The CodeVisionAVR IDE features a builtin InSystem AVR Chip Programmer, which allows automatic programming after a successful compilation. Learn how to generate PWM signals of varying duty cycle to control LEDs, Motors etc. A demo program in C for Atmel Studio6 is also provided for quick testing. ATMEL AVR Tutorial 2 How to access Input Output Ports Tutorial Overview You cannot imagine to use microcontroller without using any of its io pins. Finally its all about  taking input, processing it and generating output Thus io registers and their correct settings is indispensable part while learning to program any u. C. We will learn how to use Atmel AVRs GPIO ports and actually code  for writingreading data tofrom port pins in this AVR tutorial. It is slightly confusing for beginners, however once you understand it, you will certainly appreciate the way it is designed. To get quick background about AVR microcontrollers, refer to Intoduction to AVR Tutorial on this blog. NOTE I will frequently refer to  configuring pin or simply pin. Remember, a port has multiple pins. CodeVisionAVR.jpg' alt='Codevisionavr Serial' title='Codevisionavr Serial' />Thus in order to change setting for one port, you have to change setting for all port pins of that port. To change setting for one single pin of the port, you have to change a particular bit in associated register. Got that If not read this para again. Registers. Atmel AVR is 8 bit microcontroller. ROOT/kaf/ksm/sayt2/user-images/image007.png' alt='Codevisionavr Serial' title='Codevisionavr Serial' />All its ports are 8 bit wide. Every port has 3 registers associated with it each one with 8 bits. Every bit in those registers configure pins of particular port. Bit. 0 of these registers is associated with Pin. Bit. 1 of these registers is associated with Pin. These three registers are as follows x can be replaced by A,B,C,D as per the AVR you are using DDRx register PORTx register PINx register. DDRx register DDRx Data Direction Register configures data direction of port pins. Means its setting determines whether port pins will be used for input or output. Writing 0 to a bit in DDRx makes corresponding port pin as input, while writing 1 to a bit in DDRx makes corresponding port pin as output. Example to make all pins of port A as input pins DDRA 0b. A as output pins DDRA 0b. B as output and higher nibble as input DDRB 0b. Poser S Models. PINx register. PINx Port IN used to read data from port pins. In order to read the data from port pin, first you have to change ports data direction to input. This is done by setting bits in DDRx to zero. If port is made output, then reading PINx register will give you data that has been output on port pins. Now there are two input modes. Either you can use port pins as tri stated inputs or you can activate internal pull up. It will be explained shortly. Example to read data from port A. DDRA 0x. 00 Set port a as input. PINA Read contents of port a PORTx register. PORTx is used for two purposes. To output data    when port is configured as output. When you set bits in DDRx to 1, corresponding pins becomes output pins. Now you can write data into respective bits in PORTx register. This will immediately change state of output pins according to data you have written. In other words to output data on to port pins, you have to write it into PORTx register. However do not forget to set data direction as output. Example to output 0x. FF data on port b. DDRB 0b. 11. 11. PORTB 0x. FF write data on port to output data in variable x on port a. DDRA 0x. FF make port a as output. PORTA x                output variable on portto output data on only 0th bit of port c. DDRC 0b. 00. 00. PORTC 0b. To activatedeactivate pull up resistors when port is configures as input. When you set bits in DDRx to 0, i. PORTx register are used to activatedeactivate pull up registers associated with that pin. In order to activate pull up resister, set bit in PORTx to 1, and to deactivate i. In input mode, when pull up is enabled, default state of pin becomes 1. So even if you dont connect anything to pin and if you try to read it, it will read as 1. Now, when you externally drive that pin to zeroi. However, if you configure pin as tri state. Then pin goes into state of high impedance. We can say, it is now simply connected to input of some Op. Amp inside the u. C and no other circuit is driving it from u. C. Thus pin has very high impedance. In this case, if pin is left floating i. If you try to read corresponding bit in pin register, its state cannot be predicted. This may cause your program to go haywire, if it depends on input from that particular pin. Thus while, taking inputs from pins using micro switches to take input, always enable pull up resistors on input pins. NOTE while using on chip ADC, ADC port pins must be configured as tri stated input. Example to make port a as input with pull ups enabled and read data from port a. DDRA 0x. 00 make port a as input. PORTA 0x. FF enable all pull ups. PINA read data from port a pinsto make port b as tri stated input. DDRB 0x. 00 make port b as input. PORTB 0x. 00 disable pull ups and make it tri stateto make lower nibble of port a as output, higher nibble as input with pull ups enabled. DDRA 0x. 0F lower nib output, higher nib input. PORTA 0x. F0 lower nib set output pins to 0, higher nib enable pull ups. Chuzzle Deluxe Games No. Summary. Following table lists register bit settings and resulting function of port pins. Note Convention of x. You need to use appropriate AND, OR, and bitshift lt lt, operations to extract the desired bit field. DDRx. n. PORTx. n. PINx. ntri stated input. PINx. n pull up input. PINx. n output. 1write data bit. PORTx. n x writing 1 toggles thestate of the output pin. PINx. n 1 Hands on You can type following programs in Code. Vision. AVR or Atmel Studio and test them on your development kit. To know, how to burn code into u. C using Pony. Prog. Making and Using Simple AVR Programmer. You can also use USBasp and Avrdude to program AVR controllers. Refer to the Avrdude tutorial to understand how to downloadburn programs on AVR microcontroller. If you dont have development kit, simply connect 8 LEDs to PB i. In Project Configure C compiler do not forget to set following options Chip   ATmega. Clock 1. 6MHz or whatever you are usingExperiment with these programs and try to learn more from it. Blink LED on PB0 at a rate of 1. Hz. include lt mega. DDRB 0x. FF PB as output. PORTB 0x. 00 keep all LEDs offwhile1. PORTB 0b. LED off. PORTB 0b. 00. 00. LED on. delayms5. Blink LEDs on PB with  different patterns according to given input. Kit use SW0, SW1 No Kit Connect a 2 micro switches between pin PC0,PC2 and ground. So that when you press the switch pin is pulled low. DDRB 0x. FF PB as output. PORTB 0x. 00 keep all LEDs off. DDRC 0x. 00 PC as input. PORTC 0b. 00. 00. SW0 is pressed show pattern 1ifPINC 0b. PORTBp. 1i output data. PORTB0 turn off all LEDs. SW1 is pressed show pattern 2ifPINC 0b. PORTBp. 2i output data. PORTB0 turn off all LEDs. Other AVR Tutorials atmel avr avr gpio pin ddr port tutorial. Total 2    Average 3.