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Someone asked how play multiple simultaneous CD-quality WAVs from an SD card to I2S DAC on ESP32 in CircuitPython. Turns out: possible! Can get a bit glitchy if doing USB stuff tho https://www.youtube.com/watch?v=97OA6L9PLCg
code: https://github.com/todbot/circuitpython-tricks/blob/main/larger-tricks/wavmix_s2mini_i2s_sd.py
#CircuitPython #i2s #esp32 -
Pico Touch Board Audio
I wanted to go back to my Pico Touch Board PCB Design and see if there was a way to make it more stand-alone. The original design was to make it a MIDI controller, but that isn’t the only option.
https://makertube.net/w/tADSyrPrUdR1mx7yKRXZTC
Warning! I strongly recommend using old or second hand equipment for your experiments. I am not responsible for any damage to expensive instruments!
These are the key Arduino tutorials for the main concepts used in this project:
If you are new to microcontrollers, see the Getting Started pages.
Parts list
- Pico Touch Board PCB – built
- Resistors: 1x 220Ω, 1x 1K
- Capacitor: 1x 100nF ceramic, 1x 22uF electrolytic
- Breadboard and jumper wires
The Circuit
Most of the GPIO are linked out to the touch pads, but the three analog inputs are still available. They are added on to the header on the right hand side of the board at the top, so we can use one of these as an audio output.
Initially, I thought of connecting it to an 8Ω speaker. If I was using an Arduino then I’d use a 220Ω resistor in series to limit the current to less than 20mA. But as I’m using a Pico, the maximum current has to be a lot less. I seem to recall it is a little complicated, and there are some options, but I have a figure of around 4mA that I tend to work to. It is also running at 3.3V, which means that it would need an in series resistor of 3.3 / 0.004 = 825Ω. This would work, but the speaker will be really quiet!
So I ditched that idea (there is a software reason too, but I’ll talk about that in a moment) and went straight to a PWM output with a low-pass filter to try to give me some vaguely useful as a line-out signal.
I’ve not done the calculations, but instead went a bit “hand-wavy”, combing a 1K and 220Ω resistor to drop the voltage, along with a 100nF capacitor. I’ve also added a 22uF capacitor to remove the DC bias.
That seems to give me something useful, but as you can see from the trace below of a square wave PWM output, there is a lot of room for improvement!
Update
Ok, so going back and doing this semi-properly as per my notes from Arduino PWM Output Filter Circuit, I can see that the 1K and 220Ω resistors can be treated as a 180Ω equivalent (take them as two in parallel) for the filter circuit, which means a cut-off of around 8kHz which ought to be pretty good….
But reducing a 3V3 signal to around 20% leaves for quite a low level of audio – around 660mV peak to peak. It would probably be better to aim for a reduction of around a half.
Using a 1K and 500Ω resistor would be an equivalent resistance of 333Ω, so putting that into a low pass filter calculator gives a cut-off frequency of around 5kHz for a 100nF capacitor.
Weirdly the only thing that really seems to improve things is to raise that capacitor value to 1uF. My calculation would suggest a cut-off frequency of around 480Hz which is pretty small for an audio signal. But it seems to work.
The PWM frequency I was seeing was coming in at around 120kHz so should be plenty high enough to get filtered out. In the Circuitpython code, it is apparently chosen to support the number of bits required at the base clock frequency whilst being inaudible. For the RP2040 running at 125MHz, and with the chosen 10 bit resolution (more here) this is:
- 125,000,000 / 1024 = 122,070 Hz
A 5kHz (or even 8kHz) cut-off I thought ought to be fine, but Davide Bucci on Mastodon explained for me:
“120kHz is 25 times 4.7kHz, that is about 1.4 decades and with a first-order filter you have a tad less than 30dB of attenuation, that is not a lot. A signal at 3.3V peak to peak at 120kHz becomes about 100 mV on the output after the filter.”
So switching to 1uF, as Davide explains: “if you put 1µF, you are indeed filtering a decade lower, therefore you gain 20dB in the attenuation and the 100mV become 10mV, much less noticeable.”
The alternative is to repeat the 1K+100nF stage and add a second order filter which also seems to work pretty well.
The final circuit that works fine for me at present, will be on of the following.
