Saturday, August 13, 2011

Development of the WebCell Begins

On April 20, 2007 I started my project to make a web server based on an Atmel AVR microcontroller. Let me start catching up on this story.

The idea that it was possible to build a web server around a microcontroller unit (MCU) came from a series of articles written by Peter Best that appeared in Nuts and Volts magazine in 2006. These articles discussed network protocols, and also led me to EDTP Electronics and their “Easy Ethernet” modules for experimenters.

The “Easy Ethernet” line was available with either a Microchip PIC or Atmel AVR MCU. I had used the PIC in the distant past, but switched to the AVR once I heard about it – I consider it vastly superior. So my module has the Atmel ATmega16 MCU, which has 16K of program space and 1K of RAM. The Ethernet chip on the module is the Realtek RTL8019AS.

Easy Ethernet AVR module from EDTP Electronics. The shiny block at the upper left is the Ethernet jack. Strangely, the module did not come with a connector for Atmel’s standard debugging interface (JTAG), so I had to patch into the correct pins using the “squid”.

I spent about seven days working on the project over the next six weeks. I was writing basic drivers for the Ethernet chip and implementing the Address Resolution Protocol (ARP) as my first test. On June 3rd I hit my first milestone, verifying for the first time the module could send and receive Ethernet frames: it successfully made an ARP request and read the response.

I continued to work on the project a little on and off until later that summer, when I dropped it to do other things.

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