HP30b flashed with WP31 no longer responding

[mfleming]

Here's an update on the "bricked" calculator problem.

A bit of testing indicates the wee beastie might still be alive. I started by following the checklist in the troubleshooting section of the manual. I used a DVM to ring out the traces between the Tx/Rx connector pads and JP5 & JP6, and checked the traces between the Vcc/Gnd pads and the battery connectors. All good. For full measure, I checked the LCD display and its ribbon connection.

The MODE command output for the COM port after MySamBa was started was the same as shown in the manual. After doing a Send File, the baud rate changed from 1200 to 115200, which I assume is correct for the flash utility. No luck with getting the calculator updated though.

I then checked the state of the Tx/Rx lines under different conditions and compared them to a working WP 34S. When power is first applied, the serial pins are at 0 Volts. Pressing the On button causes the two lines to go high. The lines remain high when the WP 34S is turned off. Pressing Reset causes the lines to go low to about 0.10 Volts as opposed to a flat zero. Turning the unit On again causes the lines to return high.

Since both calculators respond identically to power-on and reset conditions, I would assume there's something still ticking in the problem unit. If I had access to the lower address lines I could use a scope or logic analyzer probe to see if there is any activity. Perhaps the first successful transfer left a corrupt program image and that somehow interferes with the serial port, or else just causes the processor to halt.

Looks like the next step will be to attempt a JTAG connection. I'll update afterwards with the setup used and steps taken.

Stay tuned!
~ Mark