chore: add ADC internal channels example

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

examples/Peripherals/ADC/Internal_channels/Internal_channels.ino

@@ -0,0 +1,98 @@
+/*
+  Internal_channels
+  This example shows how to read then convert to proper Unit the 3 internal channels + A0.
+
+  analogRead() can now be used to read some internal channels with the following definitions:
+    ATEMP: internal temperature sensor
+    AVREF: VrefInt, internal voltage reference
+    AVBAT: Vbat voltage
+
+  A minimum ADC sampling time is required when reading internal channels
+  so default is set it to max possible value.
+  It can be defined more precisely by defining:
+    ADC_SAMPLINGTIME_INTERNAL to the desired ADC sample time.
+
+  ADC_SAMPLINGTIME and ADC_CLOCK_DIV could also be redefined by the variant or using build_opt.h.
+
+  This example is provided "as it" and can require some update mainly for datasheet values.
+*/
+
+#include "stm32yyxx_ll_adc.h"
+
+/* Values available in datasheet */
+#define CALX_TEMP 25
+#if defined(STM32F1xx)
+#define V25       1430
+#define AVG_SLOPE 4300
+#define VREFINT   1200
+#elif defined(STM32F2xx) || defined(STM32F4xx)
+#define V25       760
+#define AVG_SLOPE 2500
+#define VREFINT   1210
+#endif
+
+/* Analog read resolution */
+#define LL_ADC_RESOLUTION LL_ADC_RESOLUTION_12B
+#define ADC_RANGE 4096
+
+// the setup routine runs once when you press reset:
+void setup() {
+  // initialize serial communication at 9600 bits per second:
+  Serial.begin(9600);
+  while (!Serial);
+  analogReadResolution(12);
+}
+
+static int32_t readVref()
+{
+#ifdef __LL_ADC_CALC_VREFANALOG_VOLTAGE
+#ifdef STM32U5xx
+  return (__LL_ADC_CALC_VREFANALOG_VOLTAGE(ADC1, analogRead(AVREF), LL_ADC_RESOLUTION));
+#else
+  return (__LL_ADC_CALC_VREFANALOG_VOLTAGE(analogRead(AVREF), LL_ADC_RESOLUTION));
+#endif
+#else
+  return (VREFINT * ADC_RANGE / analogRead(AVREF)); // ADC sample to mV
+#endif
+}
+
+#ifdef ATEMP
+static int32_t readTempSensor(int32_t VRef)
+{
+#ifdef __LL_ADC_CALC_TEMPERATURE
+#ifdef STM32U5xx
+  return (__LL_ADC_CALC_TEMPERATURE(ADC1, VRef, analogRead(ATEMP), LL_ADC_RESOLUTION));
+#else
+  return (__LL_ADC_CALC_TEMPERATURE(VRef, analogRead(ATEMP), LL_ADC_RESOLUTION));
+#endif
+#elif defined(__LL_ADC_CALC_TEMPERATURE_TYP_PARAMS)
+  return (__LL_ADC_CALC_TEMPERATURE_TYP_PARAMS(AVG_SLOPE, V25, CALX_TEMP, VRef, analogRead(ATEMP), LL_ADC_RESOLUTION));
+#else
+  return 0;
+#endif
+}
+#endif
+
+static int32_t readVoltage(int32_t VRef, uint32_t pin)
+{
+#ifdef STM32U5xx
+  return (__LL_ADC_CALC_DATA_TO_VOLTAGE(ADC1, VRef, analogRead(pin), LL_ADC_RESOLUTION));
+#else
+  return (__LL_ADC_CALC_DATA_TO_VOLTAGE(VRef, analogRead(pin), LL_ADC_RESOLUTION));
+#endif
+}
+
+// The loop routine runs over and over again forever:
+void loop() {
+  // Print out the value read
+  int32_t VRef = readVref();
+  Serial.printf("VRef(mv)= %i", VRef);
+#ifdef ATEMP
+  Serial.printf("\tTemp(°C)= %i", readTempSensor(VRef));
+#endif
+#ifdef AVBAT
+  Serial.printf("\tVbat(mv)= %i", readVoltage(VRef, AVBAT));
+#endif
+  Serial.printf("\tA0(mv)= %i\n", readVoltage(VRef, A0));
+  delay(200);
+}