Dilshan R Jayakody’s Web Log

CoCA "Emerge + Tech" - Musical plants is an electronics, software and plants base exhibit we developed for Cinnamon Colomboscope 2016 exhibition. This installation will feature a touch-sensitive sensor that will generate a soothing sound from each plant. By interacting with individual plants, the audience can create musical compositions. The sensor unit of this project consists of 14 high sensitive, configurable level detectors and USB interface. In this sensor unit, we use Samsung's KA2284 as an amplifier, level detector, and PIC18F4550 8-bit MCU as data multiplexer and USB I/O controller. PC817 optoisolators are used to interface between analog front-end and digital data processor. In this design, both analog and digital circuits are physically and electronically isolated to minimize the noises and interferences. In this design, we use KA2284 because it is commonly available in the local market (in Sri Lanka) and costs less than 0.1 USD. To reduce the interfer...

Curve tracer is an electronic test instrument to analyze the characteristics of transistors and other discrete semiconductors. In this post we construct USB base curve tracer to analyze properties of NPN transistors. This curve tracer is build around Microchip's PIC18F4550 MCU and it use simple Windows based GUI application to plot captured data of a transistor. In this design PIC18F4550 MCU is used to establish USB connectivity, perform voltage readings and control current/voltage flow into the test subject. To minimize the cost and to make it simple, we use R2R ladder circuit to generate discrete collector-emitter voltage levels for the transistor on test. In each scan session collector-emitter voltage level get increase from 0V to 7.5V in 256 steps. In this design, "tracer" scans the transistor for 7 base current levels which are in between 7µA to 60µA. In viewer application collector-emitter voltage levels are plotted on x-axis and collector current is plotted o...

When it comes to AVR microcontrollers the most common programming option is In-System Programming ( ISP ). ISP interface is easy to use but in some scenarios it is totally unusable. The most common scenario is with some wrong fuse bit values. For example if we program SPIEN or RSTDISBL fuse bits, AVR microcontrollers may not respond to any in-system programmer(s). To overcome these problems the next available option is high voltage programming mode. In High voltage programming mode, 12V programming voltage is applied to RESET pin of target AVR microcontroller and user can change configuration fuses of AVR MCU with minimum amount of risk. The only drawback in this mode is that target microcontroller must need to be removed from the board to reprogram. Most of the AVR high voltage programmers are expensive and difficult to find in ordinary electronic shops. As a solution we implement USB base high voltage parallel programmer for AVR microcontrollers and it allows programming, readi...

Virtually all PIC microcontrollers have some banking mechanism to extend addressing to additional memory space. But this external data memory is not directly addressable (except in some high versions of PIC18 devices, which include PIC18F8520, PIC18F6620, etc.). In this post we describe easy to implement external memory interface for PIC microcontrollers. Theoretically most of the PIC microcontrollers can use this setup to extend its RAM space. At the prototyping stage we test this system with PIC16F877, PIC16F887, PIC18F4550 and PIC18F4620 microcontrollers. With current setup user may be able to address RAM space up to 192KB. But this can be extended up to 448KB by adding more SRAM modules to the system. In this given schematic we use W24512 – 64K x 8 CMOS SRAMs as a memory modules. 74HC373 latch is used as 8bit to 16bit address extender and 74HC138 demultiplexer is used as memory bank selector. All the files (including source codes, EAGLE schematic files, etc.) of this syste...

This is another configurable PIC microcontroller development board with E 2 PROM base storage and RS232 interface. Purpose of this development board is to emulate simple computation platform with storage, processing unit and control terminal. This development board contain LM2576-ADJ base 3A switching voltage regulator (with external power terminals), E 2 PROM base storage (AT24C04) with 512words × 8bit space and standard RS232 serial interface. All the peripherals of this development board can be isolated using onboard jumpers which include crystal oscillator, MCU reset line, E 2 PROM I 2 C interface and UART interface. This development board supports most of the 40pin 5V PIC microcontrollers which include PIC18F4550, PIC18F452, PIC18F4620, PIC16F877, PIC16F887, etc. Schematic diagram of this development board is available in Circuitbee with Creative Commons Attribution-ShareAlike 3.0 license.

In this project we develop easy to build Microchip PIC development board for widerange of PIC Microcontrollers (which include 40pin Microchip PIC16 and PIC18 devices). This development board contain only the switching regulator (to generate +5V DC from the input power source) and RS232 serial port interface. The switching regulator of this development board may support input voltage of +8V to +25V DC. RS232 Serial interface of this development board is based on Maxim's MAX232 driver/receiver IC. This given design have 6 two-way jumpers to select crytal osciliator, MCLR and RS232 Tx/Rx terminals. While at the protyping stages we test this board successfully with PIC16F887, PIC16F877/A, PIC18F452, PIC18F4550 and PIC18F4620 MCUs. Diamensions of this PIC Development Board is 110×85mm. Schematic, PCB design and some of the related documents of this project are available to download at google drive .

In this project we develop USB port base controller for XBMC application. Main functionality of this controller unit is to provide remote control interface, LCD base - player information panel and rotary encoder base controller for XBMC. With this given hardware design and software programs, user may be able to control XBMC without using standard input devices such as keyboard and mouse. This device is design to work with XBMC Version 10.1 ( codename Dharma ) or newer versions. Older version of XBMC may not work this system because of the differences in its Web Control Interface. PIC18F4550 is a main hardware controller of this system. This microcontroller is used for USB interfacing, as LCD driver, IR base remote control data decoder and as a driver of the other input devices (such as rotary encoder and push switches). Controller’s USB interface is design to work as USB HID class device. This system is design to work with Microsoft Windows Operating Systems and we test this...