2014-05-11 04:08 AM
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 #discovery2014-05-11 06:19 AM
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. -Bill2014-05-11 08:54 AM
2014-05-11 09:20 AM
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.