Add example

Author: nseidle

libraries/Examples/examples/Advanced/Differential_ADC/Differential_ADC.ino

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+/*
+  Using the differential ADC
+  By: Nathan Seidle
+  SparkFun Electronics
+  Date: July 17th, 2020
+  License: This code is public domain. Based on deepsleep.c from Ambiq SDK v2.2.0.
+
+  There are two differential ADC ports on the Artemis. These are located
+  on pads 12/13 (DIFF0N/DIFF0P) and 14/15 (DIFF1P/DIFF10).
+
+  A differential ADC port measures -1.0V to 1.0V with
+  0 = -1.0V, 8192 = 0V, and 16383 = 1.0V when the ADC is in 14-bit mode.
+
+  SparkFun labored with love to create this code. Feel like supporting open source hardware?
+  Buy a board from SparkFun! https://www.sparkfun.com/products/15376
+*/
+
+#define ANALOG_RESOLUTION 14 //Artemis has 14 bit ADC but can range from 8 to 14 bit
+
+int maxADCValue = pow(2, ANALOG_RESOLUTION);
+
+void setup()
+{
+    Serial.begin(115200);
+    Serial.println("Differential analog conversion example");
+
+    pinMode(LED_BUILTIN, OUTPUT);
+
+    analogReadResolution(ANALOG_RESOLUTION); //Default is 10 bit. Increase to 14 bit.
+}
+
+void loop()
+{
+    int myAnalog0 = analogRead(ADIFF0); //Pads 12/13. Pins 9/10 on RedBoard Artemis.
+    //int myAnalog0 = analogRead(ADIFF1); //Pads 14/15
+    float myVoltage0 = mapfloat(myAnalog0, 0, maxADCValue, -1.0, 1.0);
+    Serial.print("Diff0 voltage: ");
+    Serial.print(myVoltage0, 3);
+    Serial.println();
+
+    digitalWrite(LED_BUILTIN, HIGH);
+    delay(25);
+    digitalWrite(LED_BUILTIN, LOW);
+    delay(25);
+}
+
+float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)
+{
+    if (x > in_max)
+        x = in_max;
+
+    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+}