How to modify a Stern SPIKE SD card & install the MPF SPIKE bridge

1. Backup the existing SD card

When you download firmware updates from Stern’s websites to a USB stick, the updates only contain the specific parts of the code that have changed since the original version.

In other words, if you break or somehow screw up the SD card with the SPIKE game code on it, you will not be able to fix it by re-downloading the latest firmware. (You’ll have to call Stern and get a new SD card with the software already on it.)

So be very careful here.

Our recommendation is to create an image of the original SD card, and then put the original in a safe place and then copy the image to a new SD card. That way you’re always working with a copy and the original SD card is never touched.

Note that we do not yet know which cards are best or will be fully compatible, so our recommendation is to get a card that’s around the same size as the current one. Let us know what you find in terms of what works and what doesn’t!

Known SD Cards that work: SanDisk Ultra Plus 16GB purchased from Best Buy

One tool you can use to backup an image of your SD Card is HDD Raw Copy. This tool will back up a copy to your local drive and you can restore it to the new SD card. For a tutorial on backing up your Stern SD card using HDD Copy check out the following video.


Save a copy of your SD card image in case you need to restore your SD card. If, at one point, your SD memory card becames corrupted, restoring from the backed up image fixes the issue.

2. Mount the SD card

You need to mount the Linux root partition (which is probably #3).

On Windows you need an additional tools to mount ext3. We got a report that “Paragon ExtFS for Windows” works fine for this.

On Mac OS X, the tool “FUSE-ext2” is an option. You will most likely need to use sudo, and depending on your configuration the appropriate disk device may vary. In the following example, the Linux root is on partition 3 of the SD card, which is disk2:

sudo fuse-ext2 /dev/disk2s3 /Volumes/SD -o force

3. Edit /etc/inittab

Last line needs to be changed to enable login without a password:

S0:2345:respawn:/sbin/getty 115200 ttyS0 -n -l /bin/sh

Furthermore, you might want to add this line to allow USB login (e.g. if your board does not have DBGU populated).

USB0:2345:respawn:/sbin/getty 115200 ttyUSB0 -n -l /bin/sh

4. Edit /etc/rc2.d/S95game

Add the following line as the new second line in this file:

exit 1

This causes this script to exit instead of running the original Stern game code. (You can remove this line again if you want to run the original game again.)

5. Install the spike bridge

Add mpf-spike-bridge to /bin/bridge and mark it as executable.

On Linux this can be done with chmod +x bridge from within the folder.

Get the bridge from

Note that we have a precompiled binary in there (as well as the C source code).


It might be hard to mark the bridge binary as executable on Windows (but should be possible). If you cannot do this proceed to the next step and afterwards do the following:

  1. Download PuTTY from PuTTY is a free telnet app that allows you to remotely connect to the Linux OS running on the SPIKE system. PuTTY was also useful for verifying the connection from your Windows machine to the Linux OS running on SPIKE.
  2. In PuTTY, select the “Serial” buttont, change to correct COM (COM1, COM3, COM4, etc) port and set speed to 115200 baud. If you are unsure of which COM port Windows used when you plugged in your cable, open the Device Manager in the Control Panel. Click open the PORTS drop down to find which COM port is in use.
  3. Power up spike
  4. Press enter and you should get a command promt (if not, your serial connection is probably not working).
  5. Type the following:
mount -o remount,rw /
chmod +x /bin/bridge
mount -o remount,ro /


On OS X with fuse-ext2, overwriting files can fail without a message. When updating mpf-spike-bridge, you may want to remove the old bridge file before copying the new one.

rm <sd_mount>/bin/bridge cp <your_path>/mpf-spike-bridge/bridge <sd_mount>/bin/bridge chmod 755 <sd_mount>/bin/bridge

6. Unmount the SD card. Put it back in your spike system

Unmount the card. Really! Do that! Spike will not boot from a corrupted filesystem. SD cards may need a while to write everything. Give them those extra 10s. This is particularly important on Windows. If the red LED in the middle of the Stern CPU board is not blinking your SD card may be corrupt.


The SD card can become corrupted when removing the card without ejecting it properly. You can fix this by restoring your backup from above.

Now when you power up the pinball machine, instead of running the original game code, it will run the spike bridge which will listen for commands from the CN2 connector and will send out information about the state of the machine via that connector.