HP-41CL New Serial connection and port recovery.

[Diego Diaz]

Hi all,

I know that the HP-41CL is perfectly happy with just three ports available since all ROM PACs can be loaded by SW. Hence, 'sacrificing' port #1 to attach the serial connector is not a big deal.

Nevertheless, I'm a bit too picky when it comes to preserve cosmetics as original as possible.

A while ago, Bob Prosperi sent me a bunch of module housings without connectors. Eventually, some of the shells I use for my projects got broken while opening so these spares are very welcome. However, there are still quite a few that will be unused for the time being.

The idea of giving these empty shells a new life as a detachable serial (and CPLD port) extension for the HP-41CL seemed appealing to me.

First, a Flex PCB is placed into Port #2 top cover. Then a strip of 8 spring loaded contacts is inserted into the empty shell and protrudes from the top cover through a slot. Third, the Flex PCB is connected to the main CL board by means of 8 wires.

Ok, as usual, some pictures will help a lot here...
https://photos.app.goo.gl/63LfDLi2CLKPmUux9

https://photos.app.goo.gl/2qTua6MfTUJ1Tta28

https://photos.app.goo.gl/RKFr3DMKzGxEyDvx8

All this will probably end up just as a 'design exercise' without much interest, by I've enjoyed the process and wanted to share. :-)

Have a nice week!

Diego.

[PeterP]

Diego, this is not just a very interesting but potentially very useful design exercise. You might have been following the amazing work others like Meindert etc have been doing here with the Pico RP2040 (see e.g. here).

For that a "module type" connection is needed and one could use one of the 3D printed module shells available.

Meindert et al might be very interested in your design as the original "module fingers" are not that easily replicated. But your design or some small adjustment of it could be used potentially.

Where did you source the spring loaded contacts?

[Diego Diaz]

Hi Peter,

These are standard 2.54mm pitch spring loaded contacts.

I've got them from Aliexpress, but they're widely available elsewhere.

A few more pictures of this alternative connection:
https://photos.app.goo.gl/T1CDHubexLeK45o47

https://photos.app.goo.gl/ow4FuXQtw1w6sBLR6

https://photos.app.goo.gl/8PTjCM8AKLqvNwEZ7

https://photos.app.goo.gl/uNaQAeA8Go7yQ4Xi6

Cheers.

Diego.

Edit: Fixed image links.

[Johnboy]

Nice work Diego.

I can fix that case back for you :-)

Cheers,
John (Australia)

[cruff]

Google says that second batch of pictures don't exist and "that's all we know". Links private or something else?

[Diego Diaz]

Image links are now fixed.

Sorry about the inconveniences.

Best.

[Sylvain Cote]

Hello Diego,

You outdid yourself again, you came up with a way better design that I thought it was possible, impressive.

When are you planning to make this available ?
What will be the selling price ?

Best regards,

Sylvain

[MeindertKuipers]

Hi Diego,

This is really cool. Just curious what signals are on the connector, can you elaborate?

[Diego Diaz]

Hi Meindert,

This just takes out the 8 pins of the CP connector in the CL mainboard, and provides the 2.5mm jack for the serial interface.

Not rocket science. :-)

Cheers.

Diego.