How to differentiate between Analog and Digital Pins in an STM32 MCU?

Question

I am using an STM32F302C8 and while reading the datasheet I am unable to differentiate between analog and digital input pins I am on pages 34-42 of This datasheet.

I am porting over from Arduino Nano to STM32F302C8 and all I need are 3 Analog and 5 Digital Pins.

• Justme: Can you be more specific? Do you need to read 3 analog signals with ADC? If not, any pin can be left unconfigured so they are not digital inputs.
• Shrie Sharma: @Justme See I have read the next column which says additional functions and some IO pins say that they are also ADCs but in which direction?
• Justme: Only if the pin has ADC functionality as alternate function then it can be read by ADC.
• Shrie Sharma: @Justme So how do I know which are digital and which are analog?
• Ilya: Don't forget STM32 are 3.3V devices, you may want to scale down analog/digital inputs from 5V down to 3.3V (some digital input pins can be 5V-tolerant, but only if it's explicitly stated in the datasheet for every pin in question)

Answer 1

All the analog pins are in the ADDITIONAL FUNCTIONS listed on pages 36 and following. For example from page 36 of the datasheet at:

STM32 datasheet

you have:

Additional Pin Functions

• Justme: No. Only certain pins can be read by the ADC, not all. Usually all pins can be digital outputs or inputs.
• jwh20: Find the analog pins you are interested in by reading through the "Additional Functions" column in the table. They default to the function in the "Pin name" column. To get additional functions you need to program them that way.
• jwh20: The STM32 is a bit more complicated than the Arduino. You need to study the datasheet and understand how it works.
• brhans: When it lists an 'Additional function' as ADCxINy it means that, in addition to being able to read or write this pin with a digital high/low through the GPIO registers, this pin can also be routed to the ADC module to read analog signals. It does not mean that everything presented to this pin is treated as analog and converted to digital before being processed - this is only the case if you configure the ADC to read that pin.
• TimWescott: When it says "ADC_IN" it means that the pin can be set up as an ADC input, or it can be set up as a digital I/O pin. You have to route analog signals to the correct pins, and you have to set them up in software.