Merge pull request wled#2261 from AK5nowman/overlayum

Basic Usermod Overlay support & Seven Segment UM

Author: blazoncek

usermods/seven_segment_display/readme.md

@@ -0,0 +1,55 @@
+# Seven Segment Display
+
+Usermod that uses the overlay feature to create a configurable seven segment display.  
+This has only been tested on a single configuration. Colon support is entirely  untested. 
+
+## Installation
+
+Add the compile-time option `-D USERMOD_SEVEN_SEGMENT` to your `platformio.ini` (or `platformio_override.ini`) or use `#define USERMOD_SEVEN_SEGMENT` in `my_config.h`.
+
+## Settings
+Settings can be controlled through both the usermod setting page and through MQTT with a raw payload.
+##### Example
+ Topic ```<mqttDeviceTopic||mqttGroupTopic>/sevenSeg/perSegment/set```  
+ Payload ```3```
+#### perSegment -- ssLEDPerSegment
+The number of individual LEDs per segment. There are 7 segments per digit.  
+#### perPeriod -- ssLEDPerPeriod
+The number of individual LEDs per period. A ':' has 2x periods.
+#### startIdx -- ssStartLED
+Index of the LED that the display starts at. Allows a seven segment display to be in the middle of a string.
+#### timeEnable -- ssTimeEnabled
+When true, when displayMask is configured for a time output and no message is set the time will  be displayed.
+#### scrollSpd -- ssScrollSpeed
+Time, in milliseconds, between message shifts when the length of displayMsg exceeds the length of the displayMask.
+#### displayMask -- ssDisplayMask
+This should represent the configuration of the physical display. 
+<pre>
+HH - 0-23. hh - 1-12, kk - 1-24 hours  
+MM or mm - 0-59 minutes  
+SS or ss = 0-59 seconds  
+: for a colon  
+All others for alpha numeric, (will be blank when displaying time)
+</pre>
+##### Example
+```HHMMSS ```  
+```hh:MM:SS ```
+#### displayMsg -- ssDisplayMessage
+Message to be displayed across the display. If the length exceeds the length of the displayMask the message will scroll at scrollSpd. To 'remove' a message or revert  back to time, if timeEnabled is true, set the message to '~'.
+#### displayCfg -- ssDisplayConfig
+The order that your LEDs are configured. All seven segments in the display need to be wired the same way.
+<pre>
+           -------
+         /   A   /          0 - EDCGFAB
+        / F     / B         1 - EDCBAFG
+       /       /            2 - GCDEFAB
+       -------              3 - GBAFEDC
+     /   G   /              4 - FABGEDC
+    / E     / C             5 - FABCDEG
+   /       /
+   -------
+      D
+</pre>
+
+## Version
+20211009 - Initial release