component serial_dac        "This component converts the lower 12 bits of an unsigned 32 bit word into serial output intended for a Linear Technology LTC1257 unipolar DAC. (2007/12/29 kwallace@wallacecompany.com)";

pin in unsigned data_in     "This is the value to convert to serial binary.";

pin out bit dac_clock       "This commands (on the rising edge) the DAC to clock the n'th bit into the DAC's shift register.";
pin out bit dac_bit         "This is the value of the n'th bit to output to the DAC's shift regester.";
pin out bit dac_load        "This commands (on the falling edge) the DAC to copy the contents of the shift register to the DAC register, resulting in the ouput of the new voltage.";

variable unsigned cycle;    //This holds the value of which bit is being sent. MSB bit 11 first to LSB bit 0 last
variable unsigned phase;    //This holds the value of which phase of the n'th bit being sent. There are four phases;get bit, shift bit, wait (also, test for last bit for load*),reset clock (also, test for last bit for cycle reset).";
variable unsigned data_adj; //This holds the adjusted data_in value. data_in will wrap (i.e. 5000 wraps to 904) if it's not clamped to 4095.

function _ nofp;
function in_adj nofp;
license "GPL";

;;

FUNCTION(in_adj) {
    if (data_in < 0) { data_adj=0; }
    if (data_in > 4095) { data_adj=4095; } else { data_adj=data_in; }
}

FUNCTION(_) {
    switch (phase) {
    case 0:
        dac_bit=0x1 & (data_adj >> cycle);
        dac_clock=0;
        dac_load=1;
        phase=1;
        break;
    case 1:
        dac_clock=1;
        phase=2;
        break;
    case 2:
        if (cycle<=0) { dac_load=0; }
        phase=3;
        break;
    case 3:
        dac_clock=0;
        if (cycle<=0) { cycle=11; } else { cycle--; }
        phase=0;
        break;
    }
}