriptor. Is there a standard C function I can
easily wrap? (I'm not very good with C)
I hope that made some sort of sense,
chris.
2. Re: unbuffered getc() ?
Erm, no. That won't work through the serial port, or will it? Sorry, I'm
rubbish at explaining things - it's the serial port I'm trying to read from.
chris.
>
> Did you try get_key() and/or wait_key()?
>
> -- Brian
>
> chris wrote:
> >
> > Hi,
> > I am using Euphoria (2.4 alpha) in Linux to interface with a serial LCD
> > screen and keypad. Sending output is no problem (once I'd remembered to
> > use
> > flush() ) but I'm having trouble reading from the keypad. I tried
> > something
> > like the following:
> >
> > integer lcd, key
> >
> > lcd=open("/dev/ttyS1","ub")
> > while 1 do
> > puts(lcd,{#FE,#26})
> > -- this tells the device to return the contents of its key buffer, or if
> > the
> > -- buffer is empty, to return 0x00
> > flush(lcd)
> > key=getc(lcd) --just locks up here!
> > print(1,key)
> > end while
> >
> > This doesn't work because according to the Euphoria docs:
> >
> > "File input using getc() is buffered, i.e. getc() does not actually go
> > out
> > to the disk for each character. Instead, a large block of characters
> > will be
> > read in at one time and returned to you one by one from a memory buffer.
> > When getc() reads from the keyboard, it will not see any characters
> > until
> > the user presses Enter. Note that the user can type control-Z, which the
> > operating system treats as "end of file". -1 will be returned. "
> >
> > So it seems that getc() won't return anything until Euphoria sees a line
> > feed or an EOF. So my question (if you've read this far): how can I get
> > a
> > Euphoria program to read a single byte, immediately and without dealing
> > with
> > buffers, from a file descriptor. Is there a standard C function I can
> > easily wrap? (I'm not very good with C)
> >
> > I hope that made some sort of sense,
> > chris.
> >
> >
>
>
> TOPICA - Start your own email discussion group. FREE!
>
>
3. Re: unbuffered getc() ?
Chris,
I used the following functions to bypass Euphoria's buffering. I
don't know if they'll work for your situation, but give them a try and
let me know.
Michael J. Sabal
------ code follows ---------
function old_getc(object z)
return getc(z)
end function
function getc(integer z)
object temp
if length(inbuffer)<100 then
inbuffer = inbuffer & get_bytes(z,4096)
end if
if length(inbuffer)=0 then
return 0
end if
temp = inbuffer[1]
if length(inbuffer)>1 then
inbuffer = inbuffer[2..length(inbuffer)]
else
if temp = 26 then temp = 0 end if -- if the only char in the buffer
is CTRL-Z, call it end of file.
inbuffer = ""
end if
return temp
end function
--------- end code -------------
>>> tubby.toast at ntlworld.com 05/12/03 04:00PM >>>
line
feed or an EOF. So my question (if you've read this far): how can I
get a
Euphoria program to read a single byte, immediately and without dealing
with
buffers, from a file descriptor. Is there a standard C function I can
easily wrap? (I'm not very good with C)
I hope that made some sort of sense,
chris.
4. unbuffered getc() ?
chris:
Down load this program from the archive.
http://www.rapideuphoria.com/xserial.zip
You should be able to adapt this to linux.
All you need to do is capture the serial port characters
one at a time as they are typed and then send them to the LCD
until you see a Enter or Carraige return.
Bernie
5. Re: unbuffered getc() ?
Hi,
Thanks to everybody who suggested solutions to my problem regarding reading
from the serial port. I tried all the suggestions and more but with no
luck. Then, after playing about with minicom for a bit, I found that the
problem was due simply to a misconfigured serial port. getc() can read a
single byte from the serial port just fine - it wasn't Euphoria's fault at
all. Sorry about that!
chris.
