[gta02-core] Debug connector FPC (Was: Hardware revision stored in EEPROM)

[Werner Almesberger]

Rask Ingemann Lambertsen wrote:
>    Actually, what exactly does the debug connector accept?

Here it is in all its beauty:
http://wiki.openmoko.org/wiki/Connecting_Neo1973_with_Debug_Board_v2

The FPC is single-sided, 0.3 mm pitch on the Neo side, 39 traces. 
Note the lovely Y shape on the way to the debug board.

Mechanical tolerances of this critter are very tight and you get
all sorts of odd problems if it isn't perfectly right, including
intermittent failures.

Once, Openmoko had to change the source for these FPCs. It took
us two or three tries before we got acceptable cables. Some were
a tiny fraction of a millimeter too narrow on the debug board
side. Much fun was had before we figured out that one.

It's also quite common that the Neo side of the cable isn't right,
although this surprisingly rarely causes problems.

I tried for more than a year to kill this spawn of hell at
Openmoko, in the end even "underground". Alas, GTA03 died a few
days too early for the conspiracy to sneak IDBG into the design to
bear fruits.

- Werner