The Start bit informs the receiver that a word of data is about to be sent, this is to tell the receiver to synchronise its clock with the transmitter’s clock. If the sender and receiver are not configured the same (these timing parameters), communication will not be done effectively. In asynchronous transmission, the sender sends a Start bit, 5 to 8 data bits (Least Significant Bit first), an optional Parity bit, and then 1, 1.5 or 2 Stop bits. In this case, the sender and receiver must agree on timing parameters (Baud Rate) prior transmission and special bits are added to each word to synchronize the sending and receiving units.
Serial transmission of digital information (bits) through a single wire or other medium is much more cost effective than parallel transmission which requires multiple wires. Communication can be “full duplex” (both send and receive at the same time) or “half duplex” (devices take turns transmitting and receiving).Īsynchronous transmission allows data to be transmitted without the sender having to send a clock signal to the receiver. The device changes incoming parallel information (within the microcontroller/PC) to serial data which can be sent on a communication line.Īt the destination, a second UART re-assembles the bits into complete bytes. Most PIC microcontrollers have an internal UART at a specific pins of the microcontrollers but this feature can also be implemented with any pin with Software in most of the compilers like MPLAB XC8. UART is also a common integrated feature in most microcontrollers today which is useful for communicating serial data (text, numbers, etc.) to your PC.
The Universal Asynchronous Receiver/Transmitter (UART) controller is the key component of the serial communications between a device and a PC or between devices.
Figure 1: PIC18F26K20 Connected to PC via MAX232Ī serial port interface can be used for serial communication of data (send and receive) where data is sent or received one bit at a time between a personal computer (PC) and various devices supporting this type of protocol like PIC microcontrollers, GPS, GSM modem etc. While other interfaces like Ethernet, FireWire, and USB all send data as a serial stream, the term “serial port” usually identifies hardware more or less compliant to the RS-232 standard, intended to interface with a modem or with a similar communication device. RS232 Serial communication is still widely used in industrial application and with many electronic devices like modems but it is being replaced by the USB in portable devices.