What is the reference voltage used by AnalogIn() on the mDot?

[Frank A]

Hi,

I am currently experimenting with the mDot, and I was wondering what is the reference voltage used by AnalogIn() in mbed. Is it 3.3V or 3.0V? If it’s 3.0V, does it mean that using a voltage source greater than 3.0V (i.e. between 3.3V and 5.0V) into the analog pin (in “input mode”) could damage the mDot?

I read a few tutorials on ARM mbed’s website about AnalogIn(), and those examples where talking about a 3.3V reference voltage, but those were for different modules (i.e. not the mDot), thus the confusion. But from looking at page 26 of the mDot developer guide, I understand that pin 24 (named Vout/Vref) outputs 3.0V @25ma, so I guess that one of the main purposes of that pin is to be used with analog inputs, which suggests that the analog inputs on the mDot use 3.0V as a reference voltage. Is that correct?

Thank you for your time and support. A+

Frank

• This topic was modified 7 years, 11 months ago by Frank A.
• This topic was modified 7 years, 11 months ago by Frank A.
• This topic was modified 7 years, 11 months ago by Frank A.
• This topic was modified 7 years, 11 months ago by Frank A.

[Frank A]

Hi,

I just stumbled upon this thread on this forum, in which it is mentioned that the mDot’s reference voltage for analog inputs is indeed 3V. So I guess this does answer part of my original question, but could this please be confirmed with a quick reply?

That being said, the last part of my initial question is: Is pin 24 of the mDot intended to be used (among other things), for instance, to help power analog sensors (e.g. pin 20 in analog input mode; AnalogIn(A0))?

Thank you for your time and support.

Frank

[Peter Ferland]

Pin 24 is connected to ADC voltage supply input, which is tied to an on board regulated 3V source. You can use it for sensors up to that 25mA limit.

[Frank A]

Thank you for confirming this Peter. A+ 🙂

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