#Types of serial communication code#

The second approach is invariably used in wireless systems to avoid dedicating a separate frequency channel to the clock signal. The SPI bus which IвЂ™ll talk about next time is frequently used in this situation. For example, when linking a peripheral device to a microcontroller on the same PCB. The first method is used over short distances where there is no problem providing an extra wire.

The receiver вЂrecoversвЂ™ the clock from the data signal itself.

The transmitter clock is supplied to the receiver via another wire.

One feature of all types of digital communication system is that the clock signal which puts the data on the line, in the serial case one bit at a time, is precisely synchronised with the receiverвЂ™s clock taking it off. The signal line is held in the вЂoneвЂ™ state when nothing is being transmitted. For signalling purposes each character is preceded by a Start bit - always a zero, and ends with a Stop bit (always a one).

#Types of serial communication code#

To make life easier, each character is represented by a fixed-length 5-bit binary code (unlike Morse) and the distinction between вЂzerosвЂ™ and вЂonesвЂ™ based on voltage or current level, not pulse length ( Fig.1). The electromechanical Asynchronous Receiver Transmitter was born.

All this had to be achieved with the only technology available at the time: mechanical mechanisms driven by electric motors and solenoids. A way had to be found for converting a key press to a coded stream of electrical pulses, which could then be decoded and converted to a character printed on paper at the receiving end. What was needed was a means of replacing the Morse keys with office typewriter keyboards. Though when combined with long-range HF radio, itвЂ™s great for sending three-character messages like вЂњSOSвЂќ from ships in distress. Sending and reading messages in Morse code was never going to catch on as a means of mass communication because itвЂ™s too slow and requires a trained operator at each end. I wonвЂ™t cover the very similar вЂ Ticker-tapeвЂ™ systems designed for stock market price communication as these are now well and truly obsolete. Alternatively, the ticks and tocks of the solenoid could be interpreted directly by a trained Morse code telegraphist.

At the receiving end, a solenoid-driven ink stylus reproduced these вЂmarks and spacesвЂ™ on paper tape fed from a roll by a clockwork motor. A human operator sent text characters encoded in groups of short and long current pulses (dots and dashes) by tapping a sprung-loaded switch known as a Morse key. In the days before voice could be converted to an (analogue) electrical signal and conveyed over long distances by wire, there was digital telegraphy. How do they work and which to choose? Early Telegraphy

Microcontrollers usually support one or more of three basic types: UART, SPI and I 2C. Most modern peripheral device chips, such as sensors and motor drivers, communicate with a controller via a serial data bus.