lcd4linux-devel

[Lcd4linux-devel] Time-out for picoLCD 256x64

[Martin Z. <co...@mz...>]

Hello everybody,

I had written that polling the button states using LCD::GPI(1)
considerably slows down output on my picoLCD 256x64 and located the
problem in this function:

   static int drv_pLG_read(unsigned char *data, int size)
   {
     return usb_interrupt_read(lcd, USB_ENDPOINT_IN + 1, (char *) data,
     size, 1000);
   }

On second thoughts, I have made the mistake to think that this function
times out *every* time.  When a key is pressed, however, the function
exits directly and thus only times out when no data are present for
usb_interrupt_read().

This means that the time-out value is *much* too high.  The driver 
usually waits a *full second* for key data before going on and doing 
(more important) things like updating the LCD.  As this makes the 
display rather unresponsive, I think that the time-out value should be 
changed.

My problem is that I don't know what time-out value should be used.  I
have experimented a little: 1 ms is too low, while 2 ms work fine on my
desktop.  On my embedded system, 3 ms are needed.  But what about people
using the display with an old USB 1.0 port?  I propose 5 ms or 10 ms --
what do you think?

Thanks,

Martin
-- 
www.mzuther.de
www.radix-musik.de

Re: [Lcd4linux-devel] Time-out for picoLCD 256x64

[Michael R. <mi...@re...>]

Hi Martin,

> I had written that polling the button states using LCD::GPI(1)
> considerably slows down output on my picoLCD 256x64 and located the
> problem in this function:
> 
>    static int drv_pLG_read(unsigned char *data, int size)
>    {
>      return usb_interrupt_read(lcd, USB_ENDPOINT_IN + 1, (char *) data,
>      size, 1000);
>    }
> 
> On second thoughts, I have made the mistake to think that this function
> times out *every* time.  When a key is pressed, however, the function
> exits directly and thus only times out when no data are present for
> usb_interrupt_read().

Well, this means the picoLCD does not answer with something like "zero keys pressed", but just times out?

Sounds *a little bit* braindamaged to me ;-)

> My problem is that I don't know what time-out value should be used.  I
> have experimented a little: 1 ms is too low, while 2 ms work fine on my
> desktop.  On my embedded system, 3 ms are needed.  But what about people
> using the display with an old USB 1.0 port?  I propose 5 ms or 10 ms --
> what do you think?

I's recommend a value of 5 msec, and make it a config option within the display section


HTH, Michael

-- 
Michael Reinelt <mi...@re...>
http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
ICQ #288386781

Re: [Lcd4linux-devel] Time-out for picoLCD 256x64

[Martin Z. <co...@mz...>]

Hi Michael,

I don't argue with you, the picoLCD *is* brain damaged.  But there is 
good in it, as well.  Without this brain damage, I wouldn't have had a 
go at the timers... ;)

> I'd recommend a value of 5 msec, and make it a config option within the display section

So be it, I've just committed.

Thanks,

Martin
-- 
www.mzuther.de
www.radix-musik.de

Re: [Lcd4linux-devel] Time-out for picoLCD 256x64

[Michael R. <mi...@re...>]

Hi Martin,

> I don't argue with you, the picoLCD *is* brain damaged.  But there is
> good in it, as well.  Without this brain damage, I wouldn't have had a
> go at the timers... ;)

Think pink, eh? ;-)

>> I'd recommend a value of 5 msec, and make it a config option within
>> the display section
> 
> So be it, I've just committed.

Looks fine. Maybe you want to add some kind of limiting? What happens if the silly user specifies a timeout of 0 (zero)?
or even worse, -1?


bye, Michael (fighting the flu)


-- 
Michael Reinelt <mi...@re...>
http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
ICQ #288386781

Re: [Lcd4linux-devel] Time-out for picoLCD 256x64

[Martin Z. <co...@mz...>]

Hi Michael!

> Looks fine. Maybe you want to add some kind of limiting? What happens if the silly user specifies a timeout of 0 (zero)?

Oops, got me!  Actually, a USB read that never terminates is my idea of 
punishing silly users... :)

Fixed.

Martin

P.S.: Gute Besserung!
-- 
www.mzuther.de
www.radix-musik.de