Sunday, 28 December 2014

AVR 28-pin Development Board with USB support

So i made a development board for the 28-pin AVR micro-controllers like the ATMEGA 8, 168p, 328p etc. some time ago.

I made my design after i found the Metaboard

The metaboard design fascinated me in that it was a AVR development with built-in programmer(i.e. Usbasploader support)  and also we could upload code from Arduino directly and we can also use the USB interface on-board with the V-USB library.

But i had some extra requirements like a 3.3v regulated supply on-board. Also i did not want to sacrifice 2 pins for the USB connection so added a dip switch to disconnect them whenever necessary and some other changes as mentioned below:-

  1. Added an led which was connected to a digital I/O as well as PWM pin.
  2. Added an extra 47uF capacitor close to VCC and GND pins.(Required to compensate ground bounce when driving motors using L293D or any other motor drivers using the same supply that powers the dev board)
  3. Extra regulation filter capacitor added for power supply stability.
  4. Added a 10uH inductor for AVCC as specified by Atmel Docs for cleaner ADC.
  5. And finally as you can notice in the picture above every I/O pin has dual sockets(both male and female, you will understand the advantage only when you face the need).
You can say that my design is a bit overloaded design with whatever i could possibly add of whatever features i required.

Best of all i have tried to keep the PCB still a Single-sided one so that most people can still build it at home using toner-transfer method and common etching techniques.

Here is the layout (Warning! its not to scale, use pdf from github design files link given below)and :

and this is the schematic :

You can get the board design files from here It was made using Eagle Cad software. You are welcome to make any modifications if you like.

Unknown An Electronics and Tech Enthusiast

I am a Tech enthusiast who loves to build stuff like new gadgets and tinker around with electronic devices doing some DIY stuff, writing some code and in the process providing something back to the community.

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