Interfacing an Analog-to-Digital Converter (ADC) with Linux via the parallel port is fairly simple. There two major areas that need to be addressed - hardware and software. The hardware consists of the parallel port, an ADC, and an analog signal source. The software we programmed in ‘C’ language.
Interfacing Your Computer to an ADC via the Parallel Port: [Link]
This project is a simple 12-bit, 8-channel analog to digital converter (with 4 additional digital inputs), which may be connected to the PC through the serial interface (RS232). The sequence of sampled channels, and sampling frequence are programmed by the PC while the maximal sampling frequency is limited by the data transmission rate, and at 115200 baud is equal to ca. 3kHz for 1 channel without digital inputs, and to ca. 500 Hz for 8 channel with digital inputs.
The analog input voltage range is -2.5V to 2.5V. The digital inputs may be used for recording additional digital signals, eg. the time code used to synchronize the recorded data with other events. The project is based on PIC16F84 (or 166C84) microcontroller, and MAX190 (or MAX191) ADC. The device is mounted on a small single-sided printed circuit board, easy to prepare even at home.
PIC16F84 12-bit, 8-channel analog to digital converter: [Link]
This is great project demonstrating an organic LED display interface. ARM7 (AT91SAM7S64) microcontroller displays and analog clock face on OLED screen which has 18 bit color range and is low power. Project uses DS3234S RTC IC that is interfaced to ARM7 microcontroller via SPI port. Another interesting feature is that clock uses a light sensor TSL256 which enables to adjust displays brightness according to ambient light level. So in dark environment clock is dimmed while in bright room brightness is high. OLED allows 16 brightness levels.
The Squarecave is a hybrid digital and analog music synthesizer. It uses digital CMOS ICs to generate a sequence of oscillations of varying pitch and volume, and then pipes the result through analog filters (lo-pass, hi-pass, band-pass).
Squarecave: DIY analog/digital synthesizer: [Link]
