Another stupid flashing cable question HP-30b / HP-15C CE

[Eric Rechlin]

(09-19-2024 10:10 AM)rprosperi Wrote:  

(09-18-2024 01:01 PM)Maximilian Hohmann Wrote:  Hello,

I am desparately searching for my old flashing cable needed to convert

Max - Nothing to be desperate about, but I get it... I'm the same way. But no need to worry, the original will turn up shortly after you find or make a replacement.

Also, Eric Rechlin posted clear steps with photos about how to convert an "LE cable" to a "15c CE cable" so you can probably use it to do the opposite:
https://www.hpmuseum.org/forum/thread-19...#pid179488

Doing the opposite is a bit more involved since you need to add a level shifter somehow. There are basically two ways to do it. One is to convert the TTL-voltage out of the USB connector to RS-232 serial, and then use a RS-232 to USB adapter to plug that into your PC. The other, simpler way would be to convert the TTL serial directly to USB.

For the first, you'd need to get a level shifter like this:

https://www.adafruit.com/product/5988

Then get a USB extension cable, cut off the male end, and solder the wires to the above level shifter. You might need to solder one of the pins from the DE9 connector to VCC as well to provide power. Then plug the female end into the 15c CE cable, and the serial connector of the above level shifter into a USB-to-serial adapter, and then plug the USB-to-serial adapter into your computer. But if you don't already have a USB-to-serial adapter then that would be an added expense, so the second approach would be cheaper.

For the second, you'd want a USB to UART adapter like this:

https://www.amazon.com/dp/B07WX2DSVB

Then get a USB extension cable, cut off the male end, and solder the wires to the above adapter (just TX, RX, and ground), and plug your 15c cable into the female end of the cable. There are cheaper USB to UART adapters (like half the price) if you shop around but I prefer the FTDI-brand chip ones which tend to cost more.

I've never done this but in theory either of these approaches should work, and I know who someone did the second approach and it worked.

If you don't have a USB extension cable lying around to sacrifice, any cheap one would do, like this one:

https://www.amazon.com/dp/B002KKZAIU