Updating my WP-34s w/an available cable (Oct 2023)

[Peter Klein]

I recently updated my WP-34s (formerly an HP-30b) to v.3.3 3844, which I found in the complete WP-34s package currently on SourceForge.

Here's how I updated the calculator with a currently-available cable, and stuff I had lying around. It was "Quick-and-Dirty," but effective. Disclaimer: This is what worked for me. Your mileage may vary. Most of the information in this post is also available elsewhere on this forum. I believe I've contributed two new things: The specific cable used, which is available as of this writing (Oct 2023) and the easy fabrication of well-fitting connector pins out of a common household item.

Huge thanks to Paul, Walter, Marcus and the other contributors to the WP-34s project.

*** THE CABLE ***

I used the following cable, bought from Spark Fun Electronics in Colorado, USA:
https://www.sparkfun.com/products/12977

The cable is specifically USB to 3.3v TTL. Drivers, if needed for Win11, can be downloaded from the Documents tab on the product page. My PC runs Windows 11 Home Edition, but I didn't need the drivers.

The TTL end of the cable has four small pin socket connectors for TX Data, RX Data, VCC (3.3 v) and Ground. TXD and RXD will be connected, through resistors, to the serial port inside the calculator. VCC and Ground will be connected to the calculator's battery terminals.

   


*** DON'T MAKE MY MISTAKES ***

Initially, I had used a cable that turned out to be proprietary, and didn't work. I discovered this only after I had erased the earlier firmware. It also turns out that I didn't have to erase an older wp-34s firmware--the erase procedure is only needed when flashing the calculator for the first time, when it still contains the HP-30b firmware. In the manual, a section about vinyl overlays separates the flashing procedure from the update procedure, and I had stopped reading at that point.

*** CHEAP & CHEERFUL CONTACT PINS ***

I made contact pins for the calculator connector out of a "Jumbo" size paper clip. The clip's wire is about 1.2mm in diameter. It fits into the calculator's connector holes with only a little bit of wobble, so it's easy to hold the homemade pins in place while uploading to the calculator. (Note that standard sized paper clips are too small). I cut off about 17 mm from each end of the paper clip. Wire cutters don't make an absolutely flat cut, so I made sure that the flat "manufactured" end of each paper clip fragment was the end that would be inserted into the calculator connector for best contact.

I took two 100 ohm resistors and wound one lead around the cut end of each paper clip fragment, and soldered them at right angles. Note that others have used resistor values between 100 ohms and 1,000 ohms. (Click pictures to enlarge).

   

I soldered about 6 inches (150mm) of solid #24 wire to the other end of each resistor. The wire fit slightly loosely into the TXD and RXD cable pigtail connectors, so I curved the ends slightly for good contact. #22 wire would have been better.

I taped the pin connections up with vinyl electrical tape, color coding the ends. I covered the top of the pins with tape so I wouldn't cut my fingers holding them down while sending data to the calculator.

   

I also supplied power to the calculator right from the cable, which has pin connectors for VCC 3.3 volts and Ground. A short length of #22 brass wire fit snugly into the connectors, to which I connected alligator clips running to the calculator's battery terminals. (Note: If you're upgrading from an older version and you have data in the calculator you want saved, leave one battery installed).

   

I temporarily taped the pigtail connections with masking tape so they wouldn't accidentally pull apart or short-circuit.

   

The serial connector in the calculator has six recessed sockets for the Pogo pins on the official cable (which you can't get anymore). Open the battery compartment and set the calculator on its back with the battery terminals above the connector. The pin sockets are configured like this:

A B C
D E F

The TXD connection from the USB-TTL cable goes to socket A. The RXD connection goes to socket B. The ground connection is supplied by the negative battery terminal. If you need to erase the HP firmware, connect sockets C and D with a wire jumper, as shown on p. 150 of the manual.


*** TO FLASH OR UPGRADE ***

If you are flashing the calculator for the first time, follow the procedure on p. 147 of the manual (Appendix A). If you are updating the calculator to a later firmware, follow the procedure on p.152. Either way, connect the cable to the computer at the beginning of the procedure. To find out what COM port your cable is using, open Windows' Device Manager and click on the arrowhead next to "Ports (COM and LPT)."

You don't need to connect the serial cable to the calculator until just before the step where you click "Send File" in MySamBa. Put the TX and RX pins into sockets as indicated above. Hold them down with a finger and press "Send File." MySamBa reports on its progress each second. Continue to hold the pins down until MySamBa reports that it is done (It took me 23 seconds for calc-full.bin).

After uploading the firmware, reset the calculator and turn it on again. To reset, briefly insert a standard size paper clip into the little Reset hole above the serial connector.

Then, enjoy your new or rejuvenated WP-34s.