The second step in any project is to identify the main components that are needed to make your goals play out. In this case I have chosen a Microchip PIC24F series Microcontroller as the core of my project supplemented with a Microchip ENC28J60 Ethernet controller to handle the MAC and Physical layers of the Ethernet interface .
The PIC24F series has many advantages over its 10, 12, 16, and 18 series cousins, First and foremost the 16 bit architecture allows the chip to have a far expanded instruction set which makes it much more viable to program the chip in a higher level language such as C or even BASIC. I myself will be using Microchip’s student version of its C30 Compiler which comes fully loaded with individual header files for each chip in the 24 series and even libraries to help out with the on chip hardware peripherals like USART, I2C, SPI, Etc. The 24 series also has one advantage that most people tend to overlook, its hardware peripheral pins can be remapped to almost any pin on the device, meaning much less time working on routing a PCB. Its also interesting to notice the distinction between the 24F and 24H series controllers, while the 24H controllers can typically run at much higher speeds achieving in the range of 64mips, it typically lacks the expanded peripherals of the 24F series which on average has about double the hardware peripherals of the 24H series but performs at only around 16Mips
The exact model I’ll be using in this case is the PIC24Fj64GA002 with 64K of flash memory, 2 hardware SPI interfaces, and a max speed of 32Mhz (16Mips).
I wont be writing a guide for using the pic24 however I was able to find an excellent tutorial for any interested.
The ENC28J60 Ethernet controller handles everything below the network layer of the standard OSI Model, it handles the media access control layer and the physical reception and transmission of packets. The ENC28J60 interfaces to a main controller via SPI and receives and transmits information via an internal 8k buffer operating in a FIFO fashion. the ENC28J60 supports full and half duplex modes as well as unicast, multicast, and broadcast packets. It is also fully compatible with all 10/100/1000 Base-T networks making it a very plug and play device. The only qualm I have about it is that it it doesn’t support auto-negotiation which means its not safe to use full-duplex mode unless you can manually change your switch port to full-duplex.
During the course of this project I will be entering a lot of new territory, I have never before used a 16 bit uC, I have never before coded a Microcontroller in C, (until now I have only used the 8bit 12 and 16 series microchips and coded them in Assembly or PIC Basic), I have also never used the SPI hardware peripheral which many PIC’s provide and I have absolutely zero experience with the ENC28J60 module. So this project will without a doubt put me in a position to learn some new things.
Below I have included a schematic and board layout for a pic24 28Pin SOIC breakout board with an ICSP header for programming, A useful tool for familiarizing yourself with the PIC24 Series