The first is less components but assumes that the frequencies won’t go much about ~1KHz or so. That is ok for my current setup but would limit the audio range a fair bit.
This is the output of the two-stage filter. It is so much better!
The Code
I wanted to stick with Circuitpython, so my initial thought was to use simpleio.tone() to generate a tone based on a frequency from an IO pin. However, this has the problem that the code is blocking whilst the tone is playing which isn’t very useful.
Instead I went straight to synthio. It turns out that using synthio was actually a lot easier than the “simple” simpleio…
Here is the basic code to generate an ASR-shaped square wave on a PWM audio output on GPIO 28 based on the touch pads as input.
import board
import touchio
import synthio
import audiopwmio
from adafruit_debouncer import Debouncer, Button
audio = audiopwmio.PWMAudioOut(board.GP28)
synth = synthio.Synthesizer(sample_rate=22050)
audio.play(synth)
synth.envelope = synthio.Envelope(attack_time=0.1, release_time=0.6, sustain_level=1.0)
touchpins = [
board.GP2, board.GP3, board.GP4, board.GP5,
board.GP6, board.GP7, board.GP8, board.GP9,
board.GP10, board.GP11, board.GP12, board.GP13,
board.GP14, board.GP15, board.GP16, board.GP17,
board.GP18, board.GP19, board.GP20, board.GP21, board.GP22
]
THRESHOLD = 1000
touchpads = []
for pin in touchpins:
t = touchio.TouchIn(pin)
t.threshold = t.raw_value + THRESHOLD
touchpads.append(Button(t, value_when_pressed=True))
while True:
for i in range (len(touchpads)):
t = touchpads[i]
t.update()
if t.rose:
synth.press(60+i)
if t.fell:
synth.release(60+i)I did experiment with overclocking the Pico to give double the PWM frequency, using
microcontroller.cpu.frequency = 250_000_000
But although this did double the PWM frequency to around 244kHz, it didn’t seem to make much difference for the filtered signal.
Battery Power
One last thing I wanted to explore was if it was possible to power the touchboard with batteries. I left in a number of power options, so for this one I’m using the 5V/GND pin header. I’ve included a couple of capacitors for smoothing, and need to add the 1N5817 diode as shown below.
This requires the following additional components:
- 1x 1N5817 Schottky diode.
- 1x 100nF ceramic capacitor.
- 1x 47uF electrolytic capacitor.
- Jumper wires.
- 3 or 4 battery box.
The 5V/GND header pins connect to the Raspberry Pi Pico’s VSYS pin via the Schottky diode. The 1N5817 has a typical voltage drop of 0.45V, so combined with the Raspberry Pi’s accepted input voltage of 1.8V to 5.5V this means that ideally two or three AA batteries (at 1.5V each) would work. Four 1.2V rechargeables might be an option too.
It might be possible to get away with four 1.5V AAs, but that would give an input voltage of just over 5.5V, so I think that is probably pushing things too far. It might be a good use for some spent AAs though that are no longer reading a full 1.5V…
One of the downsides of battery power is that the touch works best when your fingers are at the same GND potential as the board. It works best if the GND pin of the (unpopulated) barrel jack is touched when using the board.
Closing Thoughts
With hindsight it would have been useful to have included a simple PWM output stage on the original board, but it is relatively straight forward to add one.
It might even be worth me making an add-on board that will connect to the header pins of the power and analog pins containing the simple passive filter components.
What is pretty impressive though, is how easy it is to use synthio with Circuitpython.
Kevin
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La setmana passada em va arribar aquesta joguineta d'Aliexpress i avui he estat com un boig programant en CircuitPython una cosa molt xula. Té a veure amb comandaments de trens, què deu ser? Dos USB donen mooolt de joc... 🚂
Espero tenir una primera versió ben aviat!
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Kodlama ile oynamak istiyorum ve mikrodenetleyici tarafında yeni ürünler var mı diye baktım ve içlerinden bir tek bu ilgimi çekti
#RaspberryPiPico için tasarlanmış, ama MicroPython ile çok basit, Atari seviyesinde oyun yapılmayacaksa #C /C++ yâni #Arduino istiyor!
Ne anladım ben bundan?
O zaman Arduino ile çalışacak şekilde tasarlasaydınız
Python ile bir Led Matrix ekranı bile sürülemiyorsa yuh artık!
