/* Sample program to display 2014 on seven-segment display of Wytec EduBase board 
 * The four-digit seven-segment display is connected to two 8-bit shift registers 
 * on SPI in series. The shift register closer to the MCU is used to select active
 * digit. The shift register away from the MCU is used to select the segments of 
 * the display.
 * The seven-segment display has common cathode. The segment select is high active
 * and the digit select is low active.
 */

#include <SPI.h>

// use PC7 as the slave select for seven segment display
/* Tiva TM4C123 */ //const int slaveSelectPin = PC_7;
const int slaveSelect = 34;

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

void loop() {
    sevenSegWrite(0x5B, ~(1 << 3));  // write 2 to digit 3
    delay(4);
    sevenSegWrite(0x3F, ~(1 << 2));  // write 0 to digit 2
    delay(4);
    sevenSegWrite(0x06, ~(1 << 1));  // write 1 to digit 1
    delay(4);
    sevenSegWrite(0x66, ~(1 << 0));  // write 4 to digit 0
    delay(4);
}

// write digit pattern and digit select to the shift registers
void sevenSegWrite(int pattern, int digit)
{
    // assert SS low to the shift register of seven-segment LED
    digitalWrite(slaveSelect, LOW);
    // send the digit pattern and digit select via SPI
    SPI.transfer(pattern);
    SPI.transfer(digit);
    // deassert SS
    digitalWrite(slaveSelect, HIGH); 
}