---

description: This document describes the steps to setup Raspberry Pi 4 for running BK

---

# Set up Raspberry Pi 4 to run BK

To run BK on Raspberry Pi, we need several steps to set up your hardware

## Pre-requisites

- Raspberry Pi 4
- TTL to USB cable
- micro SD card
- USB type A to type C cable (or power cable)

## Format SD card

To boot from an SD card, we need to install Raspberry Pi firmware.

The simplest way to do it is to use [Raspberry Pi Imager](https://www.raspberrypi.org/software/).

You can select `Raspberry Pi OS Lite (32 bit)` image and click write to start the installation.

After formatting the SD card, enter the boot section of the card, append the following lines to `config.txt`.

core_freq_min=500
enable_uart=1

## Connect to UART

Connect the TTL cable to the corresponding pins on Raspberry Pi:
- `GND` to `6` pin
- `RX` to `8` pin
- `TX` to `10` pin

You can check the pinout at [UART at Raspberry Pi GPIO Pinout](https://pinout.xyz/pinout/uart).

Then we can power up the Raspberry Pi and open the UART output.
If it boots successfully, we will see the output like the following:

<...>

[    3.176335] Segment Routing with IPv6
[    3.214711] systemd[1]: systemd 241 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-hierarchy=hybrid)
[    3.237254] systemd[1]: Detected architecture arm64.
[    3.267411] systemd[1]: Set hostname to <raspberrypi>.
[    3.828087] random: systemd: uninitialized urandom read (16 bytes read)
[    3.846401] random: systemd: uninitialized urandom read (16 bytes read)
[    3.854305] systemd[1]: Listening on Journal Socket.
[    3.860399] random: systemd: uninitialized urandom read (16 bytes read)
[    3.872492] systemd[1]: Mounting Kernel Debug File System...
[    3.883067] systemd[1]: Starting Create list of required static device nodes for the current kernel...
[    3.894427] systemd[1]: Created slice User and Session Slice.
[    3.901770] systemd[1]: Listening on fsck to fsckd communication Socket.
[    3.909961] systemd[1]: Listening on Syslog Socket.
[    3.920163] systemd[1]: Starting Set the console keyboard layout...

Raspbian GNU/Linux 10 raspberrypi ttyS0

raspberrypi login:

We now know that the setting and the UART works. In the next step, we will replace Raspberry Pi OS with BK image.

## Boot BK

In the beginning, we need to compile an executable

$ cmake . -DBUILD_PLATFORM=raspi4
$ make yielding

Translate the ELF file into an image.

$ aarch64-none-elf-objcopy -O binary demos/yielding/yielding kernel8.img

Now, plug in the SD card to your computer, delete all `kernel*.img` in the boot section, copy `kernel8.img` we made before into that section.

Then plug the SD into the Raspberry Pi and power up.
If it works, you will see the output just like the one on QEMU.

Thread            0: working
Thread            0: yielding
Thread  <scheduler>: scheduling new thread
Thread  <scheduler>: next thread chosen
Thread            1: yielding
Thread  <scheduler>: scheduling new thread
Thread  <scheduler>: next thread chosen
Thread            0: resuming
Thread            0: working
Thread            0: yielding
Thread  <scheduler>: scheduling new thread
Thread  <scheduler>: next thread chosen
Thread            1: resuming
Thread            1: yielding
Thread  <scheduler>: scheduling new thread
Thread  <scheduler>: next thread chosen
Thread            0: resuming
Thread            0: working
Thread            0: yielding
Thread  <scheduler>: scheduling new thread
Thread  <scheduler>: next thread chosen
Thread            1: resuming
Thread            1: working
Thread            1: exiting
Exiting kernel

###### tags: `AMT`