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QL: Driver Test Mode (Neuron & Retro)

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 QL: mode lets you step through your drivers one-by-one while observing the FAST driver ID number. This test pulses the driver for 15 ms at 50% PWM duty cycle, so first ensure your drivers can handle that duration and power.

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:.

This is an interactive command designed to be used via a terminal emulator.

Command Syntax


To use this command, you do NOT type Enter after the colon. Just type QL: and then use the Q, W, or Space to control the tests. Hit Enter to exit the test mode.


  • Q = Increase Driver Number
  • W = Decrease Driver Number
  • Space = Pulse the same driver again.

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!

N or > jump the next page, P or < for previous, search with S or ?