Update README.md

Clock/README.md

@@ -10,6 +10,16 @@
 
 ![Hardware](https://github.com/oddwires/RP2040/blob/master/Clock/Images/IMG_1215.JPG)
 
+* Supported commands
+  * ?   - Help
+  * V   - Version info
+  * S   - Set time: Notation: HH:MM:SS or HH,MM,SS<br>
+HH can be either 12 or 24 hour notation.  e.g. '03:00:00' is the same as '15:00:00'<br>
+Delimiter can be either ':' or ','. e.g. '15:00:00' is the same as '15,00,00'<br>
+MM is in the range 0<=MM<=59<br>
+SS is in the range 0<=SS<=59<br>
+Leading zeros can be ommited. e.g. '1:2:3' is the same as '01:02:03'<br>
+Trailing parameters can be ommited, and will be set to zero. e.g. '12:15' is the same as '12:15:00' and '12' is the same as '12:00:00'
+
 * Limitations:
   * USB serial requires Windows (10 or later)
-  * The code is working, but is a cut down version of the Function Generator code. This has resulted in some redundant code + variables that need tidying up.