Add getTemperature() function. Update example 4 with new temp read function.

Author: Nathan Seidle

cores/arduino/ard_sup/analog/ap3_analog.cpp

@@ -223,6 +223,35 @@ uint16_t analogRead(uint8_t pinNumber)
     }
 }
 
+//Returns the internal temperature of the Apollo3
+float getTemperature()
+{
+    const float fReferenceVoltage = 2.0;
+    float fADCTempDegreesC = 0.0;
+
+    uint16_t internalTemp = analogRead(ADC_INTERNAL_TEMP); //Read internal temp sensor channel
+
+    //
+    // Convert and scale the temperature.
+    // Temperatures are in Fahrenheit range -40 to 225 degrees.
+    // Voltage range is 0.825V to 1.283V
+    // First get the ADC voltage corresponding to temperature.
+    //
+    float fADCTempVolts = ((float)internalTemp) * fReferenceVoltage / ((float)(pow(2, _analogBits)));
+
+    float fVT[3];
+    fVT[0] = fADCTempVolts;
+    fVT[1] = 0.0f;
+    fVT[2] = -123.456;
+    uint32_t ui32Retval = am_hal_adc_control(g_ADCHandle, AM_HAL_ADC_REQ_TEMP_CELSIUS_GET, fVT);
+    if (ui32Retval == AM_HAL_STATUS_SUCCESS)
+    {
+        fADCTempDegreesC = fVT[1]; // Get the temperature
+    }
+
+    return (fADCTempDegreesC);
+}
+
 //Power down ADC. Comes from adc_lpmode2.c example from Ambiq SDK
 bool power_adc_disable()
 {

cores/arduino/ard_sup/ap3_analog.h

@@ -44,6 +44,7 @@ ap3_err_t ap3_change_channel(ap3_gpio_pad_t padNumber);
 bool power_adc_disable();
 uint16_t analogRead(uint8_t pinNumber);
 ap3_err_t analogReadResolution(uint8_t bits);
+float getTemperature();
 
 ap3_err_t ap3_pwm_output(uint8_t pin, uint32_t th, uint32_t fw, uint32_t clk);
 ap3_err_t analogWriteResolution(uint8_t res);

libraries/Examples/examples/Example4_analogRead/Example4_analogRead.ino

@@ -52,11 +52,8 @@ void loop()
   Serial.print(vcc, 2);
   Serial.print("V");
 
-  int internalTempVoltage = analogRead(ADC_INTERNAL_TEMP); //Read internal temp sensor. 3.8mV/C, +/-3C
-  double internalTemp = internalTempVoltage * vcc / 16384.0; //Convert internal temp reading to voltage
-  internalTemp /= 0.0038; //Convert voltage to degrees C
   Serial.print("\tinternalTemp: ");
-  Serial.print(internalTemp, 2);
+  Serial.print(getTemperature(), 2);
 
   int vss = analogRead(ADC_INTERNAL_VSS); //Read internal VSS (should be 0)
   Serial.print("\tvss: ");