Update Reference.md

docs/Reference.md

@@ -63,6 +63,12 @@ The following **optional** `homeSpan` methods override various HomeSpan initiali
   * setting *suffix* to a null string "" is permitted.
   * example: `homeSpan.begin(Category::Fans, "Living Room Ceiling Fan", "LivingRoomFan");` will yield a default *hostName* of the form *LivingRoomFan-A1B2C3D4E5F6.local*.  Calling `homeSpan.setHostNameSuffix("v2")` prior to `homeSpan.begin()` will instead yield a *hostName* of *LivingRoomFanv2.local*
   
+* `void setQRID(const char *ID)`
+  * changes the Setup ID from the HomeSpan default ("HSPN") to *ID*
+  * *ID* must be exactly 4 alphanumeric characters.  If not, the request to change the Setup ID is silently ignored and remains "HSPN"
+  * The Setup ID is an optional parameter used when pairing the device to HomeKit with a QR Code (instead of the usual Setup Code)
+  
+  
 ## *SpanAccessory(uint32_t aid)*
 
 Creating an instance of this **class** adds a new HAP Accessory to the HomeSpan HAP Database.