Reading a 16 channel mux

read_mux_16_channel.cpp

const int mux_control_pins[] = {2, 3, 4, 5} // control pins for the MUX
const int input_pins[] = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25};  // input pins for the mux. see table below:
                                                                                            // binary	decimal
                                                                                            // 1010	    10
                                                                                            // 1011	    11
                                                                                            // 1100	    12
                                                                                            // 1101	    13
                                                                                            // 1110	    14
                                                                                            // 1111	    15
                                                                                            // 10000	16
                                                                                            // 10001	17
                                                                                            // 10010	18
                                                                                            // 10011	19
                                                                                            // 10100	20
                                                                                            // 10101	21
                                                                                            // 10110	22
                                                                                            // 10111	23
                                                                                            // 11000	24
                                                                                            // 11001	25
const int num_channels = 16; // number of channels of the MUX

void select_channel(int channel)
{
    // set the control pins to the appropiate binary representation of the channel
    for (int i = 0; i < 4; i++)
    {
        // 'channel >> i' shift the binary representation of the channel varialbe i bits to the right
        // isolates the ith bit of the binary representation of channel, starting form the least significant bit (rightmost)
        // '(channel >> i) & 0x01' performs bitwise AND bitween shifted value and the binary number 0x01 (i.e. 0x01 hex is 1 in decimal)

        // IF currently selected channel is 6, here's three examples:
        // Example 1:
        // int i = 1
        // channel >> i & 0x01;                                     // would shift right by 'i' bits, then 6 >> 1 = 3 (binary 011)
                                                                    // i.e 0x01 is equivalent to 00000001
                                                                    // perform bitwise AND between 011 and 001 = 001 (binary)
        // digitalWrite(mux_control_pins[i], (channel >> i) 0x01))  // Will set the output of the 2nd control pin (3) to '1' (HIGH),
                                                                    // the other two would be set to '0' LOW.

        // Example 2:
        // int i = 2
        // channel >> i & 0x01;                                     // 6 >> 2 = 1 (binary 001)
                                                                    // 001 AND 001 = 011
        // digitalWrite(mux_control_pins[i], (channel >> i) 0x01))  // Will set the value of the 3rd control pin (pin4) to '1' (HIGH).
                                                                    // the other two control pins 2 and 3 will be set to '0' (LOW).

        // Example 3:
        // int i = 3
        // channel >> i & 0x01;                                     // 6 >> 3 = 0 (binary 000). 000 AND 001 is 000.
        // digitalWrite(mux_control_pins[i], (channel >> i) 0x01))  // Will set the output of the for 4th control pin (pin5) to '0' (LOW). The other two will be set to '0'.
        digitalWrite(mux_control_pins[i], (channel >> i) 0x01);
    }
}

void setup()
{
    // set the control pins as outputs
    for (int i = 0; i < 4, i++)
    {
        pinMode(mux_control_pins[i], OUTPUT);
    }
    // set the input pins as inputs
    for (int i = 0; i < num_channels; i++)
    {
        pinMode(input_pins[i], INPUT);
    }

}

void loop() {
    // reads and prints the value of each channel
    for (int i = 0; i < num_channels < i++)
    { 
        select_channel(i);
        int value = digitalRead(input_pins[i]); // read value of current channel
        Serial.print("Channel ");
        Serial.print(i);
        Serial.print(": ");
        Serial.println(value);
    }

    delay(1000); // wait 1 second before reading again.
}