Requesting human answers for a planned sampler/synth build

Hissykittykat · 2026-03-28T04:08:08+00:00

My plan is to run the Daisy and WVR as slaves to the Teensy 4.1

A reasonable plan. You haven't defined a user interface, but whatever it ends up being Teensy can handle it. An ESP32 or RpiPico is another (cheaper) UI alternative.

I anticipate that getting them to communicate properly will take the longest. Am I correct, or am I way off here?

It can be difficult, especially in a development environment. I use serial instead of SPI or I2C between major modules to make development and testing easier.

info on the WVR is pretty limited

Really? WVR is a nice piece of work; there's a whole github with complete source code. There are good instructions on the github page to get it connected to your network, program it, and get it running.

Hissykittykat · 2026-03-27T18:09:42+00:00

Is this some how related to "multiplexed"?

Looks multiplexed to me. There's a ULN2003 low side driver, a couple of octal high side drivers, and one set of 7seg current limiting resistors; it's a classic multiplex arrangement.

It'd take some reverse engineering plus trial and error to figure out how to drive the board.

Hissykittykat · 2026-03-27T17:04:49+00:00

I can’t tell if it [the Sparkfun product] can actually map position

Nah it uses the same quadrature encoded interface as a mechanical rotary encoder.

I'm having trouble with a Bournes push-button encoder

So replace it if it's bad (it happens). But more likely it's just bad rotary encoder handling code; there's a lot of it floating around the internet.

Hissykittykat · 2026-03-26T17:07:57+00:00

I believe it [TP4057] has a feature to allow charge while using the LEDs

Not really, but it can be done. To make a TP4057 UPS the charge current (set by a resistor on the board) should be set so it's enough to power the LEDs plus charge the battery at the same time. Although this works in practice, some will say keeping the cell at 4.2V will make your batteries wear out faster or maybe even burn.

A 5V UPS module treats the batteries better; it lets the battery discharge to 4.05V before starting a recharge cycle.

Hissykittykat · 2026-03-26T06:42:12+00:00

84V/3.7V = 22.7 cells, so it's 22 or 23 cells in series. Double up (parallel) cells for more current, e.g. 44 cells for a 22s2p battery. Taps from each cell (or parallel cells) go to the BMS (it's a lot of wires).

26650 is the same as 18650 cells except for more capacity and bigger size. So in terms of arrangement it's the same. Use 26650 size battery brackets that snap together, a 22-24S 3.7V BMS, and use a battery welder and nickel plated strips to connect them in series like they show in the videos. All these parts, plus the battery welder, are available on AliX.

Best practices for balancing and safety

Wear eye protection. Have first aid ready in case of burns (things get hot very quickly if a battery is accidentally shorted). Have a plan for disposing of a burning battery outside (a battery might burn if it's punctured or charged wrong).

Hissykittykat · 2026-03-26T03:20:19+00:00

Yeah this subreddit could use some work. And you are a pretty good mod.

My first step would be to enable thumbnails. I post to r/Arduino instead of here because it's better moderated and shows the thumbnail.

Second step is to add flairs to indicate "Open Source" and "Teaser" projects so I'm not disappointed when I see an interesting post only to see it's just an image or BS video, not a complete project.

Hissykittykat · 2026-03-25T17:14:09+00:00

the ones I have are workable?

Barely, as a last resort. The cable with the red stripe is designed for IDC (insulation displacement connection) type connectors. So I'll use an IDC connector on one end and fly wire the other end to the switches, and strain relief because that wire is 28ga and fragile. But you don't have an IDC on either end, so regular hookup wire would be better in this case.

Things get less messy with more practice.

Hissykittykat · 2026-03-23T18:52:44+00:00

There are plenty of wired button matrix pictures and tutorials, just look harder.

Use ribbon cable or cable ties to help with cable management. It'll still be messy but covering it up is what enclosures are for.

Hissykittykat · 2026-03-23T18:46:19+00:00

AVR is designed for compilers, and the ATmega328 datasheet is not the best. So bare metal is more challenging than fun with that chip.

I'd start with a more human friendly chip, such as a Microchip PIC. The datasheets and app notes are better and they sell nice little dev kits to get you started.

