Working with SD cards

Written by Pat Hanrahan

Using the SD card

Your Raspberry Pi kit contains a Kingston microSDHC 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 microSDHC card installed in the card holder on the bottom of the printed circuit board.


Mounting the SDHC Card in your laptop

Most laptops contain a SD slot. To copy software to the card, you need to mount it on your laptop. To do this, insert the microSDHC card into the SD card holder, and then insert the holder into your laptop’s SD card slot.

SDHC holder

When you insert the SD 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 files from our courseware 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 replace the linux kernel with our own program to run.

We have included two programs, blink-actled.bin and bootloader.bin. Initially, you should copy blink-actled.bin to kernel.img. Thus, when the Pi boots, this program will blink the on-board activity (ACT) LED. 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 SD Card.

Eject your SD card

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


  1. The SD 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 SD card.