[WP 34S] I finally bricked it :-(

[John Galt]

Walter, I do not know. I wish I did. I have only a suspicion that my mistake was permitting an interruption to Vcc during the flashing operation. I did that intentionally once before, but only once, to verify error detection and recovery in the event it were to occur unintentionally.

During that one, controlled test, a normal Erase function restored the ability to flash it again. It appears that was not to be the case this time.

Additional testing under controlled conditions may verify this suspicion, but if they do not duplicate the failure in a short amount of time a reasonably definitive conclusion may remain elusive.

Until then the only recommendation I have for others using the equipment and procedures I am using is to ensure any programming port connector ("pogo pin connector") they choose to fabricate on their own is both electrically and mechanically secure from failure as practicable.

The only similar failures I experienced in the past using flash memory (and the bootloader programming software involved - that's important!) were correlated to unreliable power or poor power regulation. None of them involved any HP products, and there were very few such failures. For certain critical systems I use triply redundant power supplies, so failure is essentially impossible.

One more quick fact to point out: the "flash box" I built and was using during the failure was both designed and intended for use by those who want an external power supply and status / Tx / Rx LEDs for whatever reason they may want those features. In the vast majority of cases in which only a firmware update is required, it is much easier and safer to use a simple connection with the calculator's own power, requiring only the external data signals supplied by whatever USB to serial device the user desires.