Re: [ECOS] Termios and waiting for character input

[Gary Thomas <gary@mlbassoc.com>]

Andre-John Mas wrote:
> Where do I change the VMIN value? I'll change the value to see
> if this helps.
> 
> BTW I had worked around the issue by simply doing a loop until
> the input value was not 0x0. Not very elegant when CPU cycles
> matter. I also made the same observation as Gary that the code
> worked on other systems. I had tested the same code on MacOS X.

It's just another parameter to the termios structure.  Simply
add this line:
   term = termsave;            /* termsave contains old termios */
   term.c_lflag &= ~ECHO;      /* turn off echo if it's set */
   term.c_lflag &= ~ECHOE;     /* turn off echoe if it's set */
   term.c_lflag &= ~ICANON;    /* turn off echoe if it's set */
   term.c_cc[VMIN] = 1;

> Andre
> 
> Jonathan Larmour wrote:
>> Gary Thomas wrote:
>>> Jonathan Larmour wrote:
>>>> Gary Thomas wrote:
>>>>> Jonathan Larmour wrote:
>>>>>> Non-canonical mode processing was only implemented to support 
>>>>>> VMIN=0,TIME=0. Support for VMIN>0 is rudimentary and I wouldn't 
>>>>>> trust it. But VMIN defaults to 0, and that sample code posted 
>>>>>> doesn't attempt to set it to anything else.
>>>>>>
>>>>>> I imagine it defaults to something else on Linux, hence the 
>>>>>> difference in behaviour. <fx: goes and checks> Aha, in fact it 
>>>>>> defaults to 6. The POSIX standard does not set any requirements for 
>>>>>> the default value, so eCos is fine on this count.
>>>>> Thanks for looking into this.
>>>>>
>>>>> Perhaps we should make the default values for VMIN/VMAX configurable,
>>>>> possibly with settings that match other systems?
>>>> Maybe so if I had more confidence it worked! If Andre-John (or 
>>>> yourself) can play around with VMIN>0 and don't find any problems, 
>>>> then we could change the default for VMIN. NB there is no VMAX, but if 
>>>> you meant TIME, then TIME>0 is definitely unsupported in the current 
>>>> code.
>>> It does work correctly (or at least the same as Linux) when VMIN=1.
>>> If I set VMIN=6, then I have to type 6 characters before the first one 
>>> is seen.
>>> Perhaps that's where a setting of TIME>0 would matter...
>> Yes indeed, that's the correct behaviour for TIME=0. So maybe it does work, 
>> and we could set default VMIN to 1.
>>
>>> At least we could have a way to default the value of VMIN and document
>>> the fact that TIME>0 is not implemented (if not already in the docs)
>> Since VMIN can be set in a well-known and standard way at run-time, I'm not 
>> sure there's much value in a configuration option for the default.
>>
>> Termios is unfortunately undocumented. This was in the days when making doc 
>> edits happen was like pulling teeth. And it became one of those things that 
>> just never happened.
>>
>> Jifl
>>


-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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