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AH: Set Headphone Volume

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, read the overview of how FSP works and how to connect first.

The AH: command is used to set the headphone volume of the FAST Audio Interface Board. The volume level is a value between 0x00 and 0x3f (decimal 0-63). The mode of the audio system can affect the headphone behavior. See the AM: command for details. Depending on the mode set, the headphone can be set up to be a line out. In this case, the AH command will have no effect. Same for if the mode is set to mute the headphone.

Command Syntax

AH:<DATA><CR>

Data is a a volume value from 00 to 3F (0-63)

The return value is the same as what was passed in.

The command AH:18<CR> will return AH:18<CR>, confirming the headphone volume was set to 18 hex, which is 24 decimal, or about 38% volume (24/63).

If the mode of the headphone is set to AUDIO_HEADPHONE_MODE_DUCK (see AM: command) the set headphone volume will increase or decrease over time based on the new settings. In AUDIO_HEADPHONE_MODE_DUCK mode, headphone volume is controlled by the audio system to cross fade between the main amps and the headphone amp when the headphones are detected.

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 brian@fastpinball.com. Thanks!

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