| Image may be NSFW. Clik here to view.  |
| Serial Communication tutorial |
This tutorial focuses to teach you how to program Serial Communication (UART) in AVR Microcontrollers. UART plays an important role in almost every embedded applications which we see in our day to life and hence it was considered to be very important concept in every Microcontroller.
The above design demonstrates the usage of UART to send and receive data via hyperterminal as well display the received data in 1 16x2 LCD. As we all know Microcontroller works in TTL logic which is not compatible with the PC so we have to employ a level converter IC MAX232, read more about the working of IC MAX232.
REGISTERS USED:
In AVR there are five registers which are meant to use for Serial Communication such as UDR, UBBR , UCSRA, UCSRB, UCSRC. Lets see the functions of these registers briefly.
UDR:
| Image may be NSFW. Clik here to view.  |
| UDR Register |
UDR or USART Data Register is meant for writing and receiving the data through the UART. In this there are two shift registers referred to as Transmit Shift register and Receive Shift register with each having a separate buffer register. When the data is written to UDR it will be transferred to Transmit Data buffer register and when we read the contents of the Receive Data buffer register is returned.
UBBR:
In AVR the baud rate of the UART is programmable and it is achieved by means of this UBBR register. It is 16 bit register classified into lower UBBRL and higher UBBRH out of which 12 bit is usable The formula governing the relation between the value of UBBR and Oscillator is
Baud Rate = (Oscillator Frequency / (16( UBBR Value +1))
So for a 8MHz oscillator frequency and 9600 baud rate the value need to be loaded in the UBBR will be
UBBR = (8MHZ /16(9600))-1
=(500KHz/ 9600) - 1
= 51 ( equivalent hex 33)
UCSRA:
| Image may be NSFW. Clik here to view.  |
| UCSRA Register |
UCSRB:
| Image may be NSFW. Clik here to view.  |
| UCSRB Register |
UCSRC Register:
| Image may be NSFW. Clik here to view.  |
| UCSRC Register |
STEPS TO PROGRAM UART:
- Load the hex value in the UBRR Register for the Baud rate you are about to use.
- Set the bits in the registers UCSRA, UCSRB & UCSRC based on your usage requirement.
- For Transmission Place the data in the UDR register and check for the appropriate flag to set in the UCSRA regsiter
- Clear the Flag for further transmission.
- For receiving the data, wait for the Receive flag to set in the UCSRA register and then read the UDR register to obtain the received data for processing or display.
- Clear the Flag for further data reception.
CODE:
The below code is built using AVR studio software. This code demonstrates both transmission and receiving the data. Initially controller send data "BGN" to the hyperterminal and then prepares itself to receive data which is made to print in a 16x2 LCD.
|
Like this tutorial? Share this with others through social sites and do not forget to follow us there for more of these. Post your comments and queries below, we will get back to you as soon as possible.
Image may be NSFW.
Clik here to view.![]()
Image may be NSFW.
Clik here to view.![]()
Image may be NSFW.
Clik here to view.![]()
Image may be NSFW.
Clik here to view.![]()
Image may be NSFW.
Clik here to view.![]()
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Image may be NSFW.Clik here to view.
Clik here to view.
