Template: 13.3inch PiPad C4 Guide

Write Raspberry Pi OS

Download the lasted Raspberry Pi OS image from the Rasberry Pi website and write it to an empty micro SD card.
- Write Image for Compute Module Boards eMMC version
- Write Image for Compute Module Boards Lite version
Create a new Txt file under the BOOT directory of the micro SD card and name it SSH.
Modify the config.txt file which is located in the BOOT directory, and add the following lines to the config.txt file.

hdmi_group=2
hdmi_mode=82
hdmi_cvt 1920 1080 60 6 0 0 0

Save and insert the micro SD card into Raspberry Pi.
Connect the Magic mirror to the network and power on Raspberry Pi.
After booting, you can access Raspberry Pi via SSH/VNC, or directly connect the keyboard and mouse.

Check the USB Audio Card

Test the sound output device:

aplay -l

Test the sound input device:

arecord -l

USB2.0

To reduce consumption, USB interfaces are disabled in CM4 by default. If you need to use USB ports, please add the following line to the config.txt file.

dtoverlay=dwc2,dr_mode=host

Then reboot the CM4. If you use the newest Bullseye image, the USB2.0 is set to OTG mode by default and occurs the error in CM4:

config failed, hub doesn't have any ports! (err -19)

To remove the errors, you can remove the line otg_mode=1 from the config.txt file and add the line:

dtoverlay=dwc2,dr_mode=host

Kepp Display Always On

Modify lightdm.conf.

sudo nano /etc/lightdm/lightdm.conf

Find the line "Xserver-command" below the [SeatDefaults] section and change it from:

#xserver-command=X

to

xserver-command=X -s 0 -dpms

-s # – set screen saver not enabled.
dpms turn off power saving management.
Then save and reboot:

sudo reboot

RS232

To use the RS232 interface, please modify the config.txt file:

sudo nano /boot/config.txt

Add the following line to the file and save.

dtoverlay=uart3

RS485

To use the RS485, you need to enable the serial port of the PI.

sudo raspi-config

Choose Interface Option -> Serial -> No -> Yes, then reboot.

Keys Description

1: Open or Close LCD display. If you don't need the LCD for a long time, you can use this button to reduce consumption.
2: Direction button.
3: "OK" function.
4: Open the menu and the "Return" function.

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