Without any peripherals attached, the following readings were observed:
* ADC0: 0x03f* ADC1: 0x03f* ADC2: 0x03f* ADC3: 0x03f* ADC4: 0x03f* ADC5: 0x000* ADC6: 0x03f* ADC7: 0x000
Writing to these appears to have no effect, with the readings not changing.