[gta02-core] -1 Hardware revision stored in EEPROM

Rask Ingemann Lambertsen ccc94453 at vip.cybercity.dk
Thu Aug 27 15:58:43 CEST 2009

On Wed, Aug 26, 2009 at 09:19:31PM +0100, Dave Ball wrote:
> Álvaro Lopes wrote:
> > I must confess I agree in priciple.... but this presents some other problems - it has to be programmed either before or after assembly.
> >
> > And we do not use most of CPU pins, so we can use them just for now. 
> I agree.  I personally like having real HW revision detection so it's 
> easy to change the board revision if/when mods are made to each of the 
> prototypes with solder blobs, and visually confirm the revision.

   How about using the analog inputs ANx instead? We can encode several bits
per pin that way. Some of the SMD packages are large enough that resistor
values are printed on them.

> Maybe we should move it to GPA17/18 to avoid the EINTs, but we only 
> really gain if we end up using those EINTs for something else...
> I've not dug into the datasheet, but would doing something with gpa0-8 
> be less risky?

   From the datasheet: "Port A(GPA): 25-output port".

> Freeing up the camera port for IO might be nice, but I think I'd rather 
> leave those lines as they are in gta02.  Less mistakes for us to make!

   Then the gta02-core will be completely uninteresting for hardware
hackers. Notice how few DIY hardware projects have been made for the GTA01
(after two years) or the GTA02 (after one year) - really just Werner's IDBG.
That's simply because they offer so little in the way of interfacing
hardware addons. This is a mistake I would like gta02-core to avoid.

   Also, if we don't have anywhere to connect hardware addons, we also miss
one means of prototyping the next round of hardware developments. You can
use WLAN over SPI in gta02-core as an example. Using a GTA02 to prototype
WLAN over SPI came to the rescue when Werner couldn't get the prototype
board to work[1]. The spare SPI on the debug connector came in handy.[2]

[1] https://lists.openmoko.org/pipermail/openmoko-kernel/2008-August/004626.html
[2] https://lists.openmoko.org/pipermail/openmoko-kernel/2008-September/004922.html

   For an example of the problems DIYers are facing with the GTA02, at least
two people have looked into adding a camera to a GTA02[3] and half a year
later they haven't succeeded. That's disappointing considering that a 1.3
Mpix camera module costs less than $10 [4] and has a relatively simple I2C +
8-bit parallel interface.

[3] https://lists.openmoko.org/pipermail/hardware/2009-January/000942.html
[4] https://www.sparkfun.com/commerce/categories.php?c=102
Rask Ingemann Lambertsen
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