update notes

git-svn-id: https://bucket.mit.edu/svn/nilm/zoom@6662 ddd99763-3ecb-0310-9145-efcb8ce7c51f

notes-a6302.txt

@@ -33,11 +33,11 @@ PIC measurements:
 
 --
 
-1 bit change at DAC is 1.2mA.
-At PIC, the voltage will change by (1.2mA * 10mV/mA * 4.32) = 0.518 mV
-This means changing 1 bit at the DAC should cause the PIC count to change by
-0.518 mV / (2.50 / 2^12) = 84.935
+1 bit change at full 16-bit DAC resolution is 0.3mA.
+At PIC, the voltage will change by (0.3mA * 10mV/mA * 4.32) = 12.96 mV
+This means changing 1 bit at the DAC should cause the 12-bit ADC count to change by
+12.96 mV / (250mV / 2^12) = 212.34
 
 To reset the PIC input to 2048, we therefore need to step the DAC by 
-((2048 - count) / 84.935)
+((2048 - count) / 212.34)