What's that ALTERA chip for on ZynScreen?

Hi Fernando,

I’m exploring some options for Zynthian-Hat and found out that there is ALTERA FPGA on Zynscreen. I as curious person would like to ask, what for? Display itself is using SPI. Or do you translate SPI stream into parallel access into LCD controller via this FPGA?


And next question, have you ever considered to use display as complete Zynthian shield for all essentialities, as MCP, MIDI, I2S populating, maybe alternative power delivery option?

@Mark_OzzMaker, please, could you satisfy @sailort’s curiosity? :wink:

No. Current IC distribution seems OK to me because it eases case-mounting, avoiding too much wiring going from case-top to case-bottom. Currently only the 26-pins ribbon segment connects both parts, and it’s very comfortable to manage. Also, it seems elegant to me having all the “UI-circuitry” in the case-top, while having the processing and audio/MIDI circuitry in the case-bottom.


This statement is correct ;

The Altera CPLD acts as shift register and converts the single SPI output from the Pi into a 16 pin input needed by the LCD


So it needs some kind of firmware/code? Is this free or some proprietary closed source?

this is my first attempt (but still work in progress) to achieve this kind of thing:


  • display: cheap one from ali express with ili9431 driver (supported)
  • codec: wm8731: stick to the wolfson reference design
    PCB size is 100x86 mm and with components on the same face to conform to jlbpcb.com conditions for:
  • 5 pcb for 2$
  • free assembling (*)

As said, still a work in progress and it will, quiet for sure, never been achieve. It’s the way I use to learn how to use kicad, freecad and understand how these electronic stuff works.

(*) when using standard components, otherwise it’s +3$ per each non standard component (like wm8731, mcp23017 and so on)


That’s a good start. Please consider optional power input and if possible, audio ins/out on some header in case of eurorack mounting. That’s what I like it to have it :wink: Maybe I’ll start to design my own to better help, as there is a lot of dimension constraints as I come so far in mind visualization.

  • height of display vs height of encoders
  • display header too long, probably connected with very short cable
  • need of some display fixing, cheap AE displays doesn’t have mount holes, so some stacked frame
  • size of 100mm is too litlle (I know, there are that tempting prices at PCB houses under this magic number) - yours sketch seem to have issue with screen access when mounted so close
  • even come to idea of custom display implementation (one without board), as it could simplify things a lot, so there comes my ALTERA question from :wink: