/* P12_1.c: PCD8544 (Nokia5110) GLCD via SPI with SAMD21
 *
 * Letters A,B,C are written on the display.
 *
 * Interface uses SERCOM1 of SAMD21 Xplained Pro board.
 *
 * PA16  PAD0  MOSI
 * PA17  PAD1  SCK
 * PA18  SS (hardware slave select)
 * PA08  register select (DC)
 * PA09  reset
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a.
 */

#include "samd21.h"

#define RESET 0x200      /* PA09 reset */
#define DC    0x100      /* PA08 register select */

/* define the pixel size of display */
#define GLCD_WIDTH  84
#define GLCD_HEIGHT 48

void GLCD_setCursor(unsigned char x, unsigned char y);
void GLCD_clear(void);
void GLCD_init(void);
void GLCD_data_write(unsigned char data);
void GLCD_command_write(unsigned char data);
void GLCD_putchar(int c);
void SPI_init(void);
void SPI_write(unsigned char data);

unsigned char* ARRAY_PORT_PINCFG0 = (unsigned char*)&REG_PORT_PINCFG0;
unsigned char* ARRAY_PORT_PMUX0 = (unsigned char*)&REG_PORT_PMUX0;

/* sample font table */
const char font_table[][6] = {
    {0x7e, 0x11, 0x11, 0x11, 0x7e, 0},  /* A */
    {0x7f, 0x49, 0x49, 0x49, 0x36, 0},  /* B */
    {0x3e, 0x41, 0x41, 0x41, 0x22, 0}   /* C */
};

int main(void) {
    GLCD_init();        /* initialize the GLCD controller */
    GLCD_clear();       /* clear display and home the cursor */

    GLCD_putchar(0);    /* display letter A */
    GLCD_putchar(1);    /* display letter B */
    GLCD_putchar(2);    /* display letter C */

    while(1) { }
}

void GLCD_putchar(int c) {
    int i;
    for (i = 0; i < 6; i++)
        GLCD_data_write(font_table[c][i]);
}

void GLCD_setCursor(unsigned char x, unsigned char y) {
    GLCD_command_write(0x80 | x);  /* column */
    GLCD_command_write(0x40 | y);  /* bank (8 pixel rows per bank) */
}

/* clears the GLCD by writing zeros to the entire screen */
void GLCD_clear(void) {
    int32_t index;
    for (index = 0 ; index < (GLCD_WIDTH * GLCD_HEIGHT / 8) ; index++)
        GLCD_data_write(0x00);

    GLCD_setCursor(0, 0); /* return to the home position */
}

/* send the initialization commands to PCD8544 GLCD controller */
void GLCD_init(void) {
    SPI_init();

    /* hardware reset of GLCD controller */
    REG_PORT_OUTSET0 = RESET;       /* deassert reset */

    GLCD_command_write(0x21);       /* set extended command mode */
    GLCD_command_write(0xB8);       /* set LCD Vop for contrast */
    GLCD_command_write(0x04);       /* set temp coefficient */
    GLCD_command_write(0x14);       /* set LCD bias mode 1:48 */
    GLCD_command_write(0x20);       /* set normal command mode */
    GLCD_command_write(0x0C);       /* set display normal mode */
}

/* write to GLCD controller data register */
void GLCD_data_write(unsigned char data) {
    REG_PORT_OUTSET0 = DC;          /* select data register */
    SPI_write(data);                /* send data via SPI */
}

/* write to GLCD controller command register */
void GLCD_command_write(unsigned char data) {
    REG_PORT_OUTCLR0 = DC;          /* select command register */
    SPI_write(data);                /* send data via SPI */
}

void SPI_init(void) {
    REG_PM_APBCMASK |= 0x00000008;          /* SERCOM1 bus clock */
    REG_GCLK_CLKCTRL = 0x4015;              /* SERCOM1 core clock */

    ARRAY_PORT_PINCFG0[16] |= 1;    /* allow pmux to set PA16 pin configuration */
    ARRAY_PORT_PINCFG0[17] |= 1;    /* allow pmux to set PA17 pin configuration */
    ARRAY_PORT_PINCFG0[18] |= 1;    /* allow pmux to set PA18 pin configuration */
    ARRAY_PORT_PINCFG0[19] |= 1;    /* allow pmux to set PA19 pin configuration */
    ARRAY_PORT_PMUX0[8] = 0x22;     /* PA16 = MOSI, PA17 = SCK */
    ARRAY_PORT_PMUX0[9] = 0x22;     /* PA18 = SS,   PA19 = MISO */

    REG_SERCOM1_SPI_CTRLA = 1;              /* reset SERCOM1 */
    while (REG_SERCOM1_SPI_CTRLA & 1) {}    /* wait for reset to complete */
    REG_SERCOM1_SPI_CTRLA = 0x0030000C;     /* MISO-3, MOSI-0, SCK-1, SS-2, SPI master */
    REG_SERCOM1_SPI_CTRLB = 0x00002000;     /* Master SS, 8-bit */
    REG_SERCOM1_SPI_BAUD = 0;               /* SPI clock is 1MHz/2 = 500kHz */
    REG_SERCOM1_SPI_CTRLA |= 2;             /* enable SERCOM1 */

    REG_PORT_DIRSET0 = RESET | DC;  /* PA08, PA09 set as output */
    REG_PORT_OUTCLR0 = RESET;       /* assert reset */
}

void SPI_write(unsigned char data) {
    while(!(REG_SERCOM1_SPI_INTFLAG & 1)) {}    /* wait until Tx ready */
    REG_SERCOM1_SPI_DATA = data;                /* send data byte */
}