As a calculator enthusiast, I could not avoid buying the new kid on the block: the smallish DM-15cc from www.rpn-calc.ch
At the very low price of 50 CHF, it is a luxuty one can afford. I bought two units - one to keep original and another to experiment with.
It is based on the original HP15c firmware, running on a nut processor emulation on a LPC1114 ARM processor. The unit chosen should give a decent battery life - let's see. (Not that I am unhappy in any way with the HP15c Limited Edition battery life - after 6 months of heavy use (but not running long programs) it is still using the inital battery set)
The unit is really minimal: see pictures comparing it with the original 15c and the new Limited Edition. I can imagine that it is too small for some fingers, but not for mine.
The keyboard has small domes. Of the two units that I have, on one of them all keys register when they click; on the other, some rows require higher presurre to register. The key feel is excellent, while no one would exchange his old HP for this one for the rest of your life.
The colours chosen mimic more the original than the new. The new is all black, while the original had black keys and dark brown for the surface. This clone has a lighter shade of brown than the original but it makes clear what is a key and what's not.
The keyboard will resist grease and dirt. The unit is not water-proof, though: water can come through the sides since it is not sealed. Here there is a picture of the side. Some dust can make it to the screen due to the same fact.
The calculator can be easily opened and cleaned, though. This is clearly a calculator for the Do-it-yourselver.
The version I have is the so-called version 2. There is a third version coming, that will have an aluminium back and better isolation. I will order another - probably in HP16c form. This version comes with a fiber pouch, but sometimes there is a problem with static electricity, whereas the calculator resets. I have read about it in forums and have experienced myself just once. I guess that it has something to do with the screws in the back. It seems that it will be solved with the newer back in version 3. another short term alternative is to use a different pouch or isolate the screws.
The screen has low visibility under heavy light. This picture was taken on a very sunny floor. but the calculator was switched on, showing "PI". Here below you will see the original on the exact same condition, as well as the LE:
(See the brownish tint to the keyboard surface? Guess you never noticed until you saw the Limited Edition version)
The light conditons make all the more apparent any dust on the surfaces.
The better visibility comes with the original one; second comes the LE and distant third the DM-15cc
On normal conditions, the numbers are much bigger on the DM-15cc. It has two dispay modes: one with rounded digits and another with square ones (mimicking old led displays)
Blog ideas are getting accumulated, and I owe a lot of posts about getting deep into other products. Again, I need to come back to this one. I will put in all my programs and see how it compares with the original, when it comes to real world usability. As well, I will introduce in one of my samples the other firmwares, the ones sporting more memory.
While I started my professional life as a programmer, I am in no way expert on low level programming. I would like to be able to apply the patched firmwares to one of my HP15c LEs and have a supercalculator. I know it can be made, and eventually I will be able to do it - either myself or somebody else.