zhangqq/raspbootin

Simple boot-over-serial bootloader for the Raspberry Pi

raspbootin

Simple boot-over-serial bootloader for the Raspberry Pi

The Raspbootin repository contains 2 components: Raspbootin and Raspbootcom.

Raspbootin:

Raspbootin is the actual bootloader that you install on the SD Card for your Raspberry Pi. Copy the raspbootin/kernel.img in place of the kernel.img on the SD Card and you are ready for use.

Raspbootcom:

Raspbootcom is a simple boot server and terminal program for the other side of the serial connection. You need to run this on another computer, the one the serial port of your Raspberry Pi is conneted to. On start Raspbootcom is in terminal mode. Any input on stdin is passed to the Raspberry Pi and any reply from the Raspberry Pi is printed to stdout. The Raspbootin bootloader will send 3 breaks (0x03) over the serial connection when it wants to boot a kernel and Raspbootcom then switches into kernel sending mode, reads the kernel from disk and sends it to the Raspberry Pi. After that it goes back into terminal mode so you can see the output from the Raspberry Pi and interact with it.

The kernel is read fresh every time it is send so you do not need to restart Raspbootcom every time the kernel image changes. My Raspberry Pi gets its power over the serial connection so unplugging and repluging the USB serial converter is how it reboots. Raspbootcom also survives unplugging and replugging of an USB serial converter and will automatically reopen the device when you replug it.

Compiling:

The build system is verry simple and the only thing configurable is the location of the arm cross compiler. By default the raspbootin/Makefile assumes you build your cross-compiler with PREFIX = /usr/local/cross and TARGET = arm-none-eabi. If that is not the case then you can override by setting PREFIX or ARMGNU in your environment:

export PREFIX=/usr/local/cross export ARMGNU=${PREFIX}/bin/arm-none-eabi

Where ARMGNU is the prefix for the compiler to use, ${ARMGNU}-gcc and friends must exist.

Other than that simply type

make

and it will build both Raspbootin and Raspbootcom.

Usage:

• Copy the raspbootin/kernel.img to the SD Card for the Raspberry Pi.
• Run raspbootcom/raspbootcom /dev/ttyUSB0 /where/you/have/your/kernel.img.
• Turn on the Raspberry Pi.