Werner Almesberger werner at openmoko.org
Tue Apr 14 07:06:22 CEST 2009

Steve Mosher wrote:
>  Ya.. In PVT you have some slop. Its basically a yeild/cost question.
>  I've shipped product with a 50% yeild ( first batch) because

Hah, there would have been blood on the factory floor had we tried
this :-) One problem with the factory was that the business
arrangement with them made our yield problems their loss. So when
things wend wrong, they started to put pressure on the poor folks
Openmoko had sent there.

>>   - add a NAND trap-door circuit
>       Explain please.

The idea is to add a flip-flop to control the write protect line of
the NAND. A system reset enables writing and a GPIO disables writing
(until the next system reset). That way, the boot loader can lock
the NAND, or it can choose to leave it unlocked, e.g., to allow an
upgrade of itself.

This would be a mostly-unbrickable solution provided that the boot
loader doesn't change much. A bit tougher than GTA01 but not as
robust as GTA02.

By the way, I use the general term "boot loader" because that could
be either Qi or even some kind of first stage, similar to the boot
ROM in 6410.

>>   - integrate IDBG
>       HA. ok I'll look at it again. I'm more amenable this time around
>       since I have attach rates for debug and better cost data and Some
>       anecdotal info on the failure rates of the flex cable. You don't
>       give up. I like that.. sometimes. So A fresh look.

Hehe, thanks :-) One aspect that isn't directly in your data: for
some debugging tasks, you need the serial console. So sometimes
we didn't get the logs we would have wanted because people didn't
have a debug board.

For GTA03, we actually found that we could make either IDBG or the
"new" debug connector a BOM choice using the same layout.

- Werner

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