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SL: Configure a switch

FAST Serial Protocol: Overview & First Steps

This documentation section is about the FAST Serial Protocol (FSP) commands, which are the low-level commands a host computer sends to a FAST board. Most FAST Pinball makers do not need to know about these details, since the pinball game framework (such as the Mission Pinball Framework) handles this communication for you.

If you're writing your own game framework, we have a series of programming guides. Also, be sure to read the overview of how FSP works and how to connect first.

The SL: command is used to configure a switch, which includes debounce times and how switch changes are reported to the host computer.

Nano Controllers use N instead

The FAST Nano Controller uses the letter N for switch & driver-related commands instead of L. So everything here applies to the Nano too, except the commands are -N: /N: SN: DN: QN:.

Command usage:



Any switch ID number, in hex.


  • 0 Do not report any switch state changes to the host computer.
  • 1 Report normally.
  • 2 Report inverted, for "normally closed" (NC) or opto switches.


Time to debounce switch close in ms. Default 2 ms (02 hex). 256 ms max (range 00-FF hex).


Time to debounce switch open in mS. Default 20 ms (14 hex). 256 ms max (range 00-FF hex).



Set switch 0x02 to report normal, debounce close time is 32 ms (20 hex), Debounce open time is 16 ms (10 hex).



Documentation Feedback? Requests? Confused?

Hi! I'm Brian, and I'm responsible for the documentation at FAST Pinball. If you have any feedback, requests, corrections, ideas, or any other thoughts about this documentation, please let me know! You can email me at Thanks!

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