PICcoder

This article attempts to explain simply how to create a Ethernet Developement board and to document my own experience of building one. The board uses a PIC18LF4620 and a ENC28J60 ethernet controller from Microchip. It runs a slightly modified version of the Microchip TCP/IP Ethernet Stack.

This design requires the LF variant of a PIC, eg an 18LF4620 not a 18F4620

Please note all code is released AS-IS and should used at the users own risk, no garentee is made by PICcoder.co.uk or the author with regards to the accuracy of the diagrams or code contained in this article.

Discuss this article on the forums. (87 posts)

Hardware

To build a developmment board you will need:

• Download the Microchip TCP/IP Stack from the microchip website
• Download a C complier for the PIC (e.g the microchip MCC18 complier)
• A PIC programmer, (I use a copy of the Microchip ICD2)

The board is made up of a PIC microcontroller connected to an ethernet controller (ENC28J60 from Microchip). The PIC and ethernet controller are connected by an SPI bus, a reset line and a chip select wire. The ENC28J60 does have an interrupt line and a wake on lan output but they aren't used in this implimentation, the Microchip TCP/IP stack doesn't need interrupts, it polls the ethernet controller regularly and divides its various tasks up into short chucks which it runs cooperatively.

Circuit Diagram

Click on the schematic for a detailed version

To simplify the board I run everything on 3.3 volts from a variable power supply. I'm about to add a voltage regulator to stablize the input voltage which varies a bit from from my old power supply and sometimes crashes the board.

To run at 3.3 volts the PIC has to be one of the LF variants and can only run upto about 25 Mhz. You can find the limit by looking at the graph of maximum clock frequency against supply voltage, in the datasheet for your particular PIC. I run my board at 24Mhz purely because I happened to have a 24Mhz crystal lying about.