Timesys Getting Started Guide for Raspberry Pi 3

Introduction
Prerequisites
- Host Requirements
- Target Requirements
Preparing the Target
- Configuring Serial Communication
- Preparing the Secure Digital Card
Preparing the Host
Booting the Board
Additional Information
- Linux console on GPIO header
- Factory Documentation

Introduction

This document will describe in detail the procedures for booting a Linux kernel image and mounting a root file system from an SD Card on the Raspberry Pi 3.

Prerequisites

Host Requirements

To properly boot the Raspberry Pi 3 using software from Timesys, your host machine must meet the following requirements:

Modern GNU/Linux Distribution. Timesys recommends one of the following distributions:
- Ubuntu (Most recent release or LTS)
- Fedora (Most recent release)
Root or sudo permission on the Development Host.
A copy of the Linux Kernel (zImage-4.19-ts-armv7l) and Root File System (rootfs.tar.gz) for the Target Board downloaded from Factory. These are found in the output directory of your online build, or in the directory build_armv7l-timesys-linux-<libc>/images/ on the command line.
An available USB port on your Development Host.
A SD card slot or adapter on your Development Host.

Target Requirements

To boot the Raspberry Pi 3, you will need the following items:

Raspberry Pi 3
SD Card
Micro USB Cable

Once you have all of the necessary components, you should perform the following steps:

Connect the power supply to your board.
Set aside the SD card, you will need to intialize it from the Development Host before booting the board.

Preparing the Target

Configuring Serial Communication

The Raspberry Pi 3 uses a serial debug port to communicate with the host machine. The commands discussed in this section are meant to be performed by a privileged user account. This requires the root login or prepending each command with sudo.

Using Minicom

Start minicom on your host machine in configuration mode. As root:

# minicom -o -s -w
A menu of configuration should appear. Use the Down-arrow key to scroll down and select the Serial port setup option, and press Enter.
Verify that the listed serial port is the same one that is connected to the target board. If it is not, press A, and enter the correct device. This is /dev/ttyUSB0 on most Linux distributions.
Set the Bps/Par/Bits option by pressing the letter E and using the next menu to set the appropriate values. You press the key that corresponds to the value 115200, then press Enter.
Set Hardware flow control to No using the F key.
Set Software flow control to No using the G key.
Press Enter to return to the main configuration menu, and then press Esc to exit this menu.
Reset the board, and wait for a moment. If you do not see output from the board, press Enter several times until you see the prompt. If you do not see any output from the board, and have verified that the serial terminal connection is setup correctly, contact your board vendor.

TIP: If you experience an error similar to Device /dev/ttyUSB0 is locked when starting minicom, it usually means that another process is using the serial port (which is usually another instance of minicom). You can find the process that is currently using the serial port by executing the following:

# fuser /dev/ttyUSB0 /dev/ttyUSB0: 28358

# ps 28358 PID TTY STAT TIME COMMAND 28923 pts/0 S+ 0:00 minicom

This process can also be killed directly with fuser as root. Please use this command with caution:

# fuser -k /dev/ttyUSB0

Using GNU Screen

To quickly connect to a board using Gnu Screen, execute the following:

# screen /dev/ttyUSB0 115200

For more information about using screen, please consult the man page, or view the manual online at http://www.gnu.org/software/screen/manual/screen.html

Preparing the Secure Digital Card

The Raspberry Pi 3 boots from an SD card. Some kits may be shipped with one that contains a sample kernel and RFS preloaded. We will be replacing these with the kernel and RFS from Factory. If you are using a blank SD card or have trouble replacing the software on the preloaded one, see Partitioning the SD Card. Otherwise, skip directly to Writing Boot Files to the SD Card.

Before you begin, you should determine the name of your SD card on your host system. To do so:

Connect the SD card to your host system. Many modern systems have SD card slots on the case, or you can purchase a USB SD Card Reader for around $15 US.
Determine the device name of the SD Card. This can be done using dmesg. In the following example, the device is /dev/sdX, which contains one partition sdX1.

$ dmesg | tail [88050.184080] sd 4:0:0:0: [sdX] 1990656 512-byte hardware sectors: (1.01 GB/972 MiB) [88050.184821] sd 4:0:0:0: [sdX] Write Protect is off [88050.184824] sd 4:0:0:0: [sdX] Mode Sense: 03 00 00 00 [88050.184827] sd 4:0:0:0: [sdX] Assuming drive cache: write through [88050.185575] sd 4:0:0:0: [sdX] 1990656 512-byte hardware sectors: (1.01 GB/972 MiB) [88050.186323] sd 4:0:0:0: [sdX] Write Protect is off [88050.186325] sd 4:0:0:0: [sdX] Mode Sense: 03 00 00 00 [88050.186327] sd 4:0:0:0: [sdX] Assuming drive cache: write through [88050.186330] sdX: sdX1

Partitioning the SD card

If you want to use a different SD card or its contents become corrupted, you can use the fdisk tool to create two partitions on your SD card. Please note that all data on the card will be lost upon completion of these steps.

