update and link fast aud processor documentation, document exp_int feature, and link root fast config docs to fast website

Author: bosh

docs/config/fast.md

@@ -17,7 +17,7 @@ title: "fast: Config Reference"
 The following config documentation is relevant for MPF 0.57.4 and 0.80.0. Last updated Dec 18, 2025.
 
 The `fast:` section of your machine-wide config is where you configure hardware options that are specific to the FAST Pinball Controller.
-There is [a guide in "Hardware"](../hardware/fast/index.md) which includes FAST-specific settings and device configuration examples.
+The [FAST website](https://fastpinball.com/mpf/config/) also has thorough documentation and examples for MPF 0.57 and 0.80 compatible configurations.
 
 ## fast: config reference
 

docs/config/fast/fast_aud.md

@@ -14,3 +14,54 @@ title: "fast:aud: Config Reference"
 ## aud: config reference
 
 Within the `fast:` section of your machine-wide config, you configure the audio board processor in the subsection `aud:`.
+
+### Sample config:
+
+```yaml
+fast:
+  aud:
+    port: auto
+    main_amp_enabled: true
+    sub_amp_enabled: true
+    headphones_amp_enabled: true
+
+    main_steps: 20
+    sub_steps: 20
+    headphones_steps: 20
+
+    default_main_volume: 32
+    default_sub_volume: 32
+    default_headphones_volume: 16
+
+    persist_volume_settings: true
+
+    max_hw_volume_main: 63
+    max_hw_volume_sub: 63
+    max_hw_volume_headphones: 63
+
+    main_levels_list: None
+    sub_levels_list: None
+    headphones_levels_list: None
+
+    link_sub_to_main: true
+    link_headphones_to_main: false
+
+    headphones_level: headphones
+    mute_speakers_with_headphones: true
+```
+
+### port:
+
+List of one (or more) values, each is a type: `string`. Defaults to `auto`.
+
+A comma-separated list of the serial port names your FAST controller uses.
+
+### baud:
+
+Single value, int, default: `230400`
+
+The connection baud rate.
+
+### FAST Docs:
+
+For the other properties, see the [FAST Audio Interface MPF Config page](https://fastpinball.com/mpf/config/audio/).

docs/config/fast/fast_exp.md

@@ -14,3 +14,62 @@ title: "fast:exp: Config Reference"
 ## exp: config reference
 
 Within the `fast:` section of your machine-wide config, you configure the EXP processor in the subsection `exp:`, and sometimes in `exp_int`.
+
+### port:
+
+List of one (or more) values, each is a type: `string`. Defaults to `auto`.
+
+A comma-separated list of the serial port names your FAST controller uses.
+
+### baud:
+
+Single value, int, default: `921600`
+
+The connection baud rate.
+
+### boards:
+
+Dict of string board names to dicts of EXP board properties. Defaults to empty.
+
+Example:
+
+```yaml
+fast:
+  exp:
+    port: auto
+    boards:
+      neuron:
+        model: FP-EXP-2000
+      playfield_0081:
+        model: FP-EXP-0081
+```
+
+#### model:
+
+The product number of the IO board. E.G. `FP-EXP-0081`
+
+#### ignore_led_errors:
+
+Single value, boolean, default: `false`
+
+If false, LED hex communication decode errors will be raised as errors when encountered from this board.
+If you encounter instability due to these errors, set this to true to silently ignore them.
+
+## Using exp_int
+
+If using a Raspberry Pi connected directly to the Neuron controller, the LED headers on the Neuron will not be available on the normal EXP interface.
+In order to access these Neuron LED headers, you must define a parallel structure to the existing `exp:` configuration, and move the Neuron definition over to it.
+
+Example:
+
+```yaml
+fast:
+  exp:
+    boards:
+      playfield_0081:
+        model: FP-EXP-0081
+  exp_int:
+    boards:
+      neuron:
+        model: FP-EXP-2000
+```