Calculator blog

I have seen in Facebook several opinions about the HP15c CE and I would like to comment on them.

• The HP15c CE and HP15c LE are not "the same calculator": there is a different processor, more advanced and with less consumption. Also the keyboard quality is superior. Battery life is at least 6 times better on the CE than the LE. My first CE is still running with the first set of batteries despite being my main calculator. 
• The HP15c CE is reallistically firmware upgradeable. By "reallistically" I mean that there is a method and a non-DIY cable available here. Also, the HP15c CE is very difficult to brick: I have modified with new firmware more than 200 units with no failure whatsoever. 
• All the known bugs of the HP15c LE have been fixed in the first CE firmware.
• The CE comes with more memory: 98 registers instead of 65 - and there is a hidden method to get to 194. This opens up a lot of application possiblities, regarding long programs and/or heavy matrices (you can have, for example, 3 8x8 matrices simultaneously!).
• The CE comes also with a hidden, non-supported HP16c "clone" inside. To make use of this clone there is an available silicone overlay with the HP16c key set up. The original firmware has a bug, but this is easily solvable with the programming cable. Below a calculator running the HP16c clone without the bug.
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• The USB connection (albeit with a non-standard plug, solved by the cable) can allow backing up and restoring memory (increasingly important with the extended registers) and interfacing with external software HP15c simulators, with just a firmware change. This also opens the possibility of software pacs (Finance, EE, Mechanical engineering, Algebra, etc.)

Hopefully not too far in the future...

As you know, your HP15c CE has a USB connection in a 6-POGO pin connector in the batterty bay. This connection can be used with a cable, and so far has served to fix the firmware of the machine to fix several bugs.

Now we are testing its use to back up and restore the calculator memory , and also to interface with external software, to modify programs and document them. It will be fantastic to be able to do so - which was not a possibility when you bought the calculator!! Also: no more costs involved, aside from the interfacing cable.

Hi, 

I tried to work on the keyboard of a HP15c CE. I opened it, taking out the 5 screws (do not forget the one beside the battery!). Here is what can be seen inside:

If you are DIY inclined, you could add a standard nano-USB on the left side of the calculator (which is on the right side in the picture). Beware: it requires drilling your precious unit!

On the other hand, no way to go into the keyboard: many permanente fixings, risking to break the calculator.

I have been using the Schwanheimer Industriekleber 100 glue already for some time. When properly using (making generous use of the primer on both sides) it is the best glue I have used for calculator repair. Better and thinner than E6000; no comparison with E6000+; and miles ahead than other cyanoacrylates. I think the primer makes all the difference.

You can read my initial feelings on this glue here: http://www.thecalculatorstore.com/Calculator-blog/A-new-glue-for-HP-repairs

So much so that when the glue is finished (the primer is not, yet), I have gone to their website and bought the whole pack: it comes in a portable plastic bag. I am looking forward to finish all the repairs that I have in front of me, and I will report later. It includes an accelerator, a filler, a mechanizable patty and a solvent too. 

The enhancements I foresee for the HP15c have to do with the cable and firmware posibilities:

- Backup and restore user memory

- Some kind of memory manipulation of the user memory file, so that it can be used in other software like Thorsten Manz's fantastic HP15c. 

Both things together can create an ecosystem for the HP15c. So far, entering a program was cumbersone and had to be done each time. With backup and resotre, + memory editing outside of the calculator, you will be able to exchange software between users - and development and use will skyrocket compared with having to enter any single program yourself. 

Let's see. I have heard that there are already firmware prototypes to do that.

I have already had 3 customers that have purchased a HP12c (NOT HP15c CE !!) + the programming cable + HP16c overlay. 

You can guess what the plan is: to get a much cheaper HP16c in addition to their HP15c CE (which all three purchased before, with the newest firmware already fixing the DEC bug in HP16c.

Also, around 300 customers have purchased the cable to fix their firmware. While this is the original reason, these customers will profit of the cable in ways that we can only imagine. So far, when you rewrite the calculator firmware, you need to reset it and all programs and data previously introduced are lost.

However, the Atmel processor has other USB modes that can be used to back up the user memory, and restore it if needed. This opens the possibility for multiple configurations, and even HP15c "application pacs"

Finally we received the cables (just 300 units of the 1000 ordered- the rest after Chinese new year), and we are shipping them to customers already. Hold on- yours is about to be sent if it hasn't yet.

On the other hand, we have created some pages with information on the use of the cable. We have just focused on the current use, but there will be more! So I would also consider obtaining a 3D printed back door - to avoid having to carry a screwdriver with you!

We finally have a DHL delivery date for the cables ! We are receiving them this Thursday. We have already prepared many packages and documents to be able to send as many as we can immediately.

The cables have CE certification. I will post it here when I get the original copies of it.

Here are some pictures of the complete cable:

Hopefully sent to customers by the end of the week.

There will be some sort of compensation for the delay to all.