void printout(uint16_t col) {

    uint16_t offset = col * 288;
    uint16_t i;

    SCLK = 0;
    XLAT = 0;

    for (i = 0; i < 288; i ++) {
        SOUT_PORT = buf[offset++] & 0x3F;
        SCLK = 1;
        SCLK = 0;
    }

    /* On the rising edge of XLAT, grayscale data is transferred
     * from the shift register to the latch */
    BLANK = 1;
    XLAT = 1;
    XLAT = 0;
    /* Wait another clock cycle, then turn on the LEDs ! */
    BLANK = 0;
}