Do we know what drove the open design of the 20b/30b calculators? AFAICT, no other calculator since then has the ability to refashion the firmware. On the 30b they went as far as provide pads for not just the JTAG port but also for the digital and analog io ports of the chip. I really wonder what they were thinking (in a good sense of course!).
I don't think they had WP 34S in mind. ;)
The 20b was the first of a line of calculators using the Atmel ARM chip. The open design must have helped HP in the software and hardware development process. They may have even had some re-purposing in mind, be it for educational use (the 20b has been used for this by the University of Columbia), or for some vertical applications (equipment control, sales forces).
Cyrille basically. The thinking was:
1. It was hoped it could be a platform for re-purposing (embedded systems course in education for example).
2. Opens possibility for in field updates, or at various hp locations (this was a long shot. Unfortunately it could never happened to complexity of process and non standard cables/connection). Unable to do something like USB since that added significant cost - the exposed pads did not.
3. Allows a single HW version instead of special ones for development.
4. Ability to run automated testing on HW including production units.
And yes, any of the atmel chipped units have the ability to re-flash. The 20/30b is the only with the jtag though. Mainly it was removed because later it wasn't really needed at all for development since things were already running.
TW
Edited: 7 Sept 2013, 10:25 a.m.