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emece67 · (This post was last modified: 05-04-2015 05:46 PM by emece67.)

I've also been thinking about the hw needed to build a "modern" RPN machine.

I'm now inclined towards ARM processors, my favorite now is the ATSAM4LS8AA. That's 512 kB flash, 64 kB RAM, Cortex-M4 architecture, serial and USB ports, AD and DA converters and with 1.5 uA current consumption in retention (aka continuous memory) mode. According to Atmel, it can run at 4 mA @ 48 MHz (sure it is higher with the required peripherals enabled). Does not have a "real" RTC but, apparently, it can be implemented in software (with a higher current than 1.5 uA, I suppose). It even has a true random number generator!

As a display I have seen these, being the 260x64 my sweet spot. There are transflective units not requiring backlight & with typical current consumptions about 500 uA, but with an sleep mode of only 1 uA.

With such current consumptions, 2 AAA cells will last for years!

Problem with the processor is that it only exists in SMT packages, I'm now studying if this can do the trick. There are plenty on youtube videos with people soldering QFN (even BGA) chips at home. A hot air soldering machine seems to help a lot and there are such machines at $60 in ebay.