Working with SD cards

Written by Pat Hanrahan

SDHC card

Your Raspberry Pi kit contains a Kingston SDHC card. A secure digital (SD) card contains non-volatile memory for storage. The HC in SDHC stands for high capacity.

Kingston SDHC Card

The Raspberry Pi runs the software on the SDHC card installed in the SD card holder on the bottom of the printed circuit board.


Mounting the SDHC Card in your laptop

Most laptops contain a SD slot. You need to insert the SDHC card into your laptop, and mount the file system.

SDHC holder

When you insert the SDHC card it should mount automatically. You should see it show up in your finder along with other mounted file systems.

SD Finder

Verify that the card is mounted.

% ls /Volumes
Macintosh HD    NO NAME

By default, the volume is named NO NAME.

Download and install firmware

Now, download the Raspberry Pi firmware from our Github repository.

There should be 4 files.

% ls firmware
blink-actled.bin   bootcode.bin     bootloader.bin  start.elf     

bootcode.bin is the bootloader for the GPU and start.elf is the GPU start up code. Normally, kernel.img is the linux kernel. In this course, we will run replace the linux kernel with our own program.

Notice there are also two programs, blink-actled.bin and bootloader.bin. Initially, you should just copy blink-actled.bin to kernel.img. Thus, when the Pi boots, it runs a program that blinks the on-board activity (ACT) LED connected to GPIO47. This is a good way to test whether your Pi is working. If instead, you replace kernel.img with bootloader.bin, the Pi will boot and run a boot loader that can be used to upload programs to the Pi. You should replace kernel.img with bootloader.bin after you’ve tested that your Pi works correctly with blink-actled.bin.

Copy these files onto your SDHC Card.

Eject your SDHC card

On the Mac, go to the finder and click on the Eject icon next to the file name.

On linux, …


  1. The SDHC cards we are using are formatted with a FAT32 filesystem. If this file system is corrupted, you will need to reformat the file system. Consult the internet for how to do this.
  2. The Raspberry Pi can become wedged if kernel.img has bugs or becomes corrupted. You can always recover to a known state by copying the original firmware to the SDHC card.