January 19th, 2009

Ethernet relay board

Ethernet relay board

There many devices which can be controlled trough relays, like light bulbs, pumps, motorized doors, and the list can go on. Most of the relay boards available on the web are based on the serial interface, this has some drawbacks: limited distance, about 15meter based on the RS232 standard, and the new generation of motherboards lack this port. The presented board has ethernet interface using the ENC28J60 and the PIC18F4680, it also has a Real Time Circuit with battery backup, the ethernet interface beside its speed has a major advantage, the RJ45 contains a coupling transformer which is used to galvanically isolate the local electronics ground from the bus, this doesn’t mean that it will support a 230 common mode voltage, but offers protection to a certain limit.

The ethernet interface shows its full potential when comes along with a webserver, fortunately the author thought this to, he developed a simple web server which runs on the PIC, this way you can control the relays trough your network or even the internet.

Ethernet relay board: [Link]

July 15th, 2008

Webserver Based On ATMega88

Webserver Based On ATMega88

Before starting this Ethernet project the author did of course some prototyping and then he noticed alreadythat UDP was not a problem with lots of space left on the atmega88. Therefore he was quite confident that TCP + HTTP will work. TCP/IP was invented more than 25 years ago. Todays microcontrollers provide almost the computing power a standard computer had at that time. No java or xml was used at that time. Things were done in smart and efficient ways.

As you can imagine this web-server code is written for a friendly environment. Don’t put it on the open internet. The code uses e.g the incoming packet to build from it the outgoing packet. An attacker who sends a mal formed IP packet might be able to confuse the TCP/IP stack. The code is verified with a lot of different browsers and a number of operating systems. It was tested Linux, BSD Unix, Win 98, Win XP, Mac OS-X with a number of different web browsers. It works very well but it was not tested agains atacks and destroy tests.

Webserver Based On ATMega88: [Link][via]



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