ec_uart.com2

parameters {
    wire tx;
    integer baud;
    integer bit_period = 1000000/baud;
    integer stop_bits = 1;
}

variables {
    byte data;
    bit resend;
    bit parity;
}

states {
    IDLE: (tx){
        tx --> 1;
    }

    START: (bit_period us){
        tx --> 0;   
    }

    for $s from 0 to 1 {
        for $i from 0 to 3 {
            BIT_$s_$i: (bit_period us){
                tx ==> data[4 * $s + $i];
            }
        }
        (bit_period us) {
            parity = data[4 * $s] ^ data[4 * $s + 1] ^ data[4 * $s + 2] ^ data[4 * $s + 3]; 
            tx ==> parity;
        }
        (bit_period us) {
            resend = parity != (data[4 * $s] ^ data[4 * $s + 1] ^ data[4 * $s + 2] ^ data[4 * $s + 3]);
            resend <== tx; 
        }[resend => BIT_$s_0]
    }

    STOP: (bit_period * stop_bits us){
        tx --> 1;
    }[=> IDLE]

}

shared {
    fn com2_ec_uart_setup() {
        ...IDLE;
    }
}

left {
    fn com2_ec_uart_send(output byte x) {
        data = x;
        START...IDLE;
    }
}

right {
    fn com2_ec_uart_recv(input byte x) {
        IDLE...IDLE;
        x = data;
    }
}