/*
 * Display number 2014 on the seven-segment LED for FRDM-KL25Z
 * with Wytec EduBase.
 * The four digit seven segment LED is driven by two shift registers,
 * one to control the anodes (segments) and the other the common cathodes
 * (digit select).  The shift registers are daisy-chained to SPI0
 * of the FRDM-KL25Z.
 * Each digit is enabled for 4 ms.  With four digits, the cycle time is
 * 4 ms * 4 = 16 ms that translates to 62.5 Hz.
 */

#include "MKL25Z4.h"

void delayMs(int n);
void SPI0_init(void);
void SPI0_write(unsigned char data);

int main(void)
{
    // initialize SPI0 that connects to the shift registers
    SPI0_init();

    while(1)
    {
        SPI0_write(0x5B);       // write pattern 2 to the seven segments
        SPI0_write(~(1 << 3));  // select digit 3
        delayMs(4);

        SPI0_write(0x3F);       // write pattern 0 to the seven segments
        SPI0_write(~(1 << 2));  // select digit 2
        delayMs(4);

        SPI0_write(0x06);       // write pattern 1 to the seven segments
        SPI0_write(~(1 << 1));  // select digit 1
        delayMs(4);

        SPI0_write(0x66);       // write pattern 4 to the seven segments
        SPI0_write(~(1 << 0));  // select digit 0
        delayMs(4);
    }
}

void SPI0_init(void) {
    SIM->SCGC5 |= 0x1000;       /* enable clock to Port D */
    PORTD->PCR[1] = 0x200;      /* make PTD1 pin as SPI SCK */
    PORTD->PCR[2] = 0x200;      /* make PTD2 pin as SPI MOSI */

    SIM->SCGC4 |= 0x400000;     /* enable clock to SPI0 */
    SPI0->C1 = 0x10;            /* disable SPI and make SPI0 master */
    SPI0->BR = 0x60;            /* set Baud rate to 1 MHz */
    SPI0->C1 |= 0x40;           /* Enable SPI module */

    SIM->SCGC5 |= 0x0800;       /* enable clock to Port C */
    PORTC->PCR[9] = 0x100;      /* make PTC9 pin as GPIO */
    PTC->PDDR |= 1 << 9;        /* make PTC9 as output pin for /SS */
    PTC->PSOR = 1 << 9;         /* make PTC9 idle high */
}

void SPI0_write(unsigned char data) {
    volatile char dummy;

    PTC->PCOR = 1 << 9;             /* assert /SS */

    while(!(SPI0->S & 0x20)) { }    /* wait until tx ready */
    SPI0->D = data;                 /* send data byte */
    while(!(SPI0->S & 0x80)) { }    /* wait until tx complete */
    dummy = SPI0->D;                /* clear SPRF */

    PTC->PSOR = 1 << 9;             /* deasssert /SS */
}

// delay n milliseconds (41.94MHz CPU clock)
void delayMs(int n)
{
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 7000; j++)
            {}  /* do nothing */
}