Post AQoR0UEhZ2cB5dksT2 by gbrnt@hackers.town
(DIR) More posts by gbrnt@hackers.town
(DIR) Post #AQoR0NjziIUEwfLGls by gbrnt@hackers.town
2022-10-11T20:31:12Z
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Electro-sax project post:One of my long-running projects is a MIDI-powered saxophone I'm calling the "electro-sax". The aim is to make something that's fun to play and feels fairly close to a real sax, so I can practice quietly.The full thread about this is back on my old account @gbrnt@mastodon.technology but unfortunately that will be gone soon. I'll try and briefly summarise the project here before I carry on.Current versionThe current version uses custom-made switches based around conductive silicone making contact against a PCB. It uses a pressure sensor to detect blowing and I've made some progress on a bite sensor using a force sensitive resistor. It feels good to play!Previous iterationsFirst test to see if I could get kinda close with no effort. Used MX-style keyboard switches for keys and a homemade breath sensor made from cardboard, a plastic bottle top, a balloon, an IR LED and a photodiode. Surprisingly good to play, but the keys didn't feel right because their actuation point was way too early.Capacitive touch version with adjustable 3D printed breath sensor. Big breath sensor improvement but the capacitive keys were horribly non-tactile to play.Microswitched based version - didn't go far with this at all because all the clicking was horrendous.Hybrid capacitive+mechanical switched version. This is where it gets good. You press on a lever that resists your finger, but your movement is sensed capacitively. Was very tedious to calibrate every time you wanted to use it (and after readings drifted a bit).Current version - conductive switches, off-the-shelf pressure sensor for breath sensor. The palm keys still don't feel quite right as they actuate too early.
(DIR) Post #AQoR0OT10uV1CIPDwe by gbrnt@hackers.town
2022-10-11T20:39:15Z
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@gbrnt@mastodon.technology Some photos of the previous iterations for context - I meant to put these in the first post.
(DIR) Post #AQoR0OyZ7bjim9AQ7c by gbrnt@hackers.town
2022-10-11T20:48:45Z
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@gbrnt@mastodon.technology Aaand my last update was about prototype 5, which works enough to play now!I got a resin printer before starting this one, so the keys can be funky shapes without worrying so much about printability. The wiring inside is still a mess, but that gets hidden so it doesn't really exist.The pressure sensor I'm using for the breath sensor is kind of expensive (£14) but it'll be worth it if it lasts a while. I find it holds calibration better than my homemade pressure sensors, although it's still not perfect.
(DIR) Post #AQoR0PYixAeyaI5ITw by gbrnt@hackers.town
2022-10-11T20:52:15Z
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@gbrnt@mastodon.technology At the moment I'm working on a PCB to put in the next prototype. It's based around an RP2040 (so I'll probably rewrite my software in Python) and has a nice USB-C port, plus breakouts for a few extra pins (i2c for an OLED maybe?).This board has loads of space but I'm not good in terms of thinking in 2 layers, so it's taking me a while to sort out. The connectors are on the bottom side facing inwards, which hopefully won't prove to be a mistake.
(DIR) Post #AQoR0QBicBqsXEKRGK by gbrnt@hackers.town
2022-10-23T21:20:20Z
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@gbrnt@mastodon.technology The electro-sax PCB is nearly done! The routing is not neat but at least the top looks mostly ok. I've gone a bit overboard with ground vias but I don't think they'll hurt anything.This is my first time using KiBuzzard for the fancy silkscreen and I really like it!
(DIR) Post #AQoR0Qdiw4Flw5Qnui by gbrnt@hackers.town
2022-12-11T16:36:59Z
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I decided the electro-sax PCB wasn't gonna get any more done and released it - hopefully it'll arrive around the end of the year and I'll be able to try it out!
(DIR) Post #AQoR0RJYQXiK1p0D7A by gbrnt@hackers.town
2022-12-19T21:47:15Z
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Yessss they arrived! I couldn't resist populating one of the electro-sax PCBs even though I'm missing one capacitor value and one connector. The pasting went pretty well, although I did get some bridges on the QFN chip. First time I've done a QFN and the bridges appeared to go with a quick wipe from a soldering iron.My multimeter's battery died so I had to improvise by hooking it up to a bench power supply. It worked and as far as I can tell so far everything is soldered ok!
(DIR) Post #AQoR0RrwMhDfkT5fiC by gbrnt@hackers.town
2022-12-20T20:33:45Z
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Hmmm, the RP2040 UF2 bootloader works just fine - it shows up as a drive and I can put files onto it. When it reboots into operational mode it doesn't obviously do anything. e.g. the USB "hello world" example doesn't show up as a serial port. Micropython didn't work out of the box but the image was made for an actual Pi Pico so I'm not particularly surprised.I need to write a test program using the SDK to try just flashing an LED, and hopefully that'll get me on my way.
(DIR) Post #AQoR0SbJdzW21CJuRE by gbrnt@hackers.town
2022-12-20T21:06:33Z
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Does picotool info showing program information mean that the QSPI flash is working, or is that info stored on the #rp2040 ? I may just not be putting the pin number in correctly (or my LEDs could be the wrong way round!), but this isn't working at the moment.
(DIR) Post #AQoR0TCXPbI1sdjdSK by gbrnt@hackers.town
2022-12-20T21:09:22Z
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Actually picotool verify verifies that my blink sketch is correctly flashed - there's no way that the QSPI isn't working then, is there? If my multimeter wasn't dodgy (it wasn't just a dead battery) I'd check some pins. Maybe it's time to bring out that cheap Hantek scope.
(DIR) Post #AQoR0TjVR1f3Wt9xqK by gbrnt@hackers.town
2022-12-20T21:20:00Z
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I think this person has the same problem as me: https://forums.raspberrypi.com/viewtopic.php?t=313306The RP2040 is trying to access the QSPI flash as if it's a Winbond one when it isn't (because I couldn't get them). So I just need to change it to use a more generic boot stage 2.
(DIR) Post #AQoR0UEhZ2cB5dksT2 by gbrnt@hackers.town
2022-12-20T22:46:56Z
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Errr tusky ate my post but the solution suggested in the thread did work for me, and now I have blinky lights!
(DIR) Post #AQoR0Ui7ne9OYtWNKS by gbrnt@hackers.town
2022-12-20T22:48:02Z
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IT LIVES!
(DIR) Post #AQoR0VCFzcFm4LcRIO by Polychrome@poly.cybre.city
2022-12-20T22:55:29.966600Z
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@gbrnt woo! :blobcattoot: