[En-Nut-Discussion] FW: RE: Nokia LCD Display on Olimex SAM7-EX256 running

[Ole Reinhardt]

Hi,

> >  I just got the Nokia handy lcd display of my olimex sam7-ex256 board running. If anyone is interested in the demo code, please drop me a line via private mail.
> >   
> I'm not sure who was quoting who...

I was the one who announced the display demo :)

> For those that are interested: There is a *VAST* amount of information 
> about this LCD here:
> Written by James Lynch - very informative guy.
> 
> http://www.sparkfun.com/tutorial/Nokia%206100%20LCD%20Display%20Driver.pdf

That was my starting point and his code is used in this demo as well.
The code is somewhat lousy and has several bugs. But for a quick
overview about this display it's a real gold mine.


> --- And some more information about it ---
> 
> Jim made an assumption that you cannot read from one of the LCD controllers
> I sent him the below email - and his response.

Cool! That'll make thinks easy for probing! 

Thanks!

Ole

> 
> Hi Duane.
> 
> By the way, Happy New Year!
> 
> Thanks for pointing out how one can "read" from the Philips controller via
> SPI. I had incorrectly assumed that the absence of the SDOUT pin indicated
> that it was a "no connection" - I stand corrected.
> 
> The truth is, there isn't much to be read from one of these controllers so
> it may not be worth the effort to go through all the trouble you suggest.
> 
> Cheers,
> Jim Lynch
> 
> 
> On 27/12/2007, Duane Ellis XXXXXXXXX wrote:
> 
> > >
> > > Hi, I read your PDF about the nokia display on the olimex sam7-ex256.
> > > Nice work.
> > >
> > > FYI - depending on the LCD type - if it is PCF8833 based - you can read
> > > the display controller back.
> > > You just cannot do so with the at91-SPI hardware controller, instead you
> > > must bit-bang the SPI in "multi-drive" mode
> > > and use either the on-chip pull up resistors or an off chip one.
> > >
> > > Specifically See the PCF8833 - PDF - paragraph 9.0 Serial Interface.
> > >
> > > "The pcf8833 is connected to the SD pin of the micro controller by two
> > > pins SDIN (data in) and SDOUT (data output) which are connected together"
> > >
> > > And there lies the problem, atmel's silicon implementation of the SPI
> > > only operates in "push-pull mode" and no other mode.
> > >
> > > Hence, you send a read command - the SPI controller *continues* to drive
> > > the MOSI pin - per pcf8833 datasheet "are connected together" and thus
> > > you cannot read it.
> > >
> > > If you configure the GPIO pins as bit-bang "multi-drive" (aka:
> > > open-collector/open-drain mode) when you reach the point where SD pin
> > > switches from DATA IN to DATA OUT ... you must stop driving the signal
> > > (in Multi-drive case, you just drive a 1 and let the pull up do it's job).
> > >
> > > ie: Page 72, section 9.2 "Read mode" - 3rd paragraph: "After the read
> > > command has been sent, the SDIN line must be set to 3-state no later
> > > then ..."
> > >
> > > Sadly - the EPSON - you cannot read. However ... (a) if you can read -
> > > you can confirm it is a pcf8833, if you cannot - ie: always 0xfffffff
> > > (pullup) then by default, it must be the other.

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