Sanırım @adafruit 'in CircuitPython'u ile ancak basit Atari oyunları herhâlde yapılabilir!
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Last night was #robot arm class in Physical Computing & the #MakerSpace was electric with #CircuitPython #RaspberryPiPico #3dprinting arms battling to pick up candy! Learn such badassery at YouTube.com/@BuildWithProfG
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"Ghost Catch", an accessibility game I'm prototyping for the Campus School at Boston College, which allows children with severe motor restrictions to pass an animation back and forth. https://youtu.be/98N8J6Ri4L4 GitHub repo in description. #CircuitPython #MakerSpace #TechForGood #Accessibility #CSed
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Such a nice profile of the #AssistiveTech work being done by my Boston College Physical Computing students. https://www.bc.edu/content/bc-web/sites/bc-news/articles/2026/spring/the-class-that-makes-a-difference-.html May be interesting to folks in the #CSed #MakerSpace #RaspberryPi and #CircuitPython communities.
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90 min newbie intro to #CircuitPython #raspberrypipico workshop. Lights, sound, potentiometer, and servo! Slides I use with parts & code for all #csed & #makerspace educators can be found at https://bit.ly/pico-workshop If you want to see a student demo video see: https://bsky.app/profile/gallaugher.bsky.social/post/3mhnmurcaqk2f
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Diplo on your Pico! Build a polyphonic multi-sound DJ board on a sheet of paper using CircuitPython and a RaspberryPi Pico! https://bit.ly/pico-dj-board a super fun classroom build for the #CSed fam. @adafruit Adalogger Cowbell allows gigabytes of sound from the @raspberrypi Pico #circuitpython #raspberrypi #RaspberryPiPico #dj
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Fun lesson - Build a @raspberrypi.com pico DJ board while learning to use the @adafruit.com $8 Adalogger Cowbell to expand file storage to 32GB, & add a STEMMA-QT port with no wiring! My students built this in the MakerSpace last class & it was a blast! https://youtu.be/yZdR7oGbTX8?si=HQveNpNpnvKJrTJK #CircuitPython #CSEd
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#MakerSpace, #makered, STEMed and #csed folks, here's a super-fun challenge lesson I use in class: Build a Baby Groot who talks when his plant is touched. Uses #Adafruit #CircuitPython a Circuit Playground, a 3D printed planter, laser-cut box, but lots of options abound. https://youtu.be/gEmyZ7ZWMIo
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Some of my @bostoncollege.bsky.social Physical Computing students delivering their #CircuitPython based assistive tech projects to their clients in the BC Campus School. I’m so lucky to work with such wonderful young people. https://www.instagram.com/p/DTljI53jW9h/?img_index=9&igsh=MWFkZ21xdDB2c215Yg== #csed #assistivetech
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New #CircuitPython School lesson introduces key concepts: variable naming conventions, print & input for maker / electronics debugging, & AI code completion in PyCharm w/helpful & incorrect results. Also: Using AI for CircuitPython code explanations w/prompting examples. https://youtu.be/-wIqy7drCN8 #CSed
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Good luck #CSed faculty prepping for next semester. Show me your maker closets! Here's the cart with many (although not all) of the parts I use for PhysicalComputing: Art, Robotics, and Tech for Good - the #CircuitPython course I teach accessible from new-to-code through advanced CS students.
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Here's a link to today's CircuitPython exam: https://docs.google.com/presentation/d/1BeWUK_b5BKbo_GEi4BZVstnwV_1LJY5QNgVuA7ZbpdE/mobilepresent?slide=id.p
Students had to complete 8 builds in 2.5 hrs. Themes: "Magic-8 Ball Yoda", "Diwali Musical Chairs", An anti-cat distance-activated Turkey, & "Yip Yip Yip" martians from Sesame Street. Solution folder in the open course Google Drive at Gallaugher.com. #csed #maker #circuitpython -
Wonder what our CircuitPython exam is like? #CSed folks looking for new challenges for your own classes? See the Week 9 Keynote slides (.pdf also available) in the open Google Drive for the PhysicalComputing course at gallaugher.com. 7 fun challenges for a Raspberry Pi Pico and CircuitPlayground. Keynote slides have a video showing a proper build.
