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The HPC Explorer is a small low-cost demo board from Microchip for the High Pin Count general purporse PIC18FXXX family of microcontrollers.

The board includes a 80-pin PIC18F8722, a potentiometer, RS232 serial interface, one user pushbutton, some LEDs and a header connector for PICtail add-on boards.

The HPC Explorer can also be used to evaluate the PIC18 J-series 3V devices available in a Plug-In Module that fits in the header connectors around the existing MCU.

Microchip offers an Ethernet PICtail board that can be connected directly into the PICtail interface available in the HPC Explorer. Be aware that there are two different models of the Ethernet PICtail, the regular one and the "Plus" which is smaller, only 3.3V and intended for boards such as the Explorer 16 with a complete different PICtail interface.

This project will show you how to configure the HPC Explorer board to be able to run a modified version of the latest Microchip TCP/IP stack.

Design considerations

I don't have an Ethernet PICtail and unfortunately the HPC Explorer does not provide any area on the PCB for prototyping, I decided then to put together a small adapter board to use the PICtail interface to interconnect the HPC Explorer with the nic28 ENC28J60 board from LJCV Electronics and add an 8-pin socket for a serial SPI EEPROM such as the 25LC1024 or the lower capacity 25LC256.

Initially I used the +5V supply available on the PICtail interface to power the ENC28J60 on the nic28 and the serial EEPROM, but while the voltage regulator on the HPC Explorer can handle the load its package is SOT-223 with almost no copper on the board to permit a reliable thermal dissipation, then I added an external 5V regulator on the adapter board and modified the HPC Explorer cutting the +5V line going to pin 26 of the J3 connector and added a wire from that pin directly to the output of the CR1 bridge rectifier.

Click for a larger image Figure 1
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Click for a larger image Figure 2
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Click for a larger image Figure 3
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Figure 1 shows all the different pieces, the HPC Explorer, the adapter board and the nic28, Figure 2 a close up of the adapter board and Figure 3 the nic28 mounted on the adapter board and the whole thing mounted on the PICtail interface connector J3.

Figure 4 below shows a detailed schematic of the PICtail adapter board.

Figure 4
[Click on the image for a larger view]

Getting the board up and running

Compiling the firmware is not a huge or complicated task, it requires few software tools available for download from Microchip's website at no cost, and obviously the TCP/IP stack source code distribution and a PIC programmer. For this project I used Microchip's MPLAB ICD2 as a programmer.

With the latest modified version of the Microchip TCP/IP Stack v3.75, the process is quite simple.

This new version adds the HPC_EXPLORER macro definition that combined with the device selection for the Microcontroller generates the appropriate code for this particular project.

The software distribution includes the MPLAB IDE project file HPC_EXPLORER.mcp, load this project into MPLAB IDE, select the correct processor (by default the project has selected the PIC18F8722) and verify that the settings on the config.h and hpc_explorer.h files apply to your project or modify them accordingly (both files are located in the include subdirectory of the main src directory).

For additional details check the README.TXT file included in the software distribution.

For a detailed explanation about how to build Microchip's TCP/IP stack for this or similar projects
Click Here.

Schematics & Firmware source Code

Microchip HPC Explorer Schematics (Rev.5)  
Microchip Ethernet PICtail Schematics (Rev.5)  
PICtail-nic28 Adapter Schematics  
Building the Microchip TCP/IP Stack for this project  

Datasheets for relevant parts used in this project

Microchip's PIC18F8722 8-bit MCU Datasheet  
Microchip's HPC Explorer Product Page  
LJCV Electronics nic28 Product Page  
Microchip's ENC28J60 Ethernet Controller Datasheet (Version A)  
Microchip's ENC28J60 Ethernet Controller Datasheet (Version B - Latest)  
Microchip's ENC28J60 Silicon Errata Rev.B1  
Microchip's ENC28J60 Silicon Errata Rev.B4  
Microchip's ENC28J60 Silicon Errata Rev.B5  
Microchip's 25LC1024 Serial EEPROM Datasheet  
Microchip's 25LC256 Serial EEPROM Datasheet  

Useful Links

TCP/IP Stack Source code and useful software tools

Microchip's TCP/IP Stack v3.02  
Microchip's TCP/IP Stack v3.60  
Microchip's TCP/IP Stack v3.75  
Microchip's TCP/IP Stack v4.02  
Microchip's TCP/IP Latest Version  
Microchip's MPLAB Integrated Development Environment  
Microchip's MPLAB C18 Compiler  
Wireshark (formerly Ethereal) Network Protocol Analyzer  
CoffeCup HTML Editor 2007  

Additional Resources

Brush Electronics Ethernet Boot Loader  
Microchip TCP/IP Stack Application Note (AN833)  
Microchip Users Forum - TCP/IP-Ethernet  

    ©2006-2009, Jorge Amodio, All rights reserved

Last Update: Jan 28, 2008