Universal PIC 18F Board  

Table of contents

Purpose

Based on the experiences with the IPS Board I present here a design for a multi purpose prototyping board for PIC 18F's. Microchip offers a broad range of microcontrollers (PIC's) for various applications. If you use such microcontrollers to develop and prototype sollutions it can become cumbersome to design different prototyping boards over and over again depending on the controller used. Thats why I made the effort to design a Universal PIC Board UPB where a broad range of different controllers (mostly of the 18F series) can be used. The board offers RS232 (RX,TX including RTS,CTS), USB, a switch, a LED, ICSP, a reset and power monitoring, I2C, external/USB power, power stabilization, connector for alternate power (battery) and power switch and an expansion bus.

 

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Features

Some may ask now 'Why another microcontroller board?'. And there are more than one answer to this question:

  1. The presented board is capable to use different microcontroller types like the 18F458, 18F4550 or the 18F877 to name just a few. They all have nearly the same pin layout and also other types with comparable pinouts should work with this board.

  2. RS232 support (including RTS/CTS support) as well as USB (depending on the used controller) are available on the board.

  3. No usage of SMT parts. This makes it relatively easy to build the board yourself. Nevertheless are the board dimensions very small (10 cm x 5,3 cm which is only 1/3 Euro board).

  4. 5V power supply on the board can be realized using either a standard 78x05 linear regulator or some low drop regulator like the MAX603. External power source is either a wall plug or via USB.

  5. Power monitoring, reset and brown-out detection is done by a DS1813 IC

  6. One LED and one switch is available on the board for free usage.

  7. In circuit serial programming (ICSP) of the microcontroller is supported (if it supports it) via a 6 pin header. Using a DIL4 Dipswitch ICSP signals can be disconnected from the rest of the board while programming.

  8. Via a 40pin bus on the bottom of the board, add on boards can be stacked on top of the microcontroller board. 99% of the microcontrollers pins are available on this bus.

  9. By using a 40pin adapter board (see Pictures) the microcontroller board can be used in breadboard prototyping.

The etched board
The etched board		 The finished UPB
The finished UPB
Breadboard adapter
Breadboard adapter		 Adapter with board
Adapter with board

Schematics

The schematic for the UPB is a classical microcontroller design. Besides the power supply you will find the RS232 (suporting RTS/CTS) using the MAX232 (or a clone), a LED (connected to port B1), a switch (on port B0 which allows interrups), a crystal, a reset and monitoring IC (DS1813) and the USB port.

Power section schematic
Power section schematic
Digital section
Digital section

The PCB

There is nothing special to say about the PCB. This double sided PCB is just 10 cm x 5,3 cm in size and contains no SMT parts. The board can be customized bei using the jumpers J1-Jx or the copper jumpers Bx1-Bx11. Bx jumpers can be opened by using a sharp knife and closed by using a small solder bridge. The default board configuration is enabled RS232 including RTS/CTS, I2C, the switch and the LED. USB is disabled by default.

Please note that some jumper configurations can damage your board or microcontroller. PIC's share USB and I2C pins. So either you close Bx9-Bx10 and open Bx5-Bx6 ore vice versa. Also JP5 and JP6 are mutualy exclusive.

Complete board layout
Complete board layout

 

 Component layout
Component layout

 

You can download a PDF File with the schematic and the PCB here.
If you dont have the Adobe Acrobat Reader installed on your machine you can find it here
   
Jumper
JP1DIP-SWICSP VDD 
JP2DIP-SWICSP MCLR 
JP3DIP-SWICSP Port B7 
JP4DIP-SWICSP Port B6 
JP5Jumperuse USB power 
JP6Jumperuse external power 
Bx1SMTRS232 CTS on Port C1closed
Bx2SMTRS232 RTS on Port C2closed
Bx3SMTRS232 RX on Port C7closed
Bx4SMTRS232 TX on Port C6closed
Bx5SMTI2C SCL PullUp R2 on VDDclosed
Bx6SMTI2C SDA PullUp R3 on VDDclosed
Bx7SMTSwitch SW1 on Port B0closed
Bx8SMTLED D3 on Port B1closed
Bx9SMTUSB D- on C5open
Bx10SMTUSB D+ on Port C4open
Bx11SMTUSB PullUp R4 on Port C32open
 
Connectors
PWR1Barrelexternal power supply
PWR22Pin JumperInternal power supply (battery). Disconnected by switch on PWR1 if external power used
PSW2Pin JumperConnector for On/Off switch
RS232RJ45Serial interface (DTE). To connect to a PC use a 1:1 streight cable from RJ45 to SUB-D9.
USBUSB-BUSB Connector
ICSP5 pin SIPIn Circuit Serial Programmin connector (ICSP)

  1. GND
  2. VDD
  3. MCLR
  4. Port B6
  5. Port B7
BUS40 pin headerexpansion bus

  1. GND
  2. VDD
  3. A1
  4. A0
  5. A3
  6. A2
  7. A5
  8. A4
  9. E1
  10. E0
  11. N/C
  12. E2
  13. C1 - RS232 CTS
  14. C0
  15. C3 - I2C SCL
  16. C2 - RS232 RTS
  17. C5
  18. C4 - I2C SDA
  19. C7 - RS232 RX
  20. C6 - RS232 TX
  21. D1
  22. D0
  23. D3
  24. D2
  25. D5
  26. D4
  27. D7
  28. D6
  29. B7
  30. B6
  31. B5
  32. B4
  33. B3
  34. B2
  35. B1
  36. B0
  37. N/C
  38. N/C
  39. C4 - I2C SDA
  40. C3 - I2C SCL

Notes & Comments

in the Press

This paper can also be found in the german HAM Radio Magazine
"Funkamateur" at www.funkamateur.de, Issue 07 / 2007, Page 748,
Title: "Universelles PIC-Board als Grundlage für SSTV-Modul"

Credits

If you have any comments or sugestions just drop me a line.

73, OE1RIB