#include <stdio.h>
#include <fcntl.h>
#include <font.h>
#include <sys/ioctl.h>

#define SPI_COMMAND 0x600

int spidev;

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

void spi_command(unsigned char command) {
    ioctl(spidev, SPI_COMMAND, &command);
}

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

void updateram() {
    cursorxy(0, 0);
    
    write(spidev, lcdram_ptr, 504);
}

void init() {
    spi_command(0x21); // Extended instruction set
    spi_command(0x80 | 70); // LCD contrast voltage
    spi_command(0x13); // LCD bias
    spi_command(0x20); // Normal instruction set
    spi_command(0x0C); // Display normal
    updateram();
}

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, count = 0, sleep;
    
    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();
        
        sleep = abs(250000 - (count % 500000)) / 100;
        count += sleep;
        printf("%d\n", sleep);
        usleep(sleep);
    }
}

int main() {
    spidev = open("/dev/spi", O_RDWR);
    
    init();
    
    speedtest();
}