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Butterfly keyboard on 1995 IBM ThinkPad 701c. 0:19 video:
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More: https://en.wikipedia.org/wiki/IBM_Th...erfly_keyboard
Previously:
https://www.homemadetools.net/forum/...761#post129048
I remember those; a prof at work had one. It lasted about a year or so before the folding mechanism broke, iirc.
The single biggest breakthrough in reliable keyboard/keypad functioning, was the development of the scanning keyboard, by Cherry Keyboard co. No more holding your mouth just right, to avoid getting a short line of repeated characters, due to key bounce. No more trying to time a sampling strobe, to get a 'clean read.' Keypad switches were free to bounce all they wanted, once the matrix latches set, and the comparative counter took off running. Amazing how such an obvious solution – after the fact – eliminated the heartache of keyboard entry, for an entire industry.
I changed my method of scanning on small x by y keyboards to a static watch long ago (like in 8051 time) to save power and realtime. Drive either all the rows or columns low and set the other half as inputs (with pullups, of course). Enable interrupt on input change. Wait.
When someone presses a key, the interrupt routine swaps x & y input vs output, calculates and reports the key pressed, THEN starts the debounce timer to rearm interrupt. No scanning so no EMI and no wasted power.
There's a nice chip, the TM1637 that scans a keyboard AND drives 6 LED 7 segment displays at the same time. You talk to it with a modified I2C (to avoid royalties).
The chip is often found driving a cheap LED display with no keyboard (about $1 on eBay)
Attachment 30104
I did not know.
