Simple zynthian board



AdditionnAl parts are needed:

  • wm8731 board14.00€ shipping incl
  • or pcm5102a board, 3.50€ shipping incl
  • 3.5 inch SPI display, 12.50€ shipping incl
  • Step down converter, 1,50€ shipping incl
  • 4 rotary encoders, 4 dip switches 6mm, 2x20 pins female header (tall enough so that board can fit above USB ports), 1x11 pins female header for the wm8731 solution or, 1x6 + 1x4 pins male header for the pcm5102a solution => less than 10€
  • I’ve just ordered 5 boards to jlcpcb for 30€ (using a coupon and with the cheapest shipping method) => 5€ per board
    So the total cost without the RBPI is around 50€ (with the wm8731 board).

For the price, you’ve got:

  • stereo in or mic in, stereo out
  • the RBPI powered through the GPIO with a protection circuit
  • ability to adjust the power voltage
  • ability to power the synth with a battery pack
  • a compact sized synth: without box 10x10x4 cm

Well that’s in theory :sweat_smile: :sweat_smile:
It’s my first design sent to production, so fingers are already crossed :zynface:

Additionnal notes:

  • I didn’t tested the wm8731 board yet because crystal and the two capacitors for the oscillator circuit are missing.
  • The display doesn’t work out of the box with its ili9488 driver chip. I had to use some frame buffer copy trick.
  • touch function hasn’t been tested yet (lack of time)
  • when using the pcm5102a board, the digital signals and also the power have to be wired with real wires
5 Likes

@le51 looks great keep us updated!

This cheap Chinese board variation was probably intended for a system with an external clock source, which is a big pain. Is there a connection to pin 25 ( XTI/MCLK) ?.

(The AudioInjector boards using that chip have a 12Mhz crystal hidden on the bottom, one example application shows 22pf capacitors. There’s a fair chance the Audio Injector driver option could work with your board with added crystal.

From page 31 pf the chip specs:
"For applications where a component other than the WM8731/L will generate the reference clock, the external system can be applied directly through the XTI/MCLK input pin with no software configuration necessary. "

The AudioInjector board with Raspberry Pi header is about the same price as the Aliexpress part, if you arrange free shipping on Amazon.

— A couple of headless demo connection guides, which could provide one starting test setup

Quick guide running naked headless Zynthian, setting up CC buttons to cycle through presets.

No, there are footprints on the board for soldering the oscillator and the two capacitors.

Another aliexpress seller photo with the crystal is omitted, you can see one of the Y1 pins has an external connect trace for applications that are using an external clock, at least this one gives a visible warning of the absence of a crystal in the PCB photo.

I hope the 12Mhz crystaand 22pf capacitors info helps you finish your board…