Update README.md

README.md

@@ -4,3 +4,18 @@ Custom PCB with SAMD21 QT PY controlling TWO ADG1606BRUZ 16 input muxes!
 ![picture](https://github.com/charkster/mux_board_v3/blob/main/mux_board_v3_pcb.png)
 
 Check-out my **PDF** [schematic](https://github.com/charkster/mux_board_v3/blob/main/mux_board_v3_schematic.pdf) !!
+
+The SAMD21 QT PY can be  programmed with the qt_py_samd21-usbtmc.uf2 file (drag-n-drop) and has the same USBTMC commands that my [Mux Board V1](https://github.com/charkster/mux_board_v1) had. Here is the list:
+
+**MUX1:EN 1** # enable MUX1, a zero will disable the mux
+
+**MUX1:SEL 1** # select S1 input, values 1 through 16 are valid
+
+**MUX1:EN?** # this query returns the state of MUX1
+
+**MUX1:SEL?** # this query returns the presently selected input
+
+***RST** # disables all MUX enables and sets DAC to 0V
+
+***IDN?** # returns valid commands and this URL
+