/* Program to display a counter counting from 0 to 3 on seven-segment display of 
 * Wytec EduPad board with Tiva TM4C123/MSP432.
 * The seven-segment display is connected to an 8-bit shift registers on SPI. 
 * The shift register is used to select the segments of the display.
 * The seven-segment display has common cathode. The segment select is high active.
 * 
 * Energia 1.6.10E18
 */

#include <SPI.h>

const int slaveSelect = 34;

void setup() {
    // set the slaveSelectPin as an output:
    pinMode (slaveSelect, OUTPUT);
    // initialize SPI:
    SPI.begin();
}

void loop() {
    const static unsigned char digitPattern[] = {0x3F, 0x06, 0x5B, 0x4F};
    static int i;

    // assert SS low to the shift register of seven-segment LED
    digitalWrite(slaveSelect, LOW);
    // send the digit pattern SPI
    SPI.transfer(~digitPattern[i++ % 3]);
    // deassert SS
    digitalWrite(slaveSelect, HIGH); 
    delay(1000);
}