3,5“ Display and MIDI

Hardware
#1

Hi,
i just started a custom Zynthian build, after I had a RasPi4 some months and had nothing else to do with it.
I will use 4 Arcade-Buttons for UI-Control and a 3.5“ Touchscreen.
The Buttons are connected to GPIO and work so far. Today I got the display working. I had some problems with inverted x-axis but it all works now.
Now I would like to know what GPIO-Pins the Display actually uses (Cheap Screen, works with the RasPi 3.5, V.1-Settings), because I want to build MIDI In/Out-Circuitry which I want to connect to the GPIO-Pins.

Can anybody help me on how to do that? I would like to use some form of extension to connect the Display only to the Pins it needs, so I can use the other Pins for MIDI In/Out (and possibly for Aufio too).

Best regards,
J.D.

#2

Hi @batidadeloco! Welcome to Zynthland. The natives are pretty friendly.

The pins used for the screen will depend on what screen you are using. It sounds like you have a screen similar to the official Zynthian screen so you can look at the schematics on the wiki and in GitHub.

MIDI is already implemented using the standard Raspberry Pi UART serial pins 8 & 10.

#3

The ones called “UART”

#4

also, Zynthian is “open sourced” hardware , have a look here

And, welcome …

#5

Hi,
thanks for the replies and the worm welcome.

Ok, to I can connect the MIDI Circuits to Pins 8 and 10, but that still leaves the question, if all other Pins that are blocked by the Display are needed for the display, or does the display only use like 10 Pins.
I‘ll look in the Wiki, but so far I din‘t really find the information I‘m looking for, but still, I can get in done now, maybe I‘ll just connect more Pins to the Display than needed :wink:

I‘ll report my progress here.

#6

If you post a link the display you have used we may be able to help. Each display may use different pins so not knowing which you are using makes it a bit awkward to advise.

#7

image

This is the 26 pins header of the official Zynscreen.
PIn numbers used by the screen are: 15, 18, 19, 21, 22, 23, 24, 26

Most of cheap chinese 3.5 inch displays are a Waveshare clones. If yours looks like this:

then have a look here:

#8

Thanks, you all are a great help!
It is, in fact, exactly looking like that, so it‘s most likely a waveshare-clone.
I have a cable wich I will use to extend the connection to the display and break out the MIDI-Connections. As an audiointerface I will use a USB-Interface, so it should work then…