Finishing up on the topic of CMOS bus logic I am going to show a couple of families with unique properties that may come in handy one day.
High Voltage Tolerant Family: AHC/AHCT
First up is a CMOS logic family AHC/AHCT that has one of the protection diodes on the input removed. This allows a 5V input voltage to be applied to a device powered by 3.3V so that I don’t have to add a gate just for the translation. Any time I can translate and do it without any additional gate delays I am a happy engineer.
Of course the example above works in a single direction and bidirectional does start to get more complicated. Using a bidirectional buffer such as a 74AHCT245 will work for TTL translation when going from 3.3V back to 5V providing there is a direction control signal present.
[Rue Mohr] found a very cheap TFT display on an Arduino shield. The chip for the display was an SPF5408, a chip that isn’t supported by the most common libraries. He eventually got it to work after emailing the seller, getting some libraries, and renaming and moving a bunch of stuff. If you have one of these displays, [Rue] just saved you a bunch of time.
The ancient computers of yesteryear had hardware that’s hard to conceive of today; who would want a synthesizer on a chip when every computer made in the last 15 years has enough horsepower to synthesize sounds in software and output everything with CD quality audio? [Brian Peters] loves these old synth chips and decided to make them all work with a modern microcontroller.
[Brian] connected all these chips up with Teensy 2.0 microcontrollers, and with the right software, was able to control these via MIDI. It’s a great way to listen to chiptunes the way they’re meant to be heard. You can check out some sound samples in the videos below.
It’s totally excellent when a simple concept results in something inspiring and fun. [Rich Decibel]’s Kequencer is a good example, starting off as many projects do: “I had an idea the other day and I couldn’t decide if it was good or not so I just built it to find out.” Be still our hackable hearts!
[Rich] built this sleek little sequencer from scratch and while the design may not seem very novel to begin with–eight square wave oscillators with on/off switches and pitch knobs, played in sequence–but the beauty of it is in the nuances of interaction and the potential for further hacking. From watching the video you can see how the controls can be used in very interesting ways to create and mutate adorable chippy tone patterns. Check it out after the crossfade.
We’ve all known the MSP430s under the Launchpad are designed to be low power, but who wants to bet how long the chip can last on only 20F worth of capacitors? A couple of hours? A day at max? [Kenneth Finnegan] setup a MSP430 with supercaps to find out. To make sure the chip is actually running, [Kenneth] programmed it to count from 0 to 9 over a period of 10 seconds, and then reset. To get it ultra low power, the chip is in sleep mode most of the time, and a raw low current LCD is used to display the output. While [Kenneth] simply checks the chip every few hours to see if it’s still counting, a setup much like the Flash Destroyer, tracking a clock and then storing the current value would get a more exact time of death. Either way, it’s been over 3 weeks…and still counting. Video after the rift.
[James] is interested in reverse engineering some integrated circuits. One of the biggest hurdles in this process has always been just getting to the guts of the chip. He used acetone to dissolve the plastic case but had trouble getting through the epoxy blob. Commonly, the epoxy is soaked in nitric acid for a few minutes but [James] didn’t have access to that chemical. Instead he popped into the local music store and picked up some rosin (used to make violin bows sticky enough to grab the strings of the instrument). After boiling down the rock-hard rosin and the chip for 20 minutes, he got a clean and relatively undamaged semiconductor that he can easily peer into.
The streamlined interface, reminiscent of Google, returns just the essential information much quicker than rummaging through PDF datasheets (which can also be downloaded there if you need them). And the output, being based on simple text and CSS, renders quite well on any device, even a dinky smartphone screen.
Site developer [Matt Sarnoff] summarizes and calls upon the hacking community to help expand the database:
“The goal of my site isn’t to be some comprehensive database like Octopart; just a quick reference for the chips most commonly used by hobbyists. However, entries still have to be copied in manually. If anyone’s interested in adding their favorite chips, they can request a free account and use the (very primitive at this point) part editor. Submissions are currently moderated, since this is an alpha-stage project.”