Added readme for PWM fan usermod.

usermods/PWM_fan/readme.md

@@ -0,0 +1,36 @@
+# PWM fan
+
+v2 Usermod to to control PWM fan with RPM feedback and temperature control
+
+This usermod requires Dallas Temperature usermod to obtain temperature information. If this is not available the fan will always run at 100% speed.
+If the fan does not have _tacho_ (RPM) output you can set the _tacho-pin_ to -1 to not use that feature.
+
+You can also set the thershold temperature at which fan runs at lowest speed. If the actual temperature measured will be 3°C greater than threshold temperature the fan will run at 100%.
+
+If the _tacho_ is supported the current speed (in RPM) will be repored in WLED Info page.
+
+## Installation
+
+Add the compile-time option `-D USERMOD_PWM_FAN` to your `platformio.ini` (or `platformio_override.ini`) or use `#define USERMOD_PWM_FAN` in `myconfig.h`.
+You will also need `-D USERMOD_DALLASTEMPERATURE`.
+
+### Define Your Options
+
+All of the parameters are configured during run-time using Usermods settings page.
+This includes:
+
+* PWM output pin
+* tacho input pin
+* sampling frequency in seconds
+* threshold temperature in degees C
+
+_NOTE:_ You may also need to tweak Dallas Temperature usermod sampling frequency to match PWM fan sampling frequency.
+
+### PlatformIO requirements
+
+No special requirements.
+
+## Change Log
+
+2021-10
+* First public release

usermods/PWM_fan/usermod_PWM_fan.h

@@ -6,7 +6,7 @@
 
 #include "wled.h"
 
-// PWM code curtesy of @KlausMu
+// PWM & tacho code curtesy of @KlausMu
 // https://github.com/KlausMu/esp32-fan-controller/tree/main/src
 // adapted for WLED usermod by @blazoncek
 
@@ -44,7 +44,7 @@ class PWMFanUsermod : public Usermod {
     // configurable parameters
     int8_t  tachoPin          = -1;
     int8_t  pwmPin            = -1;
-    uint8_t tachoUpdateSec    = 5;
+    uint8_t tachoUpdateSec    = 30;
     float   targetTemperature = 25.0;
 
     // strings to reduce flash memory usage (used more than twice)
@@ -205,6 +205,7 @@ class PWMFanUsermod : public Usermod {
      * Below it is shown how this could be used for e.g. a light sensor
      */
     void addToJsonInfo(JsonObject& root) {
+      if (tachoPin < 0) return;
       JsonObject user = root["u"];
       if (user.isNull()) user = root.createNestedObject("u");
       JsonArray data = user.createNestedArray(FPSTR(_name));