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The latest lesson for my PhysicalComputing course: Create an easy IoT dashboard for your Raspberry Pi Pico W / 2W with CircuitPython and free AdafruitIO. We'll toggle NeoPixel LEDs on/off, change light color, play sounds remotely, and move a servo using a slider. #csed
https://youtu.be/fjysAa3N2OI?si=mMn6cJOWNhgpA500 -
Use a Raspberry Pi Pico W (orig. or 2W) and setup a web page with a toggle to turn NeoPixel lights on and off. MQTT has never been easier to use. CircuitPython and free Adafruit.io makes it happen! An updated lesson I use in my PhysicalComputing course. Hack on! #csed
https://youtu.be/iFwvvEJ_UwA -
Use the buzzer to have your MCU play small wake-up melodies, signals, or music to accompany LED animations
https://www.makerspace-online.com/buzzer-music-simple-melodies-with-the-pi-pico/?utm_source=mms
#PiPico #buzzer #sound #MCU #OpenHardware #projects #code #programming #Arduino #CircuitPython -
Trouble remembering to take your meds? Build this reminder box with <$20 in parts to light up when it's prescription time. I leave mine by my coffee maker so I never forget it. Updated lesson for classroom build https://youtu.be/imafYENxZ_U #TechForGood #CircuitPython #MakerSpace #AssistiveTech #raspberrypipico
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ACEBOTT QD023 ESP32-based gesture control glove tracks finger movements with potentiometers
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Forbidden Planet “Krell” Display – MIDI CC Controller – Part 2
This revisits my Forbidden Planet “Krell” Display – MIDI CC Controller using my Forbidden Planet “Krell” Display PCB with a Waveshare RP2040 to create more of a “all in one” device.
Warning! I strongly recommend using old or second hand equipment for your experiments. I am not responsible for any damage to expensive instruments!
If you are new to Arduino, see the Getting Started pages.
Parts list
- Updated Forbidden Planet “Krell” Display (see below).
- Completed Forbidden Planet “Krell” Display PCB Build
- Waveshare Zero format device (I’m using an RP2040)
- 4x 6mm brass spacers
- 4x 20mm nylon spacers
PCB
This requires a built of the Forbidden Planet “Krell” Display PCB with the following:
- 2 potentiometers
- MIDI IN and OUT
I’ve used potentiometers that are their own knob, as they only poke through the casing by around 5mm or so.
If it you are able to get longer shaft pots, then that would probably be worthwhile.
Updated 3D Printed Case
This requires the following from the Krell Display 3D Printed Case:
- 1x Frame
- 2x Inserts (with potentiometer holes)
- 1x EuroRack support
This requires the following options in the OpenSCAD code:
show_frame = 1;
show_quadframe = 0;
show_insert = 1;
show_support = 0;
show_quadsupport = 0;
show_eurorack = 0;
show_eurorack_support = 1;
alg_pot1 = 1;
alg_pot2 = 1;
alg_cv = 0;The frame does not really take into account the PCB at present, but I’ve reached the “good enough I want to do something else” stage, so I’ve just added a couple of small cut-outs (using a hacksaw) for the two MIDI sockets, and am content that the components stick out a bit from the back.
This cutout has to be 10.5mm from the end, 6mm wide, and 5mm deep.
At some point I might go back and design a deeper frame that has the cut-outs included and some kind of snap-on back to make it a self-contained box.
But for now, this is left as an exercise for, well, anyone else 🙂
Construction
I’ve used four brass 6mm spacers to screw into the mounting holes in the frame. Then the PCB can be inserted, taking care to squeeze in the 3D printed support around the LEDs and pots, and fixed with 20mm spacers which will also act as “legs”.
The Code
I’ve used a Waveshare Zero RP2040 and Circuitpython for this build. This is a combination of some of the test code used for the Forbidden Planet “Krell” Display PCB but with added MIDI.
The code supports both Serial and USB MIDI.
