To create your own smooth multitrack recorder hardware for mixer consoles like Mackie DL16S/32S/DL32R and Behringer X32/XR18 based on Raspberry Pi 4, the following information is needed:
Bill of material:
- Raspberry PI 4, 2MB or more (Raspberry PI 3 will probably work fine also)
- RP4/RP3 Case with 3.5″ touch display
- 16GB SD Card with Raspbian OS (Latest version)
- USB 3.1 memory stick / transfer rates above 130 mb/s or a SSD disk
- Z-LiveRec application for RP4
I picked up a cheap 3.5″ screen kit on Ebay with case and heatsink for about $15.
To assembly the PI 4, screen in the case with heat sink is pretty straight forward. But how to enable the 3.5″ XP2046 type display via SPI in Raspbian with touch support also enabled? Not completely obvious – there is a lot of confusing information and links pointing to strange driver installations etc…and they all had in common are they never worked – however I found a post written by somebody that had made the journey for real.
The secret remains in the fact that the drivers are already built into the kernel using the latest version of Raspbian PI OS version 2021-05-07. Note: So you don’t need to install any other manufacturer drivers. The only driver needed is for the touch screen part.
Preparations: Download and install the Raspberry PI Imager app from Raspberrypi.org to your PC or MAC.
- In the Imager app, select the Raspberry PI OS (32Bit)
- Insert an empty 16GB MicroSD card in your PC.
- Choose storage – select the 16 GB MicroSD card
- Click “Write” to generate the OS MicroSD.
- When ready – install the card into your Raspberry PI and boot it up against a HDMI monitor.
- Follow the generic installation and setup scenario.
First of all enable SPI by using the terminal and the command:
Navigate to ‘Interfaces’ and then enable SPI function.
Reboot if needed through the command in the terminal:
The touch screen should turn on and be white colored.
Give the following command to update and upgrade Raspbian to the latest:
sudo apt-get update
sudo apt-get upgrade
To get all the lastest!
Now to modify the configuration file to configure the display:
sudo nano /boot/config.txt
then add this line to the bottom, In the PI4 section, add the following:
(You can comment out the existing #dtoverlay=)
Press Ctrl+X, Y, and Enter. (To save the file)
Give the command:
Important: Unplug your HDMI cable now!
You now see Raspbian booting up on the 3.5 inch screen.
At this point your mouse and touch screen will probably be moving backwards. In the newer versions of Raspbian (Raspberian Buster) they changed input control from evdev to libinput. You need therefore to install evdev or it will ignore your screen settings found in the conf file 99-calibration.conf configurations.
sudo apt-get install xserver-xorg-input-evdev
You can now modify your 99-calibration.conf file
sudo nano /usr/share/X11/xorg.conf.d/99-calibration.conf
Copy and past below
MatchProduct “ADS7846 Touchscreen”
# Don’t use libinput but evdev for the touch screen and the pen
Option “Calibration” “3936 227 268 3880”
Option “InvertY” “false”
Option “InvertX” “false”
Save the file by using the CTRL-X – Y + Enter command.
Your Raspberry Pi 4 should come up now on the 3.5” Touchscreen and it should be working in the right direction.
Note: If you need to run the raspberry pi on the external hdmi monitor again…just plug-in the hdmi cable again – pretty smooth!
You can now install Z-LiveRec app according to the manual.