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

[duane ellis]

Lokker, Ronald wrote:
>  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...

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

--- 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.


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.
> >
> > ---
> >
> > Once the type is know, flip back to hardware based SPI.
> >
> > -Duane.
> >
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