Audio spectrum analyzer without DSP processor

When dealing with signals, probably the best way is to leave the task for DSP processor as they are optimised to do DSP calculations like FFT, filtering and other digital signal manipulation. But not always a DSP processor is an only solution, especially if you want a low cost and non-critical performance application like an audio spectrum analyser. In this project, an ARM7 (LPC2138) microcontroller is used to do an FFT algorithm. The tricky part about FFT on such microcontrollers is dealing with complex numbers that are also real. The project description shows the whole process of how these problems are solved. Project is set up on ZL6ARM prototype board, which is equipped with all necessary peripherals like LCD, MAX232 converter. The program is developed for ARM-GCC compiler. An audio signal is sampled by LPC2138 internal ADC with the selected sampling frequency of 40 kHz. An FFT algorithm calculates the chunks of 256 samples and produces the spectrum graphs on the PC screen. This is a great project and nice tutorial to get into DSP world. [source] Continue reading

Dual Axis Level Sensor – The Perfect Application for Home or Industrial

Most of the time, we’re have been experiencing this awful situation before. Go figure, how many times you’ve tried to adjust something for level with a spanner, but you’re not able to see how you doing! Furthermore, things start to out of control, if you are handling a pool table that has four adjustable feet, which you can fiddling around with the spanner and trying to figure out what is the exact table level is! Yeah, the whole scene could turn into a really nasty and huge pain for the fixer… However, there’s better solution for the above matter. Let’s meet the Mr. Incredible, Dual-Axis Level Sensor (Oops, is it really a person?). Basically, the dual-axis level sensor is based on LPC2138 microcontroller. Even though the designation is quite simple and unattractive, but it provides exceptional convenience to the users! For your information, the sensor system is fully-designed around electrolytic tilt sensors, where is capable of providing precise positioning measurements in within a few seconds! The units form the basis for many other applications. The Dual-axis level sensor is including… Continue reading

LPC2294 based webbox project

ARM microcontrollers are great for running embedded linux. This project got some power as it uses 2MB SRAM, Philips LPC22xx processor that runs at 60MHz, SD/MMC card slot, NIC 10Mbit RTL8019 Ethernet chip. If you dare to recreate this project – here are Eagle files needed. Also you need to load uClinux in to RAM memory with bootloader and uClinux source code with proper MMC/SD and network card drivers. Once everything is set – you can run various linux based servers like http, smtp etc. and access them via your computer client programs like browsers, pop clients – you name it. Continue reading

Running uClinux on ARM microcontroller

ARM microcontrollers are 32 bit systems with high potential. It is enough power to run small operation systems like uClinux. The only limitation is that operations systems require much more program memory than internal chip memory can provide. Ulrich Radig used a NXP LPC2294 ARM7 microcontroller which carries 256K of internal Flash memory which is enough to place a boot-loader which loads uClinux kernel to SRAM.   It interesting how he solved low memory problem. SD card was split in to two partitions where one partition FAT16 was used to store kernel which has to be loaded to memory, second is Linux (ext2) partiion for custom use. To support this he has written a simple driver. When Linux is loaded, it is easy to run various custom programs like web servers, and so on. Continue reading

Simple flash card audio player

Moving along the Philips ARM Design Contest 2005 projects list there is another interesting project you may find interesting. Its a flash card audio player which plays lossless audio tracks directly from MMC flash card. Interesting thing is that player is controlled by car audio head-end unit.   The idea was to emulate a CD changer so the head-end could be adopted to communicate with player. Instead playing CD tracks player changes the tracks in subdirectories. Each subdirectory appears as different CD to head-end unit. Other commands like play, stop, next CD, next track are normally supported. Audio signal is converted do analog through external high speed stereo DAC. Signal is sent back ti head-end unit for amplification after when music reaches speakers. Nice project probably more for learning purposes rather than practical. Download files here. Continue reading

Sophisticated telephone answering machine

This project is developed by Bernard Debbasch and is a winner in Philips design contest 2005. it is really cool and flexible answering machine which allows many things including Media storage, internet access where messages can be sent in form of SMS or e-mails, interfacing to phone line, DSP routines. Answering machine(TAM-TAM) also supports multiuser interface where up to four users can have custom settings.   The whole machine is built around LPC2138 ARM7 RISC microcontroller. Project gives a good demonstration of DSP functions including FSK demodulation, voice playback and record, DTMF tone generation and detection. Concurrently there are also running IP stack and File system management tasks. And still, whole system gives good level of performance. Code blocks are written so that they may be easy reused in other projects. All project files are available for download. Continue reading