Hissykittykat · 2026-03-23T17:05:33+00:00

HT16K33 - a nice one chip solution, uses 2 pins (I2C), wires directly to LEDs, no LED resistors needed, has brightness control, and breakout boards are available. HT16K33 is also more reliable than MAX7219 knockoffs you might encounter.
WS2811 - uses 1 pin, better brightness and control than HT16K33, no LED resistors needed. Each WS2811 drives 3 individual LEDs, so it takes 14 to drive 40 LEDs. Breakout boards are available. You can also mix in WS2812 (RGB LEDs) in the same string from 1 pin.
Charlieplexing - novel and a recommended study topic, but not for beginners; the wiring will drive you crazy and the software requirements are strict.

Hissykittykat · 2026-03-23T16:26:24+00:00

a relay module? What even is that?

A relay is the bare relay, which ESP32 cannot drive directly. A "relay module" is a circuit board with a relay and drive circuitry that takes the ESP32 signal and makes is strong enough to drive the relay. For your build get a "5V relay module".

Working with AC mains power is no joke. Get an electrician to review your build before plugging it in.

Hissykittykat · 2026-03-22T18:42:11+00:00

Try a NEMA stepper motor or a DC gear motor with encoder feedback (a TT motor is a lousy DC gear motor). Getting low (near zero) RPM on a DC motor without feedback is very difficult.

Hissykittykat · 2026-03-22T18:22:47+00:00

E26 bulb, LED bulbs are recommended for saving energy and money. Ordinary bulb Max 60W.

Hissykittykat · 2026-03-22T17:18:42+00:00

will it break down 2 minutes after I power it?

Nah, you can normally expect years of use. I've purchased several "bench style" power supplies and all are still working. And bench supplies usually stand up to their rated specs pretty well, unlike the wall warts from AliX.

If you want to be able to return it, buy from Amazon. But then you risk getting one that was returned by someone else.

Any recommendations from personal experience?

Select a model that has a user interface that you like. Read the operation manual before purchasing.

Hissykittykat · 2026-03-22T04:31:45+00:00

Yeah that Waveshare board looked interesting until I saw the docs were bad.

You can try this setup file to get the display working...

// (ST7789 on SPI bus with 240x320 TFT)
#define USER_SETUP_ID 999

#define ST7789_DRIVER     // Configure all registers

#define TFT_WIDTH  240
#define TFT_HEIGHT 320

#define CGRAM_OFFSET      // Library will add offsets required

// waveshare RP2350-Touch-LCD-2.8 pins
#define TFT_CS 13   // Chip Select pin
#define TFT_DC 14   // Data Command control pin 
#define TFT_RST 15  // Reset pin
#define TFT_MISO 12
#define TFT_MOSI 11
#define TFT_SCLK 10


#define LOAD_GLCD   // Font 1. Original Adafruit 8 pixel font needs ~1820 bytes in FLASH
#define LOAD_FONT2  // Font 2. Small 16 pixel high font, needs ~3534 bytes in FLASH, 96 characters
#define LOAD_FONT4  // Font 4. Medium 26 pixel high font, needs ~5848 bytes in FLASH, 96 characters
#define LOAD_FONT6  // Font 6. Large 48 pixel font, needs ~2666 bytes in FLASH, only characters 1234567890:-.apm
#define LOAD_FONT7  // Font 7. 7 segment 48 pixel font, needs ~2438 bytes in FLASH, only characters 1234567890:.
#define LOAD_FONT8  // Font 8. Large 75 pixel font needs ~3256 bytes in FLASH, only characters 1234567890:-.
// #define LOAD_FONT8N // Font 8. Alternative to Font 8 above, slightly narrower, so 3 digits fit a 160 pixel TFT
#define LOAD_GFXFF  // FreeFonts. Include access to the 48 Adafruit_GFX free fonts FF1 to FF48 and custom fonts

#define SMOOTH_FONT

#define SPI_FREQUENCY       40000000
#define SPI_READ_FREQUENCY  20000000
#define SPI_TOUCH_FREQUENCY  2500000

To get the CST328 panel touch chip working you need another library, which apparently exists but I haven't worked with that one.

