These start and stop bits define the beginning and the end of the data packages. Therefore the receiving UART knows when to start and stop reading the bits. The specific frequency used to read the incoming bits is known as the baud rate. The baud rate is a measure used for the speed of data transfer.
The unit used for baud rate is bits per second bps. In order for the data transfer to be a success both the transmitting and receiving UART must operate at almost the same baud rate. The receiving and transmitting UART must be configured to receive the same data packages. The transmitting UART receives data from a data bus. A data bus is used to send data from another device such as a microcontroller, memory or CPU.
When the transmitting UART receives the data it processes the data by adding a start bit and a stop bit. This, in turn, creates a data package. Bit by bit the data packet is serially output at the Tx pin.
UART will then read the data packet bit by bit through its Rx pin. The receiving UART will convert the data back to its original form through removing the start bit, parity bit and stop bits. Receiver will finally transfer the data packet in parallel to the data bus.
This is how UART transmitted data is organized: It is organized into packets that have one start bit, 5 to 9 data bits. A parity bit is optional, and 2 stop bits. A total of 8 bits are sent one right after the other to transmit a byte. A bit is either a logical low or high. The time interval between two bits is called the baud rate or bit rate.
The most commonly used baud rates is bits per second. Although other baud rates are also used, but the higher the bit rate, the more chances there are of data corruption. This means that the two devices no longer need to negotiate a baud rate. The master then sends a start bit before sending the bits that contain data. With its ability to connect to multiple slaves, full-duplex communication, and lower power consumption than other synchronous protocols like I2C, SPI is used in memory devices, digital memory cards, ADC to DAC converters, and crystal memory displays.
I2C is yet another synchronous serial protocol like SPI, but with several advantages over it. These include the ability to have multiple masters and slaves, simple addressing no need for Chip Select , operating with various voltages, and using only two wires connected to two pull-up resistors.
With the rise of parallel and many wireless protocols, serial communications have never fallen out of popularity. Generally using only two to four wires for transmitting and receiving data, serial protocols are an essential mode of communication for electronics that only have a few ports to spare.
Another reason is its simplicity which translates to reliability. With only a few wires sending data once at a time, serial has proven its reliability to send the complete packets of data without any loss or corruption when transmitted. Even at high frequencies and longer range communication, serial protocols still beat many modern parallel communications protocols available today.
Although many might think that serial communications like UART, SPI, and I2C have the disadvantage of being old and outdated, the fact remains that they have proven their reliability over several decades.
Protocols being this old without any real replacement only suggests that they are, in fact, indispensable and will continue to be used in electronics for the foreseeable future. Here's what you need to know. Craving to learn how things worked, Jayric Maning started tinkering with all kinds of electronic and analog devices during his earlier teens.
He took up forensic science at the University of Baguio to where he got acquainted with computer forensics and cyber security. He is currently doing lots of self-study and tinkering with tech figuring out how they work and how we can use them to make life easier or at least cooler!
What Is Serial Communication? Before the UART device can send data, the transmitting device converts the data bytes to bits. After converting the data into bits, the UART device then splits them into packets for transmission.
Each packet contains a start bit , a data frame , parity bit , and the stop bits. Figure 2 shows a sample data packet. If there are no errors in transmission, it will then proceed to strip the start bit, stop bits, and parity bit to get the data frame. It may need to receive several packets before it can rebuild the whole data byte from the data frames.
After rebuilding the byte, it is stored in the UART buffer. The receiving UART device uses the parity bit to determine if there was a data loss during transmission.
Data loss in transmission happens when a bit changed its state while being transmitted. Bits can change because of the transmission distance, magnetic radiation, and mismatch baud rates, among other things.
UART has settings that need to be the same on both devices to have proper communication. These UART settings are the baud rate , data length , parity bit , number of stop bits, and flow control. We need to set both UART devices with the same baud rate to have the proper transmission of data. Common values for baud rate are , , , , , , , and bps. The possible setting for Parity Bit is Odd or Even. UART devices can use none , one or two stop bits to mark the end of a set of bits called packets transmitted.
Arduino has one or more UART pins depending on the board. So if you will upload sketches to your UNO, be sure to first disconnect any wires on pins 0 and 1. The UART logic levels may differ between manufacturers.
A push-button wired to the first Uno board will control the built-in LED of the second Uno board and vice versa. If you want to learn more about the Arduino, check out our Ultimate Guide to the Arduino video course. After gathering and assembling the hardware, we are now ready to program our boards.
For this project, both boards will have identical sketches. As always, the Arduino makes it easy for us to use the built-in UART hardware by using the serial object. To communicate via the UART interface, we need to configure it first. The speed parameter is the baud rate that we want the UART to run.
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