/* Program to read the analog value of the pin connected to the photo sensor.
 * The potentiometer on the Wytec EduBase/EduPad board is connected pin 27.
 * The ADC has 12 bits for TivaC and 14 bits for MSP432 but default to 10 bits 
 * in Energia. The resolution is set to 12 bit by the statement
 * analogReadResolution(12);
 * so the value has the range of 0 - 4095. The value is sent to the Serial monitor. 
 * The upper 4 bits of the conversion result is also written to the LEDs.
 * 
 * Energia 1.6.10E18
 */
 
const int LED[] = {3, 4, 19, 38};

void setup()
{
    Serial.begin(9600);
    Serial.println("Photosensor:");

    // initialize LED for display
    for (int i = 0; i < 4; i++)
        pinMode(LED[i], OUTPUT);
    
    digitalGroupWrite(LED, 4, 0);
    analogReadResolution(12);
}

// Pin 27 is connected to a photo sensor
const int photo = 27;

void loop()
{
    int photoValue;
    
    // read the voltage fromm ADC
    photoValue = analogRead(photo);
    
    // write it to the Serial monitor
    Serial.print("  Photosensor value = ");
    Serial.println(photoValue, DEC);
    
    digitalGroupWrite(LED, 4, photoValue >> 8);  // and write it to the LEDs
    delay(100);
}

// write to a group of output pins
void digitalGroupWrite(const int* group, int length, int data)
{
    for (int i = 0; i < length; i++)
        digitalWrite(group[i], data & (1 << i) ? HIGH : LOW);
}