- img:images for readnotes
- hello:test arm-linux-gcc installed correctly
- options:practice arm-linux-gcc options
- led:light LED0 through GPIO
- led_c:LED0,LED2,LED4 to count 0~8 in C
- key_led:control LEDs through keys
- sdram:copy code to sdram to run
- MMU:create page table to virtual address mapped