Introduce a new demo sketch to visulize the

attenuation and offset constraints of the input
cv.

analog_input.h

@@ -4,25 +4,29 @@
  * @brief Class for interacting with analog inputs.
  * @version 0.1
  * @date 2025-05-23
- * 
+ *
  * @copyright Copyright (c) 2025
- * 
+ *
  */
 #ifndef ANALOG_INPUT_H
 #define ANALOG_INPUT_H
 
 const int MAX_INPUT = (1 << 10) - 1;  // Max 10 bit analog read resolution.
 
+// estimated default calibration value
+const int CALIBRATED_LOW = -566;
+const int CALIBRATED_HIGH = 512;
+
 class AnalogInput {
    public:
     AnalogInput() {}
     ~AnalogInput() {}
 
     /**
-    * Initializes a analog input object.
-    * 
-    * @param pin gpio pin for the analog input.
-    */
+     * Initializes a analog input object.
+     *
+     * @param pin gpio pin for the analog input.
+     */
     void Init(uint8_t pin) {
         pinMode(pin, INPUT);
         pin_ = pin;
@@ -30,33 +34,43 @@ class AnalogInput {
 
     /**
      * Read the value of the analog input and set instance state.
-     * 
+     *
      */
     void Process() {
         old_read_ = read_;
         int raw = analogRead(pin_);
-        read_ = map(raw, offset_, MAX_INPUT, low_, high_);
+        read_ = map(raw, 0, MAX_INPUT, low_, high_);
+        read_ = constrain(read_ - offset_, -512, 512);
+        if (inverted_) read_ = -read_;
     }
 
     // Set calibration values.
 
     void AdjustCalibrationLow(int amount) { low_ += amount; }
-    void AdjustCalibrationOffset(int amount) { offset_ -= amount; }
+
     void AdjustCalibrationHigh(int amount) { high_ += amount; }
 
+    void SetOffset(float percent) { offset_ = -(percent)*512; }
+
+    void SetAttenuation(float percent) {
+        low_ = abs(percent) * CALIBRATED_LOW;
+        high_ = abs(percent) * CALIBRATED_HIGH;
+        inverted_ = percent < 0;
+    }
+
     /**
      * Get the current value of the analog input within a range of +/-512.
-     * 
+     *
      * @return read value within a range of +/-512.
-     * 
+     *
      */
     inline int16_t Read() { return read_; }
 
     /**
      * Return the analog read value as voltage.
-     * 
+     *
      * @return A float representing the voltage (-5.0 to +5.0).
-     * 
+     *
      */
     inline float Voltage() { return ((read_ / 512.0) * 5.0); }
 
@@ -66,8 +80,9 @@ class AnalogInput {
     uint16_t old_read_;
     // calibration values.
     int offset_ = 0;
-    int low_ = -512;
-    int high_ = 512;
+    int low_ = CALIBRATED_LOW;
+    int high_ = CALIBRATED_HIGH;
+    bool inverted_ = false;
 };
 
 #endif