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RPN scientific calculator firmware for $13 calculator kit
10-21-2019, 04:43 AM (This post was last modified: 10-21-2019 04:48 AM by jklsadf.)
Post: #11
RE: RPN scientific calculator firmware for $13 calculator kit
The only thing I can think of that could cause LCD issues is either a connection issue or a low battery. Try checking all the solder connections again, and then reseating the LCD and also the processor in its socket. A low battery might also cause issues? I think it's unlikely though if you can actually see text, because the LCD requires 5V for good contrast, whereas the rest of the system can happily run at 3.3V. As Maximilian says, it could be a timing issue. The LCD uses a fairly standard Hitachi HD44780 clone IC controller chip, and some of these clones have slightly different timings. The firmware is supposed to poll the busy flag from the LCD, but sometimes people don't and instead just wait a fixed amount of time to simplify the firmware. (If I remember correctly, going to the first line first character takes more time than most operations.) I think a bad connection is still probably the most likely issue though...I don't remember having any trouble with the LCD back when I was using the original firmware.

The stcgal program to program the chip should work on most platforms where you can get Python and supporting libraries installed. I have tested that it works under Linux.

Thanks for making that new keyboard template. I've been meaning to, but so far haven't gotten around to change the key labels on my physical calculator. I'm curious what program you made it in, and if you have a higher resolution version?
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RE: RPN scientific calculator firmware for $13 calculator kit - jklsadf - 10-21-2019 04:43 AM

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