BUGS

HARDWARE/PCB
20140831-1 ADC Reference Voltage
The ADC cannot be used with the current external reference voltage.

According to Table 36-40 from the Xmega 32A4U device datasheet, the ADC
reference voltage must fulfill
    1V <= V_REF <= AVCC - 0.6V
As AVCC = 3.3V, the maximum V_REF = 2.7V.

Currently, the AREFA pin is connected to 3.3V, as well as the potentiometers
(voltage dividers).

Fix in SW:
Use INTVCC2 as REFSEL and differential with gain of 0.5.
This will set V_REF to 1.65V and scale the maximum poti value to 1.65V as well.

Severity:
Without fix, the ADC values are mostly useless.
With the fix, accuracy might be lowered because INTVCC2 likely is not as
accutate as the external AREFA, but overall it should be acceptable.

20140831-2 Duplicate output lines for LEDs
For example, the switch to toggle the LO signal has a nearby STATUS_LO LED.
When the software detects that the switch is pressed, it will toggle the active
low LO line for the UDN2596A voltage level shifter, as well as the LED.
Therefore, the logical signal/state "LO" is given twice: to the LED (active high)
and the level shifter (active low). It therefore consumes two IO pins.

The affected LEDs are:
- STATUS_LO
- STATUS_SOE
- STATUS_SODS
- STATUS_SUPPLY_CTRL (note: SUPPLY_CTRL line to MOSFET is active high!)

Fix in HW:
A next release of the PCB should connect the affected LEDs _in active low_ mode
to the output signal (level shifter). This simplifies the SW and frees one IO
pin per LED signal.

Severity: uncritical, fix in next PCB release