mention USB data rate

docs/tech-notes.md

@@ -7,6 +7,35 @@ so that when original sources fall off the net,
 hopefully at least my notes will still be around.
 
 
+USB data rate
+-------------
+
+Unlike the Santroller
+(which is much easier to install for beginners),
+this firmware does not send continuous updates over USB,
+unless it has to.
+
+Because the only analog input is the wammy bar,
+if you don't include that input,
+the controller can stay silent until a button is pressed or released.
+This allows 4 controllers to connect to a USB hub,
+with no concern for overwhelming the hub.
+Since the amount of data is about the same as a keyboard,
+and a little less than a mouse,
+I would expect that a 7-port USB 2 hub would also handle 7 instruments,
+no problem.
+I just don't know of any games that can use mor than 4 instruments.
+
+If you do use the wammy bar,
+an update is sent every 20 milliseconds.
+The firmware still attempts to reduce lag
+by sending button change events as soon as possible.
+I haven't played with this much,
+so if you have a wammy bar set up,
+please reach out to me and let me know how it works.
+
+
+
 Sample Rate
 -----------