[wp34s] Permanently damaged machines when flashing

[Perre52]

The maximum supply voltage Vd of the Atmel processor is 3.6V.
However the input data pins can have a Vd + 0.3 V. That's 3.9V without any damage to the processor.
I flashed mine yesterday with a BV101-4 USB to serial interface cable.
The max voltage on the Tx pin of this interface is 3.85V.

I did fry a calculator but not by programming the calculator. I used a power supply as a voltage source for my calculator during programming. And the voltage on this supply was 9.0V ! I noticed the fault but it was to late.

Try measuring the current when the calculator is on. It should be around 5 mA.
If you measure this value chances are great that your calculator isn't dead but just "sleeping."
This is also the reason that I use a power supply instead of the batteries. I can measure the current and know if my calculator is on (5mA) or off (0mA) during programming.

The HP programming cable uses a ADM3202 IC from Analog Devices.
This device draws its current from the calculator batteries.
You can find more about this cable here: http://hhuc.us/2008/Interfacing%20to%20t...b%20V3.pdf