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CI20-baremetal

This project is result of my attempt to learn low-level MIPS programming using the MIPS Creator CI20. It contains a number of bare-metal experiments inspired by the "Baking Pi - Operating Systems Development " course by Alex Chadwick at University of Cambridge:

THE EXPERIMENTS

The experiments are organized in directories numbered in chronological order:

  • 01_led - simplest possible example to access and turn on/off a LED
  • 02_delay - code to periodically turn the LED on and off
  • 03_function - same as 02, but the code is now organized in a number of functions
  • 04_rtc - same as 03, but the code is spread across multiple files. Uses RTC timer for the blinking time
  • 05_uart - uses UART to communicate with the board. Also, introduces C...

USAGE

REQUIREMENTS

You need the following components:

  1. A native GCC toolchain and utilities
  2. A GCC cross-compiler for MIPS
  3. The Linux mkimage utility
  4. A client for serial communication

On Ubuntu (and probably also debian) this means:

sudo apt-get install gcc gcc-mipsel-linux-gnu u-boot-tools minicom

You can also use a third party compiler such as this one, but then you must set the CROSS_COMPILE variable accordingly

BUILDING

From project root, execute:

make

The generated files are in the "build" directory. To look at the generated code enter a directory and run:

make show

CONNECT TO THE DEVICE

To connect to the device enter a directory and run:

make console

This assumes the device is on /dev/ttyUSB0. If not you can set it manually, for example:

make console DEVICE=dev/ttyACM0

UPLOADING

You have two options for getting your code into the device:

Temporary (from u-boot console):

  1. connect to the CI20 serial port and power up the board
  2. when you see "Hit any key to stop autoboot", press enter
  3. enter "loads"
  4. copy-paste contents of build/<name>.srec into the u-boot console
  5. enter "go 0x8001000"

Permanent (from SD card):

  1. insert a working Linux SD card for CI20
  2. backup the boot/vmlinux.img file
  3. copy build/<name>.img over boot/vmlinux.img
  4. safely eject the SD card and insert it into the CI 20
  5. power the board!

SIMULATING

There are currently no simulators for CI20, but you can always use QEMU for MIPS for general testing:

sudo apt-get install qemu-system-mips

To start qemu and gdb, run these two in separate terminals:

make qemu
make gdb

Note that the latter requires GDB for MIPS which is currently not available as an Ubuntu package...