Let us know about data transmission:
It is the process of sending the data between digital devices. In analog or digital format the data is sent from one node to another node. Devices will communicate with each other by sending the data to each other.
Data will be sent using the bits between digital devices. There are 2 methods which are useful for transferring the data:
- Serial transmission
- Parallel transmission
In serial transmission, data will be sent one by one at a time through a single channel. In parallel data, multiple data bits will be sent at the same time through multiple channels.
Serial communication consists of the process in which we send the data “one bit sequentially at a time” and It uses a communication channel or system bus for sending these bits. Parallel communication is in contrast with serial communication, in parallel communication we send many bits like a whole, through a link that has many several channels. Long-haul communication is used by serial communication and also most computer networks use these serial communications.
The cable cost and also synchronization difficulties will make impractical for parallel communication.at shorter distances the serial computers are becoming common. They have signal integrity which is improved and the speed of transmission will be in new serial technology and it has simplicity and there is no need of serializer and de- serializer which has disadvantages.
For transferring the data the serial communication systems were designed originally over long distances by suing some data cable.
The transmission of data happens in all long-distance communication one bit at a time but not in parallel, it will reduce the cable’s cost. Carrying of the data by the cables and they plug computer plugs into are given a specific name which reduces the confusion.
The serial connections are keyboard and mouse cables and ports are serial like PS/2 port, Apple desktop bus, USB.
The digital videos which are carried by the cables are serial, like coax cable gets plug into the HD-SDI port, firewire port ethernet cable which connects to an IP camera and also FPD link etc.
Serial ATA transmits the data one bit at a time serial CSI are also the examples and ethernet cable which is plugged in the ports of ethernet, DVI port or the HDMI port.
Two integrated circuits are connected using communication systems on the same printed circuit board, which are connected using signal traces on the board but not external cables.
The expensive circuits are integrated circuits if they have so many pins. for reducing the pins which are there in the package serial buses are used by ICs for transferring the data when the speed is not needed. Low cost serial buses are RS-232, SPI, I2C, UNI/O,1-wire and PCI express etc.
in serial transmission, it has 2 classifications:
1 is asynchronous and second is synchronous.
Asynchronous serial transmission:
Sending of data bits can be happened at any point of the time. Between data bytes the start bits and stop bits are used for synchronizing the transmitter and receiver useful for transmission of data properly. Sending and receiving the data bits takes time and that time is not constant, for providing the time gaps are there between the transmissions.
No synchronization will be used in the asynchronous mode of transmission and this is the advantage of the asynchronous mode of transmission. It is an effective method for costs. In this the data transmission will be slower and that is the disadvantage of asynchronous mode of transmission. And this is always not the case.
One device that wants to communicate with another device, will send the data using digital pulses through serial communication wires, this happens when the protocol supports. That is how communication starts. The pulses are picked up by the receiving device, they look for the device which comes in the exact rate.
This is asynchronous serial communication. In this it does not require a timing clock in which sending and receiving happen using train of pulses and both the devices will run at the same time, the timing will be different for both the devices.
The microcontroller which uses instruction will need a timing clock, it is on proper timing it uses quartz crystal in this the instruction cycles will run properly. Each and every device will listen not depending on each other and will send the pulses which are digital and they will represent data on the exact time.
If transmission of data happens at the same time and receives at the same time which is known as duplex communication, half-duplex means it works like a walkie-talkie. Only single device will communicate at a time and the turns will be there for transmission between the devices.
sometimes we may only need devices for monitoring or for receiving, in those situations the half duplex works well. Speakerphone is also an example for half duplex. Asynchronous mode pf transmission is also known as transistor-transistor logic(TTL) serial the logic 1 is high voltage level, and 0 is low voltage level. One universal asynchronous receiver transmitter(UART) will be there for every microcontroller.
For consumer use, the serial communication is replaced with USB which is universal serial bus. The serial communication is used by microcontroller development for programming the microcontroller through the serial port which used PC. For doing this we need cables which are USB-to-serial converter. The examples are FTDI’S USB to RS232 and it is a serial protocol which is used in PCs and it is very famous and it will use inverted logic.
For the successful communication, the devices are set up properly using proper time and the communication must be understood on the both side of devices. The devices which are in the communication should have things in common:
The voltage level should be interpreted in the same way by both the devices with serial train of pulses. agreeing on the level of voltage which is representing the 0 bit and which is representing 1 bit is important.
Representing which has higher voltage and which has low voltage is very much needed.
Three wires must be shared:
For measuring the voltage levels, a common reference point is ground.
Transmit line is the sending of data or called transmitter.
Receiving line is receiving the data or called receiver.
Now let us know about synchronous serial transmission:
Transmission of data in a continuous stream in time by using a master clock. A synchronized clock frequency is used between both transmitter and receiver, start and stop bits are also used and the gaps are not there. Data will be moving fast and the error will be happening very less frequently because there is synchronization of transmitter and receiver time.
Data accuracy is synced and also dependent on the timing that happens between the devices, this synchronous mode of transmission is expensive. It consists of synchronized clocks that are between the devices and they are present on the serial bus, and the data is transmitted between the devices.
It will remove the requirement of start and stop bits and it will increase the throughput. Serial peripheral interface is the serial communication protocol it will use the sharing clock line which is useful for synchronization purpose and also it functions at rate bits which will exceed 10MHz.
The serial peripheral interface(spi) is useful for sending the data between many devices. Master and slave configuration will be there and these devices are arranged in them.
Master will control the slaves and slaves will be receiving the instructions from the master the configuration consists of one device as the master and the slaves are the remainders, SPI will be useful for sending the data and will be receiving the information that has higher transfer data rates and they are useful for shorter distances which are board-level communication.
The communication happens between many devices and this is the main advantage of SPI. There is a higher transfer date rates comparing to other communications interfaces and also enables the data to be transmitted and received. SPI wants many signal lines and signal wires comparing to other type of communications. No standard message protocol will be there in SPI.
SPI communication has 4 signals the signals names are MOSI(Master out-slave in), MISO(master in slave out), SCLK(serial clock), CS(chip select)
Clock signal: the master device generates the clock signal which has frequency specifically and it is useful for synchronizing the data which needs to be sent and received between the devices.
The configuration happens using the master and also uses properties like CPOL(clock polarity) and also clock phase(CPHA). Polarity of the clock signal will be determined using CPOL. And it can either be low or high that is 1 or 0 bits are given.
A clock signal which is of low it has a higher pulse rate and leading-edge will rise and a clock signal that has 1 it has a lower pulse rate and the leading edge will be falling.
MISO AND MOSI signals:
The SPI communication uses these two signals and MOSI will send the data out from the master and the slaves will receive the data, MISO will send the data from the slaves and the master device will receive the data.