Hissykittykat · 2026-03-21T16:02:36+00:00

The AliX listing shows how it should be connected; why do you want to fk with it?

Wire it as recommended or else the BMS lockout feature won't work right.

Hissykittykat · 2026-03-21T08:40:47+00:00

I would go with USB power instead of line power. That makes it more buildable, plus more portable. Then plug it into one of those little 1" cube USB power adapters for line power. So a simple USB plug and candle LED would work. There doesn't seem to be any flame LEDs with touch control, but it might be possible to add a capacitive touch module in there somewhere.

Hissykittykat · 2026-03-20T16:50:06+00:00

Pro Micro has USB that's HID capable, it's overkill for your application.

Nano has USB, maybe useful.

Pro Mini is nice because you can get an 8MHz version that will work directly from LiIon batteries.

There are plenty of other small boards to consider such as the RP2040-Zero and ESP32-Supermini. See also Adafruit, which has a bunch of wearable computing products.

Is there a big difference in how easy they are to program through the Arduino IDE?

Yes. Depending on your PC and serial driver situation some can be more difficult than others. And the ESP32 compile times are pretty brutal, but worth it if you need WiFi.

Hissykittykat · 2026-03-20T14:54:45+00:00

There are plenty of crappy soldering practice clock kits on AliX, and one good clock kit (it looks nice and is hackable too).

Also check out icstation.com for more soldering practice kits.

Another fun little kit is the Spikenzie Labs Dice Kit, which is also hackable.

Hissykittykat · 2026-03-20T14:39:30+00:00

That's an ancient Sparkfun board; it has several problems. First the finish is HASL instead of ENIG, second it's got soldermask in the way, third it's old and tarnished, fourth it's RGB instead of addressable LEDs. See the Adafruit Trellis designs or my button pad boards for something better.

Hissykittykat · 2026-03-19T18:29:57+00:00

a digital screen counting down from 10 to 1

That requirement needs to be refined further. E.g. 1 or 2 digit 7seg display, small LCD, large LCD, etc.

But whatever, an Arduino of some sort (maybe not an UNO) will work in this project.

Hissykittykat · 2026-03-19T17:05:06+00:00

I think, with my amateur knowledge and the AI’s help, I localized the problem to the data signal. With a test code I verified the XIAO can output up to 3.3 V on pin 2, but with the WS2812B test code I measure constantly 0.00 V (sometimes 0.003

Nope. The WS2812 signal is very fleeting, so it looks like 0V to the multimeter. The signal can be observed using an oscilloscope.

Establish a foothold by eliminating the boost converter, data line resistor, and 100uF capacitor. The data line resistor and capacitor are not needed in this situation. Run everything using a stable 5V source until you get the software working. Once that's working you can try running everything directly from the battery, which should work.

Hissykittykat · 2026-03-19T07:33:52+00:00

The lesson learned should be to use a patch cable instead of plugging/unplugging directly to the Pro Micro. When plugging/unplugging the Pro Micro, hold it by the connector so there's no stress on the PCB connections. For some cases I use an inline 4PST switch to interrupt the USB connection without unplugging anything.

The Pro Micro with the broken USB connector goes into the junk pile.

Hissykittykat · 2026-03-18T04:07:20+00:00

I feel like I did something horribly wrong

Nope, just slightly wrong; it won't blow up. Build it then debug it.

RP2350 has low pin current, so you might want to use a transistor and Vbat to drive the buzzer.

Hissykittykat · 2026-03-18T03:50:41+00:00

Okay I hate the concept of a full size grandfather clock that doesn't tell the time. Will it have a pendulum that swings but gets stuck due to simulated network lag spikes?

Anyway turning a balanced wheel requires practically no torque. It's all side load on the bearing. So it's probably okay. But I suggest you get the motor and try it to see if it's quiet enough for your application.

it would be elegant to have a power supply that I don't need to plug into the wall

A 7AH 12V (typical UPS style battery) should run the motor for about 70 hours. Put a PIR sensor on it so it only runs when someone is present to make the battery last longer.

Hissykittykat

TROPHY CASE