Raspberry Pi
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Intro
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=====
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These instructions apply to all models of the Raspberry Pi:
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- the original models A and B,
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- the "enhanced" models A+ and B+,
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- the model B2 (aka Raspberry Pi 2)
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- the model B3 (aka Raspberry Pi 3).
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- the model B4 (aka Raspberry Pi 4).
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- the model CM4 (aka Raspberry Pi Compute Module 4 and IO Board).
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How to build it
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===============
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Configure Buildroot
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-------------------
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There are two RaspberryPi defconfig files in Buildroot, one for each
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major variant, which you should base your work on:
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For models A, B, A+ or B+:
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$ make raspberrypi_defconfig
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For model Zero (model A+ in smaller form factor):
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$ make raspberrypi0_defconfig
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For model 2 B:
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$ make raspberrypi2_defconfig
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For model 3 B and B+:
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$ make raspberrypi3_defconfig
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or for model 3 B and B+ (64 bit):
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$ make raspberrypi3_64_defconfig
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For model 4 B:
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$ make raspberrypi4_defconfig
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or for model 4 B (64 bit):
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$ make raspberrypi4_64_defconfig
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For model CM4 (on IO Board):
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$ make raspberrypicm4io_defconfig
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or for CM4 (on IO Board - 64 bit):
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$ make raspberrypicm4io_64_defconfig
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Build the rootfs
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----------------
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Note: you will need to have access to the network, since Buildroot will
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download the packages' sources.
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You may now build your rootfs with:
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$ make
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(This may take a while, consider getting yourself a coffee ;-) )
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Result of the build
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-------------------
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After building, you should obtain this tree:
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output/images/
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+-- bcm2708-rpi-b.dtb [1]
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+-- bcm2708-rpi-b-plus.dtb [1]
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+-- bcm2709-rpi-2-b.dtb [1]
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+-- bcm2710-rpi-3-b.dtb [1]
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+-- bcm2710-rpi-3-b-plus.dtb [1]
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+-- bcm2711-rpi-4-b.dtb [1]
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+-- bcm2711-rpi-cm4.dtb [1]
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+-- boot.vfat
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+-- rootfs.ext4
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+-- rpi-firmware/
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| +-- bootcode.bin
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| +-- cmdline.txt
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| +-- config.txt
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| +-- fixup.dat [1]
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| +-- fixup4.dat [1]
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| +-- start.elf [1]
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| +-- start4.elf [1]
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| `-- overlays/ [2]
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+-- sdcard.img
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+-- Image [1]
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`-- zImage [1]
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[1] Not all of them will be present, depending on the RaspberryPi
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model you are using.
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[2] Only for the Raspberry Pi 3/4 Models (overlay miniuart-bt is needed
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to enable the RPi3 serial console otherwise occupied by the bluetooth
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chip). Alternative would be to disable the serial console in cmdline.txt
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and /etc/inittab.
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How to write the SD card
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========================
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Once the build process is finished you will have an image called "sdcard.img"
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in the output/images/ directory.
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Copy the bootable "sdcard.img" onto an SD card with "dd":
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$ sudo dd if=output/images/sdcard.img of=/dev/sdX
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Insert the SDcard into your Raspberry Pi, and power it up. Your new system
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should come up now and start two consoles: one on the serial port on
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the P1 header, one on the HDMI output where you can login using a USB
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keyboard.
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How to write to CM4 eMMC memory
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===============================
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For CM4 modules without eMMC memory see above for booting from SD card,
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for CM4 moduels with eMMC memory proceed as following:
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- fit jumper on IO Board header J2 to disable eMMC boot
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- connect IO Board micro USB port (J11 USB slave) to your host linux system
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- power up CM4/IO Board (lsusb command should show a '0a5c:2711 Broadcom Corp.
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BCM2711 Boot' device)
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- run 'sudo ./host/bin/rpiboot', output should look like the following:
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Waiting for BCM2835/6/7/2711...
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Loading embedded: bootcode4.bin
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Sending bootcode.bin
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Successful read 4 bytes
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Waiting for BCM2835/6/7/2711...
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Loading embedded: bootcode4.bin
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Second stage boot server
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Loading embedded: start4.elf
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File read: start4.elf
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Second stage boot server done
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- a USB mass storage device should show up (the CM4 eMMC memory), proceed
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as described above to copy sdcard.img to it
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- power down CM4/IO Board
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- remove jumper on IO Board header J2 to re-enable eMMC boot
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- power up CM4/IO Board
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