This is a purely hardware prototype.

Getting the VS1053 to play an MP3 file (from flash is fine) on any kind of microcontroller is probably a good first step.

Next is doing the same but on an ESP32.

Finally, on an ESP32 with an SD Card.

• 🎶
• VS1053 + esp-idf
• + an SD Card

Unfortunately, this involves figuring out how everything is laid out and possibly CAD.

It's currently 3.3V (which is the rated maximum acceptable voltage) while the nominal voltage is 2.8V.

We can fix this by putting a diode with roughly a 0.4V or 0.5V drop in series with the display's VDD. The diodes we're using for the buttons might be appropriate.

We need to ensure that:

• the chosen diode can handle the display's current draw
• the voltage drop yields a voltage that's comfortably within the display's acceptable range

As .tsv files!

We've got one leftover IO pin, might as well use it!

This should only affect the SD Card.

There are so many!

This is another issue we carried over with us from the V0 schematic; a pull up with the same resistor, but to VCC instead of GND should do the trick.

One end of the button should be tied to the same net as the resistor/capacitor feeding into the NAND gate. The other end is connected correctly.

The concern here is pin mapping; the ESP32 has a lot of restrictions about what pins can and can't be used depending on the specific variant used and other hardware factors.

Running the example SD Card program with the pin map in Board V0 successfully is all we're looking for here. The only thing to watch for is that we ensure that we're using the 4 line SD Card interface and not just SPI.

I2C pins (SDA, SCL), CHANGE, and power and ground. 5 pins in total, pull-ups on SDA, SCL, and CHANGE.

Before we manufacture board V0, we should build and test the ADC/digital in button circuit.

Since we're mostly concerned about the electrical soundness of the design, we can test this on a breadboard with a TM4C.

We should check that:

• each button yields a different ADC reading (the ESP32 and the TM4C both have 12-bit ADCs but really we shouldn't need nearly that much resolution for this)
• all combinations of the five buttons yield discernible readings (not required but this should be possible if the design works)
• single or multiple buttons being pressed result in the digital input going high
• the digital input is adequately de-bounced
• the circuit never draws excessive amounts of current (<1mA)

This is a lot for a single issue.

It's hard to make a comprehensive list so far out, but here's a quick brain dump of the things I can think of now. This is split into the top and bottom parts.

Bottom:

• spots for the magnets (need to wait for #14)
• lip for the PCB
• side hole (left?) for the LED
• groove for the battery
• notches for the headphone jack, USB connector, and microSD card slot

Top:

• matching magnets spots
• aligned cutout for the display + lips for the plastic housing
• aligned cutout for the clickwheel PCB + nubs for the holes
• slightly smaller inner diameter on the acrylic wheel for support for the inner button
• inner button piece; aligned to the acrylic wheel's inner diameter + with a lip aligned to the PCB's inner diameter

Misc:

• export the board files as CAD
• touch up the Eagle parts we're using; add CAD where possible
• rounded corners, a chamfer
• pattern on the bottom?
• labels, logos, writing on the bottom?
• a texture, bumpy style?

This is again mostly about the hardware; particularly the actual wheel geometry.

Things to check for:

• verify that MODE and RESET work as expected; neither is connected to the ESP32 in Board V0
• that we can get read readings from the wheel!
• how thick we can make the thing sitting on top of the wheel
• guard channel?
• that CHANGE works as expected

they have to be small and strong and narrow and thin

and also cheap

Our resistors are bigger.

The VS1053 also has 2 extra pins.

The charge IC may have some mechanism for this; needs exploring.

Need to do a sweep for this.

The resistors should be away from the buttons, the buttons aren't aligned, and the display is extremely close to the VS1053.

Just like #15 but for our caps.

One resistor and one capacitor, per button.

We settled on 0402 caps for layout reasons, but some of the higher capacitance parts we're using (>2.2 μF) aren't actually available in this size.

Since revision A has already been ordered, we'll have to push off physical changes to the board until revision B (i.e. switching to larger package sizes where we need to). To salvage revision A, we'll use smaller capacitance capacitors where we must and physically larger capacitors where we are able to.

These appear to be the affected capacitors:

• C1
• C3
• C4
• C5
• C22
• C24
• C26
• C27
• C28
• C29
• C32
• C37
• C43

Actually using CHREN/CHR0/CHR1 in the right way is probably not going to happen, but we can at least disable charging when we know we're not plugged in.

Alternatively maybe we disable charging unless we're on a 500mA/1.5A supply (CHR0/CHR1).