Unmount the partition if it was automounted by using the umount command.
$ umount /dev/sdX1
As root, run the fdisk utility on the drive.
$ sudo fdisk /dev/sdX
In fdisk, Delete the existing partition table and create a new one using the o command.
Command (m for help): o Building a new DOS disklabel with disk identifier 0x8b025602. Changes will remain in memory only, until you decide to write them. After that, of course, the previous content won't be recoverable.
Create a new primary partition using the n command. The first partition will be a FAT partition for storing the boot files. 64 MB is typically more than enough for this purpose.
Command (m for help): n Partition type: p primary (0 primary, 0 extended, 4 free) e extended Select (default p): p Partition number (1-4, default 1): 1 First sector (2048-30679039, default 2048): Using default value 2048 Last sector, +sectors or +sizeK,M,G (2048-30679039, default 30679039): +64M
Set the first partition as W95 FAT32 (LBA) using the t command and entering the Hex code c.
Command (m for help): t Selected partition 1 Hex code (type L to list codes): c
Set the bootable flag on the first partition using the a command.

Command (m for help): a Partition number (1-4): 1
Create a second primary partition using the n command. This partition will be a linux partition for storing the root filesystem. It will fill the rest of the SD card.

Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4, default 2): 2 First sector (133120-30679039, default 133120): Using default value 18432 Last sector, +sectors or +sizeK,M,G (133120-30679039, default 30679039): Using default value 30679039
Verify that the partition table is correct by using the p command. It should look similar to the following:

Command (m for help): p Disk /dev/sdX: 15.7 GB, 15707668480 bytes 64 heads, 32 sectors/track, 14980 cylinders, total 30679040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x6eaae8f8 Device Boot Start End Blocks Id System /dev/sdX1 * 2048 133119 65536 c W95 FAT32 (LBA) /dev/sdX2 133120 30679039 14773960 83 Linux
This step will destroy all data on the SD Card - Write the partition table to the card using the w command.

Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. WARNING: If you have created or modified any DOS 6.x partitions, please see the fdisk manual page for additional information. Syncing disks.
Format the first partition of the SD card with a FAT filesystem using the mkfs.vfat tool.

$ sudo /sbin/mkfs.vfat -n boot /dev/sdX1
Format the second partition using an ext4 filesystem using the mkfs.ext4 tool.

$ sudo /sbin/mkfs.ext4 -L rfs /dev/sdX2

Writing Boot Files to the SD Card

Mount the partitions. You can remove and reinsert the card to trigger the automount, or you can use the mount command to mount the partition to an arbitrary location.

$ sudo mount /dev/sdX1 /media/boot $ sudo mount /dev/sdX2 /media/rfs
Copy the bootloader files into the vfat partition.

$ sudo cp start.elf /media/boot/ $ sudo cp bootcode.bin /media/boot/ $ sudo cp fixup.dat /media/boot/ $ sudo cp config.txt /media/boot/ $ sudo cp cmdline.txt /media/boot/
Copy the kernel image into the vfat partition as a file named kernel.img.

$ sudo cp zImage-4.19-ts-armv7l /media/boot/kernel.img
Copy the device tree blob into the vfat partition.

$ sudo cp raspberrypi3.dtb /media/boot/
As root, extract the rootfs.tar.gz archive to the RFS partition.

$ sudo tar xzf rootfs.tar.gz -C /media/rfs
Unmount both partitions before removing the card from the Development Host. Then place the card in the SD slot on the Raspberry Pi 3.

$ sudo umount /dev/sdX1 $ sudo umount /dev/sdX2

Preparing the Host

No additional host setup is required to boot from SD.

Booting the Board

The Raspberry Pi 3 should boot automatically once powered up.

Additional Information

Linux console on GPIO header

By default, Linux console will be available on tty1, can be accessed over the HDMI display. To enable Linux console on the UART transmit and receive pins GPIO 14 and GPIO 15 respectively, which are pins 8 and 10 on the GPIO header, append 'enable_uart=1' to the config.txt file and replace 'console=tty1' to 'console=ttyS0,115200' in the cmdline.txt file.