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1. Atmega8 Uart Program Application
2. Atmega8 Uart Code
3. Atmega8 Uart Program In Uae

Mar 02, 2009 Another issue 'for another project' is that I have another micro-controller atmega8L that I want to use it's internal oscillator of 8MHz with baud rate 9600 in the UART but when I program it and test it nothing is coming out of the TX and nothing is going into the RX even though I enabled the TX and RX in the code and I doubled checked the.

1. I have written a program in VC to send an 'a'. (FTWRITE) Now the TX from the ftdi2232C is connected to the RX of the Atmega8 (on the SDK EvolationBoard) and inverted. If the Atmega receives an 'a' it should send for example '12345' back. How can i check, if there is new data availible in the receive buffer for the FTDI?
2. Programming software. So it was common to throw a pre-programmed ethernet “coprocessor” on it and just bit/byte bang as you would with a UART. Arduino vs avr atmega8 its comparing.
3. Learn, How to use Interrupt with UART.UART interrupt programming (atmega8 / atmega16 /atmega32 )#download code and proteus pro.

This tutorial focuses to teach you how to program AVR Serial Communication (UART). 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 16×2 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 SERIAL COMMUNICATION:

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:

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.

UBRR:

In AVR the baud rate of the UART is programmable and it is achieved by means of this UBRR register. It is 16 bit register classified into lower UBRRL and higher UBRRH out of which 12 bit is usable The formula governing the relation between the value of UBRR and Oscillator is

Baud Rate = (Oscillator Frequency / (16( UBRR Value +1))

So for a 8MHz oscillator frequency and 9600 baud rate the value need to be loaded in the UBRR will be

UBRR = (8MHZ /16(9600))-1

=(500KHz/ 9600) – 1

= 51 ( equivalent hex 33)

UCSRA:

UCSRB:

UCSRC Register:

STEPS TO PROGRAM UART:

1. Load the hex value in the UBRR Register for the Baud rate you are about to use.
2. Set the bits in the registers UCSRA, UCSRB & UCSRC based on your usage requirement.
3. For Transmission Place the data in the UDR register and check for the appropriate flag to set in the UCSRA regsiter
4. Clear the Flag for further transmission.
5. 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.
6. Clear the Flag for further data reception.

CODE:

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If You come there from internet search i assume You already know what is PWM and where it can be used, so in this post I’ll only explain how to use 8 bit timer in Atmega8 to generate PWM signal and control frequency, polarity and duty cycle.

PWM can be generated from 16-bit Timer/Counter1 or 8-bit Timer/Counter2 but this time I’ll only explain 8-bit Timer/Counter2Fast PWM Mode.

In this picture from Atmega8 documentation Fast PWM mode is explained. Counter(8bit) counts from 0x00 to 0xFF and restarts from 0x00. In not inverting mode OC2 is cleared when counter match value in OCR2 register and set at 0x00. In inverting mode OC2 is set when counter match value in OCR2 register and cleared at 0x00.

From this all turns out that PWM duty cycle depends on OCR2 register. In not inverting mode duty cycle = OCR2/256*100% and it’s 50% if OCR2 is 0x80(middle between 0x00 – 0xFF).

In every PWM period counter must count 256 steps, so frequency of signal is 256 times lower than counter clock from prescaler. PWM frequency = Atmega clock frequency/timer prescaler(1,8,32,64,128,256)/256. With 4 MHz crystal maximum(without prescaler) PWM frequency is 15 625Hz.

Register setup

For example 15 625 Hz, 50 % duty cycle, non-inverting mode PWM signal generation.

1. OCR2=0x80(128); As mentioned before duty cycle = OCR2/256*100%

Atmega8 Uart Program Application

2. TCCR2=0x69;

3. DDRB=0x08; PWM signal is outputted by toggling level of PORTB pin 3.

DDRB sets it as output.

All together:

#include <iom8.h>
int main( void )
{
DDRB=0x08;

OCR2=0x80;
TCCR2=0x69;
while (1) {};
}

Result:

~10% duty cycle, 61 Hz.

#include <iom8.h>
int main( void )
{
DDRB=0x08;
OCR2=0x1A; // 256/10=25,6 26 in hex = 1A;
TCCR2=0x6E; // 256 prescaler


while (1) {};
}

Result:

Atmega8 Uart Code

And there is demo program and *.hex file for PWM demo seen in video.

Atmega8 Uart Program In Uae

Atmega8 PWM demo program (1.8 KiB, 8,281 hits)