#include <stdio.h>
#include <fcntl.h>
#include <font.h>

#define GPIO_DOUT (1<<1)
#define GPIO_CLK  (1<<2)
#define GPIO_CS   (1<<3)
#define GPIO_DC   (1<<7)

int gpio_out;

unsigned char lcdram[6][84] = {0};
unsigned char *lcdram_ptr = &lcdram[0][0];

void setpins(int dout, int clk, int cs, int dc) {
    unsigned int reg;

    read(gpio_out, &reg, sizeof(reg));
    
    if (dout)
        reg |= GPIO_DOUT;
    else
        reg &= ~GPIO_DOUT;
    
    if (clk)
        reg |= GPIO_CLK;
    else
        reg &= ~GPIO_CLK;
    
    if (cs)
        reg |= GPIO_CS;
    else
        reg &= ~GPIO_CS;
    
    if (dc)
        reg |= GPIO_DC;
    else
        reg &= ~GPIO_DC;
    
    write(gpio_out, &reg, sizeof(reg));
    usleep(1000);
}

void spi_writebyte(unsigned char byte, int dc) {
    int i, bit;
    
    setpins(0, 0, 0, dc);
    
    for (i = 7; i >= 0; i--) {
        bit = byte & (1 << i);
        
//         setpins(bit, 0, 0, dc);
        setpins(bit, 1, 0, dc);
        setpins(bit, 0, 0, dc);
    }
}

void cursorxy(int x, int y) {
    spi_writebyte(0x40 | (y & 0x07), 0);
    spi_writebyte(0x80 | (x & 0x7f), 0);
}

void updateram() {
    cursorxy(0, 0);
    
    unsigned char *p;
    
    for (p = lcdram_ptr; p < lcdram_ptr + 504; p++) {
        spi_writebyte(*p, 1);
    }
}

void init() {
    setpins(0, 0, 0, 0);
    usleep(10000);

    setpins(0, 0, 1, 0);

    spi_writebyte(0x21, 0); // Extended instruction set
    spi_writebyte(0xC2, 0); // LCD contrast voltage
    spi_writebyte(0x13, 0); // LCD bias
    spi_writebyte(0x20, 0); // Normal instruction set
    spi_writebyte(0x0C, 0); // Display normal
    updateram();
    
    setpins(0, 0, 0, 0);
}

void speedtest() {
    unsigned char *p = lcdram_ptr;
    int i;
    for (i = 0; i < 504; i++) {
        p++;
        
        if (i % 5 == 4)
            *p = 0;
        else
            *p = font_data[i / 5 + 32][i % 5];
    }
    
    int x, y, carry, oldcarry;
    
    while (1) {
        for (x = 0; x < 84; x++) {
            carry = (lcdram[5][x] & 0x80) >> 7;
            for (y = 0; y < 6; y++) {
                oldcarry = carry;
                carry = (lcdram[y][x] & 0x80) >> 7;
                lcdram[y][x] = (lcdram[y][x] << 1) | oldcarry;
            }
        }
        
        updateram();
        usleep(20000);
    }
}

int main() {
    unsigned int reg;

    int gpioouten=open("/dev/gpio/outen",O_RDWR);
    read(gpioouten, &reg, sizeof(reg));
    reg |= GPIO_DOUT | GPIO_CLK | GPIO_CS | GPIO_DC;
    write(gpioouten, &reg, sizeof(reg));

    gpio_out = open("/dev/gpio/out", O_RDWR);
    
    init();
    
    speedtest();
}