Add Michele's explanation how to find which sensor is connected to the FPGA board

docs/desy20.txt

@@ -4,6 +4,10 @@ Camera: 3840x5120
     * In fact two lines returned simultaneously (in each payload). So, there is 8 channels per line and 640 payloads are transferred to complete 2 lines.
     * Actually, 641. There is always 1 extra payload which is just skipped in libufodecode (starting with C0)
     * Actually, 1 (last) payload is missing for the first two rows. So, total number of payloads is (3840/2) * (640 + 1) - 32
+
+ - Limitations
+    * Due to encoding, ROI should always start at even line and include even number of lines
+
     
 
 Triggering

docs/sensors.txt

@@ -0,0 +1,10 @@
+The UFO 20 MPixel has internal version of 0x6 --> register 9030
+The UFO 2/4 Mpixel --> has internal version of 0x5 --> register 9030 
+
+At level of electronics both 2 and 4 Mpixel camera are similar at level of CNOSIS and you cannot differentiate. 
+There is only one bit set to "1" for the 4 Mpixel for PETRA this set the speed grade of the clock on the control_reg[31] 
+
+When it is set to 1 --> 4 Mpixel camera @ 12 bits resolution. 
+The 2Mpixel --> was to 0 
+
+Please have a look in the default configuration of the camera in control_reg[31] = 1  --> this means 4 Mpixel