{"id":8989,"date":"2014-12-21T01:53:14","date_gmt":"2014-12-21T06:53:14","guid":{"rendered":"http:\/\/embedded-lab.com\/blog\/?p=8989"},"modified":"2016-12-18T19:46:16","modified_gmt":"2016-12-19T00:46:16","slug":"xmega-io-ports","status":"publish","type":"post","link":"https:\/\/embedded-lab.com\/blog\/xmega-io-ports\/","title":{"rendered":"XMega I\/O Ports"},"content":{"rendered":"

Any microcontroller must have I\/O pins for taking inputs and providing outputs. The ATXMega32A4U just like any other micro has 34 programmable I\/O pins divided unevenly amongst six IO ports. Most I\/O ports are 8 bit wide. XMega I\/Os have digital, analog and special purpose functions. Some I\/O pins have more than one use. A quick view of the XMega I\/O pins reveals the purpose of these pins.<\/p>\n

\"XMega<\/a><\/p>\n

I have always admired Atmel\u2019s documentations, particularly datasheet and reference manuals. They are highly user friendly and when it comes to XMega\u2019s documentations, there is one word I can say \u201cAwesome\u201d. The reference manuals and documentations of XMega devices come in colours, legends and bookmarks and so navigating these docs is pretty easy provided that one knows how to use PDF reader like the Adobe Reader efficiently.<\/span><\/p>\n

XMega devices are not same as Mega\/Tiny AVRs. People who have been using Mega\/Tiny AVR will find similarities but not monotony. In Mega\/Tiny AVRs there are basically three registers to make an I\/O pin\/port work and these are DDRx<\/i><\/b>, PINx<\/i><\/b> and PORTx<\/i><\/b> registers. In XMega devices this concept is expanded, allowing more options in designs and coding. People who had played with ARM micros will also find some interesting similarities. Trust me I played with STM32 and AVR micros and I found some striking similarities. These similarities are as such that I can literally anticipate what I\u2019ll find next when I proceed. One such similarity is the alternate function of an I\/O pin. This basically allows general purpose I\/O pins to do stuffs other than the basic use as a general purpose I\/O. Pin remapping is another feature that is common in both XMega and ARM micros. Unlike traditional micros which have dedicated pins for certain internal hardware modules like USART, I2C, SPI, etc. both XMegas and ARMs have an option to relocate dedicated hardware pins from one pin\/port position to another. Thus hardware designing become more flexible and easy. It is just why we feel comfortable making stuffs with embedded systems rather than using complex discrete mixed analog-digital circuits. Just imagine, by mistake you wired USART pins wrongly in your design but those I\/O port pins\u2019 can be alternatively used as USART pins. This is where you get saved by pin remapping rather than remaking the entire hardware stuff or even making cuts and rewires in the PCB. In a sense pin remapping is a hardware level coding rather than software level coding though this remapping is itself done with a few lines of code.<\/p>\n

Before we proceed, I would like to remind readers that in my previous post I stated that Atmel\u2019s software library support allow AVR studio users to code more easily as their header file replaces constants with meaningful names and purposes. As of now MikroC for AVR doesn’t enjoy the fruits offered by Atmel. I realized that I should adopt this feature in MikroC to save both time and efforts, and so I made my own header files containing these constants. Once we enter the code arena we\u2019ll understand how these files come to work. At the time of writing I have just made two such headers \u2013 one for the clock system which I previously explained and the other for I\/O ports as this will be needed here. I’m expanding the collection of such header files on hardware basis and hopefully I’ll share them in the upcoming posts.<\/p>\n

I\/O Pin Configurations<\/h2>\n

I\/O pins in XMega devices have more than the usual general purpose input\/output functionality. Shown below are the six possibilities. Wired-AND, Wired-OR and Bus-keeper configurations have limited uses while Totem-pole I\/Os are mostly used.<\/p>\n

\"IO<\/a><\/p>\n

 <\/p>\n

Any XMega reference manual\/datasheet briefly describes I\/O port configurations but those descriptions are not enough to completely get ideas on how they behave in real world applications. Some people even get confused with the nomenclature of the configurations.<\/p>\n