The DB-25 parallel port has a total of 25 pins where only 8 pins are data pins, 8 pins are GND and 9 pins are other signals not directly related to the data transferred.Īnother drawback with parallel vs serial is that you get interference between the lines with long cables. (Image: Rainer Knäpper, Free Art License) If you for instance want to transfer 8-bit ASCII values you need eight wires for the data, a common GND, a clock wire for synchronous transmission (which we’ll talk about later) and other dedicated wires for any other signal you want to transfer. This quickly adds up to quite a lot of wires, which is less than ideal when working with microcontrollers with a limited amount of pins. However, it uses as many data wires as the bit width (sending 8-bit messages will require eight data wires). Parallel communication is very basic, easy to implement and has a fast transfer rate. The two main types of wired digital embedded communication are serial and parallel. There is a huge variety of protocols and standards to choose from, all with their advantages and disadvantages. In addition you have the more basic analog or PWM signal methods which are also used to communicate between devices, but we won’t talk about these today. This whole post encompasses only digital communication standards. A PCB we’ve designed for an earlier project that utilizes serial communication. These protocols and standards define how different parts of an embedded system communicate with each other, for instance how a sensor or an actuator communicates with a microcontroller. If you’re going to design embedded hardware you have know your way around the most common wired digital communication protocols and standards.
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