NEW: HP 15C Collectors Edition

[Eric Rechlin]

(11-02-2023 01:42 AM)dmh Wrote:  Has the new cable been documented anywhere? How to build from scratch or modify the LE cable?

If you are willing to permanently sacrifice an LE (20b/30b) cable, here are the steps:

1. Open the section with buttons (two #0 Phillips screws), desolder the serial cable, slide off the strain relief to reuse, cut a USB cable, slide the strain relief on the USB cable, and solder the USB cable on. Green from USB goes to TXD, white to RXD, and black to GND2. Red is unused.


2. Cut the two traces from TXD and RXD to the chip using a razor blade or other sharp object, with two separate cuts (see the photo, above and below the left hole). Then make a single long cut to the lower left of the right hole to cut all three traces there (DTXD, DRXD, and VCC). The VCC trace is thicker than the other two. Cutting these is to bypass the level shifter chip.


3. Now you need to solder two jumper wires. Solder one from RXD to DRXD (the top via on the left to the upper-middle via on the right) and one from TXD to DTXD (the bottom via on the left to the lower-middle via on the right).


4. Reassemble (be careful with your wire routing so they don't get squished by the posts when screwing the box back together) and it's all done:


The effective wiring is as follows: