Dilshan R Jayakody’s Web Log

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 an AT89S2051 base 8bit bus monitoring utility. This module indicates bus values using hexadecimal numbering format and notify value changes by the beep. This utility is design to work with any 5V compatible TTL/CMOS - data/address buses. This 8bit bus monitor requires 5V external power supply. In the idle mode this unit draws 15mA of current and in working mode (when inputs get change) this may raise up to 20mA – 30mA. Due to this low power profile, this system can also attach into the PSU of the "testing system". This module is release as an open hardware project and it is covered with Creative Commons Attribution-ShareAlike 3.0 license . All the project related resources are available at Open Hardware Hub .

Kidogo is 8 channel USB self powered digital signal injector. Kidogo system consists with Signal Editor and USB interface module. Kidogo Player is the Signal Editor of the Kidogo system and it can support up to 512 time slots (each range between 1ms to 1s) with 8 channels. USB interface of the Kidogo system is based around Microchip’s PIC18F2550 microcontroller and generate 5V CMOS and TTL compatible outputs. Dimensions of current version of Kidogo USB interface is 53mm x 40mm (using standard through-hole components) and this can be reduce into more by using PCB layout based on SMD components. Kidogo Player is design to work under the Microsoft Windows operating systems and it has following general features: Save waveforms and settings as binary file (KDF file) or export waveform as a text file Playback controls such as “Play to segment”, “Play from segment”, “Step back”, “Step next” and “Clear” Shifting and rotating waveforms Invert, Reset, Clocking and Binary Generator functions Cop...

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.

This is a Microscopic view of Fairchild Semiconductor's MBM27C64 E 2 PROM IC and ST Microelectronics M27C512 E 2 PROM IC. M27C512 MBM27C64

This post show completed view of digitally controlled audio power amplifier with virtual surround (which we described in previous post). All the speaker enclosures, power amplifier casing and electronic system are design and developed by us. Configuration of this given step is as follows: System Components: Power Amplifier, 2 main speaker units, 1 sub-woofer and 18V (5A) SMPS. Speaker System: Main speaker system consist with 8Ω (45W) 6½ inch Woofer, 8Ω (50W) 3 inch Tweeter with passive crossover. Subwoofer System: 3Ω (200W) 8 inch Bass Woofer. All the speaker enclosures are mad out of 9mm MDF (medium density fiberboards) and power amplifier casing is made using 2mm acrylic sheets. More views of this audio system are available in here .

In this post we describe digitally controlled 2.1 channel audio power amplifier with virtual surround sound. This audio amplifier is based around Microchip’s PIC18F452 microcontroller and ST microelectronics TDA2050 power amplifiers. Key system specifications and features of this audio system are listed in below: Supply voltage and PSU: D.C - 16V to 19.5V with 3A PSU. (Recommended: 18.8V, 3A PSU) Input(s): 2 analog input lines. (for Left and Right channels) Functions: Volume, Bass, Treble, Loudness, Mega Bass, Surround Effects Volume control: 0dB to 75dB Attenuation per channel with 1.25dB step Mute: 100dB Attenuation per channel Calculated channel separation (Approximately): 85dB - 88dB Bass control: ±14dB with 2dB step Mega bass control: 0dB to 30dB with 7 control steps Treble control: ±14dB with 2dB step Surround Sound: Based on AViSS 3D surround algorithm with 4 operational modes (Disable, Low, Normal and Wide) Output channels: 3 (2 channels + 1 subwoofer driver channel) Output po...