I wanted an equivalent of the Arduino map() and constrain() functions and didn’t immediate spot them in Circuitpython so wrote my own:
def algmap(val, minin, maxin, minout, maxout):
if (val < minin):
val = minin
if (val > maxin):
val = maxin
return minout + (((val - minin) * (maxout - minout)) / (maxin - minin))This allows me to map the analog read values (0 to 65535) down to MIDI CC values (0 to 127) whilst also allowing for some inaccuracies (I’ve treated anything below 256 as zero for example):
alg1cc = int(algmap(alg1_in.value,256,65530,0,127))
I’ve used the Adafruit MIDI library, which I’m still not really a fan of, but I wanted to include MIDI THRU functionality to allow the controller to sit inline with an existing MIDI stream. But it doesn’t seem to work very well.
I was already only updating the LEDs/MIDI CC if the pot values had changed, to cut down on the number of Neopixel writes required.
I experimented with changing the scheduling of the analog reads and MIDI but that didn’t seem to help very much. In the end I made sure that all MIDI messages queued up in the system would be read at the same time before going back to checking the pots.
msg = midiuart.receive()
while (msg is not None):
if (not isinstance(msg, MIDIUnknownEvent)):
midiuart.send(msg)
msg = midiuart.receive()It will do for now. Moving forward, I might try the Winterbloom SmolMIDI library. If that still doesn’t give me some useful performance then I might have to switch over to Arduino C.
Closing Thoughts
The MIDI throughput is disappointing, but then I’ve never really gotten on with the Adafruit MIDI library. I use it as USB MIDI on Circuitpython is so easy, so will need to do something about that.
I’m still deciding on the PCB-sized supports too. The original seemed to have nicer diffusion of the LEDs, but that could have been the difference between 5mm SMT neopixels and these THT APA106s which seem more directional in the first place.
And I really ought to finish the 3D printed case properly too.
So this is “that will do” for now, but I ought to come back and finish it off properly at some point.
Kevin
#APA106 #circuitpython #ForbiddenPlanet #Krell #midi #midiController #NeoPixel #potentiometer #rp2040 #WaveshareZero
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#CircuitPython2026 please get Bluetooth working on the Pico W so we can use these awesome little boards to building awesome BLE devices (including keyboards with #kmk
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Wrapped up my latest custom #keyboard today. It’s a single handed keeb designed exclusively for playing #ArcRaiders . Designed in TinkerCad and #3dprinted on my #Prusa mk4. Then hand painted with Panduro Hobby Acrylics and dusted with weathering powders. Running #kmk on a #seeed Xiao #rp2040. #circuipython #kmk
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Finally calling this done! Say hello to the HellSplit a hand-wired, asymmetric 40% split #ortholinear keyboard with vertical column stagger and two rotary encoders. Powered by a pair of Raspberry Pi Pico's #RP2040 and #KMK firmware
#mechanicalkeyboards #splitkeyboard #ergo #otho #mechkb #splitkb #pipico #raspberypipico #40percent #handwired #circuitpython @circuitpython @RaspberryPi @rpimag
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@tobozo I tried it. What a difference!
Now the RSSI is at around -40 to -42 and there are no send errors, send retries or send timeouts since I added the antenna.
Very cool 😎 as I can keep using these modules after all.
I also figured out how to get them fully running on CircuitPython.
This was my first time soldering after probably more than 20 years ...
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Have to expand the list based on the replies.
Probably more out there.5) MicroPython (Python; REPL)
6) PlatformIO (C; VS Code)
7) CircuitPython (Python; REPL; Onboard IDE) -
🎄Reminder that @pyladiesdub end of the year event is on tomorrow evening& kindly hosted by DIGIT Games Studio. 🍕☕️
🍪💻 I'll be bringing freshly baked cookies & some wip #CircuitPython projects.
🧣Keep warm and see y'all there tomorrow evening!
#mastodaoine #pyladies #IrishTechCommunity #diversityintech #python #PleaseShare https://mastodon.ie/@whykay/113475608499071813
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How to Re-initialize a Stuck #ESP32 (in #CircuitPython) -- something I needed when working on my particulate air quality #sensor but I'm sure I'll need it for many other projects:
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#introductions my name is Andy and I’m a British expat living in Amsterdam, NL (for ten years now!). I’m a designer (manager) by trade and a maker in my heart.
Follow me for:
#maker
#3dprinting
#electronics
#raspberrypi
#MechanicalKeyboard
#HandWiredKeyboard
#SplitKB
#RaspberryPiPico
#circuitpython
#neopixels
#rgbleds
#companionbot
#internetofthings
#HomeAssistant
#EspHome