This week's Desk of Ladyada is a little light on hardware, as we spent some of the weekend outside and the rest on some software hacking! We used to get very nice pinout diagrams made for our boards by a fellow named Pighixxx. They ended up doing a crowdfunding project that didn't work out and they stopped replying to emails. We like having pinout diagrams but also know that if it's too hard, we won't keep up. Check out Bill Binko's video for a manual technique https://blog.adafruit.com/2019/07/11/automating-the-making-of-beautiful-pinout-diagrams-for-microcontroller-boards-documentation-at_makers/
Much like our Fritzing tool which can generate 99%-ready fritzing objects, having an automated way is best! We looked at the Sparkfun Graphical Datasheet tool (https://github.com/sparkfun/Graphical_Datasheets) and its a step in the right direction - but we didn't want to have to create a CSV for each board because I am very lazy!
So we're experimenting with using the Fritzing file, circuitpython pin file, and a single chip-pinout spreadsheet to help us get something 'good enough' even if it isn't as beautiful as the Pighixxx ones. I'll talk about some of the tools we ended up using and why we still need a human to wrap it up.
We also made the first draft of an RP2040-powered 3x4 macro pad with rotary encoder and OLED that we'll show off.
The Great Search - Alternatives to TL074 Op-Amps!
https://www.digikey.com/short/85mv3mrm
We noticed a few synth-makers getting worried about not being about to source TL074 quad op-amps!
https://twitter.com/theavalkyrie/status/1381800012162666497
https://twitter.com/otdispace/status/1382920010042081283
We thought we'd spend this Great Search looking at the TL074 - why its so great and what to look for in an alternative. We asked 'guest' - the co-designer of the x0xb0x to drop some knowledge on us:
the 074 is pretty much the toyota corolla of opamps. its not the best at anything in particular, but pretty good at everything. its the second cheapest opamp out there, comes in dip and soic, has relatively low current consumption, low distortion, and reasonable bandwidth and slew rate. the noise is ok-ish low, but the thing that really makes it an all around performer is the low bias current. its down in the pA range, which means you can use it for S/H or VCO,VCF, etc that require a range of currents down to the nAs. a lot of people used the LM358 because it is the cheapest opamp, but it has high bias current. the 074 can also handle high voltage rails which helps with SNR. it was designed for audio use, and was one of the first real mass market opamps back in the late 70s (if i recall correctly). the 741 was the first, and this was meant as an improvement over that. the 074 and 084 were made at the same time, and 074s were selected for lower noise, better distortion, and lower offset voltage, and then marketed at the audio market. the 084 was sold to everyone else.
Who doesn't love the TL074? Apparently a lot of people - so let's look at a backup-option. It may not be as cheap/good but maybe it'll be in stock!
#adafruit #digikey #thegreatsearch
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