This application is a digital voltmeter reading the ADC and displaying the
result on the MDM-1.

In this application the Vref+ is the supply voltage (+4.95V on my sample) and
Vref- is 0V. Scaling is 4.88mV per division but there will be some error
depending on the exact value of the supply.  In real life it is better to use
a reference of say 4.096V as the ADC has 10bit resolution (1024 steps) then each step
is of equal value and calibration is not dependant on the setting of the power supply.

The checksum of the code is 485C.

