Subj : Re: Need to write putchar for embedded system
To   : comp.lang.c,comp.programming
From : Confused User
Date : Fri Jul 01 2005 09:30 am

Gordon & Jack,
A lot of helpful input. Thanks a lot!
I do want to elaborate on a few points and ask further questions, however,
it is 8:30am and I have to get to work. This info will help me today.

I will be back later for some further discussion on this topic.

Thanks again,

Elvis
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"Confused User" <elvis_is_king@bellsouth.net> wrote in message
news:X31xe.6050$du.1033@bignews1.bellsouth.net...
> I am working on device that utilizes a Motorola 68HC16 microcontroller. I
am
> using an old unsupported piece of crap Whitesmith's / Intermetrics /
Tasking
> compiler. The embedded compiler business was quite insestual for while
> wasn't it? I need to write putchar so that printf can function properly.
>
> Anyway, the compiler comes with just a shell of a putchar routine. It
> literally returns the character you passed to it and nothing else. That is
> not why it's a piece of crap, although they could have at least supplied
> something that writes to the serial port.
>
> So, I already have a serial port interrupt routing with circular buffers
> (in/out) and a function call (SendData()) that copies a data from a
pointer
> argument and manages the circular buffer. So, I want to have my putchar
> routine call SendData.
>
> I noticed from looking around that putchar returns EOF if unsuccessful.
EOF
> is defined as -1 in the compiler header file. Therefore, it occurs to me
> that putchar can only be used for ASCII data. This is OK, I just need to
> make sure I have that right. Because, binary data could include -1 right?
> That means I should never use it alone to send binary data. If so, is this
> true for the PC? After all, it's counterpart, getchar retrives binary scan
> codes from the keyboard unless they have already been converted to ASCII
> characters before they get to that level.
>
> I would guess the only time getchar should return EOF is if the transmit
> buffer is full. My SendData() function already is set to return a fail
code
> if the buffer is full. putchar can pass this on to printf (of course I
have
> to change SendData() to use EOF as a fail code).
>
> As an embedded programmer, I am not real familiar with what normal
pass/fail
> return codes should be. The high level languages were developed around
full
> OS systems (Unix etc.) and then seem to have migrated to the embedded
world
> leaving some us without familiarity of conventions.
>
> Enough rambling.... Just looking for any constructive input.
>
> Elvis
>
>

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