Stm32f4 ADC reference voltages

[furqan]

Posted on May 11, 2014 at 13:08

I just started using Stm32f4 Discovery and was working with ADC to get input values from several infra red sensors.

In the datasheet there is mention of VDDA and Vref+ but I have found no such pins on my board. I want to give a reference voltage to my microcontroller and compare my input values with it but I have no clue how to do it.

Also from reading the datasheet and some training manuals I understood that ADC can convert voltages from 0 to 3.6V but I have observed that when I was giving around 3.1 or 3.2V still the ADC showed a maximum of 4096.

It would be of great help if someone guided me how to properly interface my sensors with ADC and what to do about reference voltages.

 

#adc #stm32f4 #discovery

[Bill Lewis]

Posted on May 11, 2014 at 15:19

See Sheet 4 of the STM32F4 Discovery schematic.

It shows how the VDDA and VREF+ pins are connected.

You could provide your own source by modifying the board, removing L1, and tapping in there.

-Bill

 

[furqan]

Posted on May 11, 2014 at 17:54

Thank you for your reply but I am still see there are no ''physical'' pins labelled Vdda or Vref+. There are only three Vdd pins which i presume means Vdd = Vdda..?

[Tesla DeLorean]

Posted on May 11, 2014 at 18:20

All the supply pins are connected to 3V, this limits your analogue inputs to that as a maximal value.

You could examine the schematic and inject up to 3.6V on the VDD side of JP1/SB17 if you wanted to run the STM32F4 at a higher voltage.