Supercon Badge Reads A “Punch” Card

This year’s Hackaday Supercon, the first considering that 2019 thanks to the pandemic, was a extremely identical affair to those people of the earlier. Pretty much every hardware-oriented hacker event has its personal tailor made digital badge, and Supercon was no distinct. This year’s badge is a simulation platform for a hypothetical 4-little bit CPU created by our individual [Voja Antonic], and introduced a actual obstacle for some of the attendees who experienced hardly ever touched device code through their formative several years. The problem set was to occur up with the most attention-grabbing hack for the badge, so collaborators [Ben Hencke] and [Zach Fredin] established about nailing the ‘expandr’ category of the level of competition with their optical punched card reader bolt-on.

Peripheral connectivity is somewhat confined. The concept was to construct a bolt-on board with its have neighborhood processing — making use of a PixelBlaze board [Ben] brought alongside — to deal with all the scanning facts. Then, as soon as the method on the card was read through, dump the total thing in excess of to the badge CPU by way of its serial interface. With no obtain to theirPrinted paper faux punch card showing read LEDs and an array of set and reset bits of the encoding typical services back residence, [Ben] and [Zach] naturally experienced to improvise with whatever they experienced with them, and what ever could be scrounged off other badges or other components lying all over.

A single large issue was that most people today never commonly have photodiodes with them, but fortunately they remembered that an LED can be used as a photodiode when reverse-biased properly. Feeding the signal developed in excess of a one Meg resistance, into a transconductance amplifier courtesy of a donated LM358 there was more than enough variation for the STM32 ADC to reliably detect the difference between unfilled and crammed verify-boxes on the crammed-in program cards.

The CPU needed 12-bit opcodes, which obviously implies 12 photodiodes and 12 LEDs to browse just about every term. The PixelBlaze board does not have this a lot of analog inputs. A very simple trick was alternatively of getting discrete inputs, all 12 photodiodes had been wired in parallel and fed into a solitary enter amplifier. To differentiate the diverse bits, the illumination LEDs as a substitute have been charlieplexed, consequently providing the individual bits as a sequence of values into the ADC, for subsequent de-serialising. The demonstration movie demonstrates that it is effective, with a system loaded from a card and kicked into procedure manually. This sort of enjoyable!

Punch playing cards generally have a hole as a result of them and can be read through mechanically, and are a wonderful way to configure testers like this attention-grabbing vacuum valve tester we coated a brief although again.

Luis Robinson

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