Re: [Lcd-linux] lcd over gpio

[Claudio <cla...@gm...>]

2011/1/18 Mattia Jona-Lasinio <mat...@gm...>:
> On Tue, Jan 18, 2011 at 1:12 PM, Claudio <cla...@gm...> wrote:
>> Dear mattia,
>> let me introduce a different scenario.
>>
>> The USB device are really different each other and support for its
>> could be difficult and inefficient, beside on embedded devices
>> generally you want to use the USB port for something more useful.
>
> Hmmmm, quite a lot of people might disagree with you as USB is now
> considered THE universal and preferred way to connect external devices
> to computers. Anyway, I see your point.
>
>> The gpio implementaion instread allow you to support a huge range of
>> embedded devices like router, develop board as well some routerboard
>> or industial board; moreover you can use a USB to GPIO adapter (like
>> ftdi) and then connect any kind of lcd also on you modern laptop/pc
>> (that typically don't have parport or gpio).
>
> I agree and this should in principle be very easy. If the GPIO
> implementation in the kernel is at a usable level then I'm more than
> happy to try to use it. In any case it will provide a sort of standard

I can tell you that a lot of interface are yet build on top of gpio
layer for example i2c or spi bus, as well as led, buttons (for input)

i2c http://lxr.linux.no/#linux+v2.6.37/drivers/i2c/busses/i2c-gpio.c
spi http://lxr.linux.no/#linux+v2.6.37/drivers/spi/spi_gpio.c
buttons http://lxr.linux.no/#linux+v2.6.37/include/linux/gpio_keys.h#L17

> way to access the display. If this is the case then it is very easy as
> the only two functions in the HD44780 driver that need a rewrite are
> the two lowlevel read and write functions. If I write a patch, will
> you be able to test it and report on it?
>

Yes of course!