[wp34s] Permanently damaged machines when flashing

[emece67]

Today I've permanently damaged another (this is the second one) wp34s during flashing.

The symptoms are: during flashing (MySamba progress bar is moving) the machine hangs in some way, MySamba reports that it does not receive the ACK from the machine and, from now on, the machine is absolutely unresponsive.

I've tried even to flash it thru the JTAG port to no avail, the machine is, definitely, dead.

This is the second time it happens to me.

During the post-mortem analysis I've found that:

• Both machines have their cells at 2.9 V
• My USB to RS232 converter (a 3V3 one) sends levels up to 3.4 V thru the TXD line, this is 0.5 V above the battery voltage
• My DIY cable does not power the machine, during flashing the machine is powered from its batteries
  

and the SAM7L128 processor datasheet (that's the processor inside the hp20/30B) claims that the input voltage on any input cannot be greater than 0.3 V above the supply voltage.

Thus I suspect the combination of a slightly greater than expected output voltage on the RS232 port and the not so fresh batteries can be the culprit.

I cannot be sure this was the root cause, but I advise to use fresh batteries when flashing wp34s machines.

The HP cable, does power the machine besides the batteries?

Regards.