Does that mean a breakout board release is imminent?


----- Original Message ----
From: Craig Hughes <>
To: Julien Lebot <>
Sent: Friday, June 22, 2007 1:43:09 PM
Subject: Re: [Gumstix-users] Gumstix PSP LCD

I got it working.  The problem was the backlight voltage was set way  
way way too low, so I just couldn't see anything, although it had  
been working.

I've got code on my 270 branch to support this screen which has  
correct timing info on it:



On Jun 22, 2007, at 10:02 AM, Julien Lebot wrote:

> On May 25, 2007 at 01:35am Craig Hughes wrote: "I've not yet been able
> to get the pxafb to get images onto  the screen though, despite a lot
> of debugging and datasheet reading.  I suspect I'm pretty close and
> just overlooking some elementary  thing."
> Hello,
> I'm working on that too, is the problem related to the timing  
> settings ?
> I have spent my whole day in front of the oscilloscope fiddling with
> the timings, unsuccessfully.
> I have took apart my PSP so I could see the timings and compare it to
> what I get from the Verdex, just to make sure I was reading the
> datasheet properly.
> The first problem come from the bias pin, aka Output enable, which
> switch on and off. On the PSP this line never changes, it's switching
> on/off at the same time as the backlight, according to the datasheet.
> With this issue solved I'm able to see the pixels coming online but
> still nothing is displayed.
> Secondly, I just cannot figure out how the pxafb options are  
> related to
> the timings. I know that pixel clock is in KHz, correct me if I'm
> wrong, so I've put pixclock 9000 for 9MHz.
> In /documentation/fb/pxafb.txt it is said that pixclock is in
> picoseconds which does not make sense since the corresponding  
> frequency
> is in GHz.
> Then Hsynclen, Vsynclen, left, right etc... what are their units ?
> Does left/right stand for the Horizontal front/back porch of the PSP's
> datasheet ? Then upper/lower stand for Vertical front/back porch ?
> I tried to set a few parameters and play with only one but I get
> strange results, eg for hsync:
> hsynclen 41 (in the datasheet it's stated 41clock) leads to a pulse
> width around 2Ás
> hsynclen 10 => ~0.3Ás
> hsynclen 150 => ~0.86Ás
> hsynclen 1000 => ~1.65Ás
> hsynclen 120 => ~2.3Ás
> hsynclen 60 => 3Ás (the longest I have been able to get)
> The correct length should be 5Ás(actually 4.55Ás).
> Changing left/right change the period in a way I have not figured  
> out too.
> Julien

This email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
gumstix-users mailing list

Fussy? Opinionated? Impossible to please? Perfect. Join Yahoo!'s user panel and lay it on us.