Hey I have created a single line high speed serial communications interface. This post is for those that want more information.

The system is very simple, to keep it compact. First a Start bit is transmitted along the line followed by 8 data bits. The HIGH state of the transmission line indicates a 1 and the LOW state indicates a 0. There are two options for the serial transmission. Single line or double line. Double line is more similar to an SPI interface because it is full duplex. Single line mode is half duplex. With single line mode the controller will sit in recieve mode until the write pin is brought high. At that point it will jump into transmit mode for the duration of transmission and then return to recieve mode.

Pseudocode for using these devices:

void transmit(uint8_t x) {
write(regSend, x);
portTriggerPin(write);
}

uint8_t recieve (uint8_t * x) {
*x = portTriggerPin(read);
if (portTestPin(recieve)) {
return 0;
} else {
return 1;
}
}


Example Master:

int main() {
uint8_t recieved;
while (1) {
transmit(0x4a);
while (recieve(&recieved));
printf("Recieved: %d", recieved);
}
return 0;
}


Example Slave:

int main() {
uint8_t recieved;
while (1) {
while(recieve(&recieved));
if (recieved == 0x4a) {
transmit(0x10);
} else {
transmit(0x01);
}
}
}


Limitations: 

1. No speed control. 1 speed of Very Fast only.
2. Cannot be rotated. The device must always remain upright.
3. No collision detection. If the transmitter sends two bytes before the reciever has read the first one the bytes will be silently OR'd together.