[mBed] Why can P0.00 not be used as an AnalogIn?

[Hieu]

While both P0.00 and P0.01 has Analog Input function, initializing an AnalogIn (in mbed) with P0.00 will cause the firmware to fail to start at all; but initializing using P0.01 does not cause any issue.

Why is this the case? Is it because P0.00 is an ADC reference input, while P0.01 is an ADC input?

[Ole Bauck]

P0.00 is ADC reference input and not an ADC input. AIN0-AIN7 (P0.26-P0.27 + P0.01-P0.06) are the ADC inputs you can choose from, see Product Specification chapter 2.2. AIN0 and AIN1 is also used for 32KHz crystal, so if these shall be used the 32KHz crystal must be diconnected first.