Sunday, April 12, 2015

USB Controlled 8x40 Dot Matrix Moving Display Circuit - 18F2550


2015-04-12 Initial release
2015-04-16 Wrong Configuration Bits - Fixed

This dot matrix moving display message board will be of five, 8x8 dot matrix, which will be able to display 10 different messages and maximum 60 characters of each. You can set messages by using PC application that created by me using visual basic and those messages will show on matrix display. When the circuit is disconnected form PC then default messages displayed on the display.

USB Controlled 8x40 Dot Matrix Moving Display circuit
Circuit Diagram

PIC18F2550 is the micro-controller and main part of this circuit. This IC used because it has built-in USB transceiver that used to communicate with PC application. PORTB of IC controls the row of Matrices. This PORTB pins then connected to display through the ULN2803 IC, which consists of 8 Darlington arrays. Because micro-controller unable to handle heavy load. In the diagram, you can see 8 NOT gates. These gates used only simulation in Proteus. Therefore, you should replace with these gates with ULN2803 IC. The columns are driven by the outputs of a 40-bit serial-in-parallel-out arrangement constructed by cascading five 74HC595 ICs. The 74HC595 device is an 8-bit serial-input and parallel/serial output shift register. The serial output feature allows cascading of multiple 74HC595 devices. The time format of PC must be in English, otherwise time will not display properly on the display. LED is indicated that whether USB cable connected or not and Scrolling speed of circuit can be change by varying the value of VR1. Supply voltage for this circuit is 5v.

The PC application and other files can be download from below link.

Friday, April 3, 2015

USB HID Bootloader Circuit - 18F4550



If you are use mikroC PRO, then tick the Long Hex format in output settings and rename the generated hex file to scp.hex. Finally run mod.exe. It will generate new hex file (mod.hex) and use it with PICDEM software. Otherwise, program may not work correctly.

Boot-loader is a program which helps to program the micro-controller device without using external programmer. It is possible to burn the hex code even if the PC doesn't have a serial port or any other tools.

Required tools for Boot-loader are:
  • USB cable to connect board to the PC
  • A micro controller with already flashed boot loader program

USB HID Bootloader circuit
Boot-loader circuit

The boot-loader starts after Power-On or Reset. The boot-loader checks if pin RE3 is low or high:
  • RE3 = low (0V) : PIC starts in boot-loader mode
  • RE0 = high (5V) : PIC starts user application

Install Boot-loader program

For installing boot-loader program, we need an external programmer. This is a one time process which doesn't need to repeat. Use any programmer like JDM, PicKit, ICD3 to flash the provided boot-loader program USB HID Bootloader.hex.

After successfully programming, connect your device to the PC's USB port (if not already connected). Please make sure that the boot-loader entry condition (RE3 = 0) is fulfilled!

Windows should detect a new USB device. Now open boot-loader PC software and click connect, browse hex file, begin upload.

After finishing upload device will reset automatically and start your program.


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