How to use and configure ADC of STM32F407G-Discovery with nanoFramework?

Question

I try to use ChibiOS presetted ADCs. Available channels following the specification:

• PC1, ADC1 IN11
• PC2 ADC1 IN12
• PA6 ADC2 IN6
• PA7 ADC2 IN7
• PB0 ADC2 IN8
• Temp Sensor ADC1
• VrefInt ADC1
• Vbatt ADC1

Presetted ADCs from ChibiOS' build source (target_system_device_adc_config.cpp):

#include <sys_dev_adc_native_target.h>
 
const NF_PAL_ADC_PORT_PIN_CHANNEL AdcPortPinConfig[] = {
 
    // ADC1
    {1, GPIOC, 1, ADC_CHANNEL_IN11},
    {1, GPIOC, 2, ADC_CHANNEL_IN12},
 
    // ADC2
    {2, GPIOA, 6, ADC_CHANNEL_IN6},
    {2, GPIOA, 7, ADC_CHANNEL_IN7},
    {2, GPIOB, 0, ADC_CHANNEL_IN8},
 
    // these are the internal sources, available only at ADC1
    {1, NULL, 0, ADC_CHANNEL_SENSOR},
    {1, NULL, 0, ADC_CHANNEL_VREFINT},
    {1, NULL, 0, ADC_CHANNEL_VBAT},
};
 
const int AdcChannelCount = ARRAYSIZE(AdcPortPinConfig);

How to use ADCs? Is there some way to configure ADC in C# code? I would appreciate any help. Thank you

I wrote this code:

using System;
using System.Diagnostics;
using System.Threading;
using System.Device.Adc;
 
namespace ADCMeasure
{
    public class Program
    {
        private static int adcValue;
 
        public static void Main()
        {
            AdcController adcController = new AdcController();
            AdcChannel pa6Channel = adcController.OpenChannel(6);
 
            while (true)
            {
                adcValue = pa6Channel.ReadValue();
                double ratio = pa6Channel.ReadRatio();
                Debug.WriteLine($"{nameof(adcValue)}: {adcValue}; {nameof(ratio)}: {ratio}; MaxValue: {adcController.MaxValue}; MinValue: {adcController.MinValue}");
                Thread.Sleep( 1000 );
            }
        }
    }
}

and have debug console output: adcValue: 1695; ratio: 0.41343101; MaxValue: 4095; MinValue: 0

It corresponds real 2.7V on PA6.

If I change the channel to 7th (adcController.OpenChannel(7)),

I have adcValue: 4; ratio: 0; MaxValue: 4095; MinValue: 0 and 0V on PA7.

If I connect PA7 (7th channel) to external 2V I have no changes in debug console but I see this 2V on PA7 by voltmeter, it would be about adcValue: 1260 and ratio: 0.30769

Answer 1

The index that you use when calling adcController.OpenChannel(6) is the index of the AdcPortPinConfig[] array. By using 7 you're reading the ADC_CHANNEL_VBAT. (mind that's 0 based)