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RPN-duino
03-27-2017, 04:42 PM
Post: #61
RE: RPN-duino
That is a very good idea. Thank you.
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03-27-2017, 05:00 PM (This post was last modified: 03-27-2017 05:01 PM by BobVA.)
Post: #62
RE: RPN-duino
(03-27-2017 03:58 PM)Maximilian Hohmann Wrote:  Couldn't you show them on the display in some way, e.g. when the calculator has been idle for some time?

Regards
Max

Or perhaps call them up with the center push, if you can add some code to catch and discard any resultant inadvertant directional pushes? (Sort of like a keyboard debounce) Or maybe with a "long push" to a direction?

Nice project!!
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07-19-2017, 04:51 PM
Post: #63
RE: RPN-duino
After tidying up the built-from-parts joystick calculator, I decided to produce something similar but with a much higher specification. I have stretched the low cost Arduino Nano to its limit, with my code bumping against both RAM and flash memory ceilings. However, The Arm based Arduino Due is much more powerful and packs 96 KB RAM and 512 KB flash storage. It also has about a zillion I/O pins. The big deal with this device is that it supports true double precision floating point maths.

For the physical hardware I have gone for a 1.3 inch OLED - these can be had for what a 0.96 inch unit used to cost. I have conjoined two Farnell 4x4 keypads to give 32 keys. Some minor "chopping" was necessary to reduce their footprint. The makers have upped the spec. of these as the key tops are now of double-shot construction, which is not so useful to me. For example, on the last calculator I was able to scrape away at the letter "B" to leave a pretty decent decimal point! Also the back of the keypad is now heat staked rather than screwed on, which made moving the key tops around from phone to calculator layout a bit more difficult.

I have attached a picture of the Due based calculator in a fairly raw state, sans keyboard labels.

It is displaying the result for the tan(355/226) trig torture test. This makes me happy.


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07-19-2017, 05:26 PM
Post: #64
RE: RPN-duino
Good to see you back again in action. Thanks for sharing your latest design. Please, keep us posted about the progress :O)

Saludos Saluti Cordialement Cumprimentos MfG BR + + + + +
Luigi Vampa +
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07-19-2017, 06:12 PM
Post: #65
RE: RPN-duino
Those keypads look very similar to the one(s) I had but mine were 5x5 and the bottom row of buttons had clear removable keycaps so you could place your own labels. I wonder if those are still made.
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07-24-2017, 01:50 PM
Post: #66
RE: RPN-duino
The Due calculator has progressed. It is a bit of a brick since it is built around a Due board with header sockets and runs off a PP3 battery. A much lower profile device would have resulted from using a solderable Due PCB combined with a LiPo battery plus charge controller - that will be a project for the future.

Otherwise things have gone well. Compared to the regular Arduino, this thing goes like a rocket. It computes 170 factorial in the same subjective time that it takes to add 2 + 2 and the I2C connected display responds with no perceptible lag. The relatively huge RAM space allows for the reckless use of a variety of u8glib display driver fonts. With my previous designs, I had abandoned this convenient graphic device library and resorted to writing my own display driver code to avoid running out of RAM variable space.

Attached is a picture of the calculator in its alternate high precision one line display mode showing the answer to 170 factorial.

The only fly in the ointment is the documented hardware bug on the Arduino Due R3. From a cold start it runs the boot loader instead of your code and sits there doing nothing. A subsequent power cycle or hard reset is necessary to get your code running. There are hardware and firmware fixes for this, but right now I don't want to blow my board up. The problem was fixed on newer releases of the board.


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07-27-2017, 03:44 AM
Post: #67
RE: RPN-duino
That is so cool. Has both a retro and futuristic look to it. I see there is no "grads" for angles. In all my years of learning and teaching math I've never used grads. Does anyone use them?
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11-28-2017, 09:11 PM
Post: #68
RE: RPN-duino
nice job!
Reminds me of when, in 1976, I built my own apparatus to compare calculator and telephone keypad layouts for my first master's degree. I got two free calculators from Sinclair, kluged a 4x4 keypad (one of which had key layout and contacts changed). Built a 5v power supply and away I went. I believe I used an HP-45 for my data analysis.


.....Art Leyenberger


(10-16-2015 03:55 PM)Chasfield Wrote:  I have been busy with a home brew RPN calculator project based on the Arduino Nano mini board. The impulse to get going with it came from finding an Arduino starter kit that had been sitting unused since last Christmas, linked to the discovery that Rockwell once turned out four banger calculators with an easily detachable modular keyboard. I cannibalised a 20 key unit from a model 18R. These keyboards have a nice, almost HP48-like action and are perfect for adding custom key labels to. These old calcs are cheap on auction sites.

As the pictures show, I finished up with a fairly chunky device in a custom case. It features varnished pine trim, which I believe is a first for calculators!

The back-lit display is the ubiquitous and ridiculously cheap 2x16 character 1602 unit. And power comes from a PP3 battery, which should be good for about 20 hours use at 30 mA current draw. That isn't bad, given that the calculator has a real on/off switch. A reflective type LCD would double the battery life but I quite like the blue and white glow of the one used - easy on middle aged eyes as it is.

Calculating accuracy surpasses the Sinclair Scientific by a couple of decimal places but floating point maths is not a strong feature of regular low cost Arduino boards. At the moment, standard form number handling isn't programmed - big/small numbers with exponents display as 0. Digging the bits of them out of Arduino "float" type variables and doing something useful with them is a project in progress.
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11-28-2017, 09:40 PM
Post: #69
RE: RPN-duino
I like all your DIY approaches.
BTW, since I was a child, I have always had a "middle-aged sight" 8') I have always preferred bigger-than-usual fonts.

Saludos Saluti Cordialement Cumprimentos MfG BR + + + + +
Luigi Vampa +
Free42 BlackviewA7 '<3' I + + +
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