GTA04 Block V4

Werner Almesberger werner at
Sun Aug 17 12:57:40 CEST 2008

Yair Mahalalel wrote:
> I suggest a solution that will have the smallest impact on the rest of
> the system - an 8-bit uC such as Microchip's PIC18LF4550, which will
> stay dormant and waiting when unneeded (at 2V/100nanoWatt,

Yes, we've already come to the conclusion a long time ago that we
(system engineers) want such a "system controler" microprocessor,
e.g., to better manage the PMU. The challenge is to get this idea
past the rest of Openmoko ;-)

We initially looked at several "small" microcontrollers, and settled
on the MSP430, but then the suggestion came up to try something that
doesn't need a separate toolchain, i.e., an ARM. Looking at various
recent ARM-based designs, it seems that this might be a viable
option, and it would emphasize the strength of our devices as a
developer-friendly platform.

AFAIK, there is no gcc for PIC18, making this architecture
unsuitable for our environment.

The general idea of integrating the debug board functionality into
the phone has been around for well over a year, but it's not trivial
to actually do this (space, cost, etc.). If we get an MPU with a
certain feature set, it seems natural to also let it handle JTAG.

- Werner

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