What's the size/resolution of the HDMI displays which you've ordered?
In all Peppy Player disk images which I distribute I use console mode for UI which is based on Raspbian Lite OS. It means that the player's UI is the only UI and there is no desktop UI. At the moment I don't know how to output two different UIs (for left and right channels) to two HDMI displays connected to Pi 4 using lite OS. This needs investigation.
Having two PeppyMeter UIs running on the same Pi can consume too much CPU. Therefore the idea with separate Pi Zero per channel looks very attractive as the main Pi will be off-loaded. Pi Zero is very cheap - $5 (version w/o Wi-Fi):
https://www.adafruit.com/product/2885?g ... gK81vD_BwE
and it has HDMI output. The only question - can Pi work as I2C receiver? That also needs investigation. If it can then the hardware looks pretty straightforward:
- Pi Zero listens for I2C signal and running PeppyMeter modified for I2C input (right now it has only named pipe input)
- HDMI display connected to Pi Zero
This can be pretty generic kit. So you could feed it with I2C data either from "main" Pi 4 or from ADC which can output I2C. You can connect such "channels" as many as you want. I2C supports many devices over the same line.
The overall system setup could look like this:
- Main Pi 4
- DAC or Digi or Amp on top of the main Pi
- Two "channel" kits connected to the main Pi through I2C. One kit includes one Pi Zero and one HDMI display.
LCD provides additional benefits - you can display Spectrum Analyzer in addition to VU Meter. I even thought about Peppy Player version with two or three LCDs
One could be used for main player UI and two others for VU Meter/Spectrum Analyzer.
I'm not sure I understand the issue which you described - using ADC and DAC together.
So two open questions are:
- How to output two different pictures to two HDMI displays connected to Pi 4 using Pygame library and Raspbian Lite OS. This actually is not required if the idea with I2C channels is in use.
- Can Pi work as I2C receiver? Posted question here: https://www.raspberrypi.org/forums/view ... 8#p1596548
P.S. Cheaper versions of the same ADC can be found on Amazon and eBay: