Homebuilt Hardware

Digital Noise

Posted in Synth DIY by admin on the April 4th, 2007

Over the last few days, I have been thinking about a digital noise circuit. The CD4006 (18-bit shift register) is commonly used but it is becoming difficult to find. Instead, I have written assembly code for a 32bit Linear Feedback Shift Register (LFSR). This code is programmed in an ATTiny13 8bit AVR microcontroller. The tiny13 runs with an internal clock of 4.8MHz. I have coded two versions; the first runs in self-clocked mode with a 192KHz shift rate and the second uses an external interrupt for the shift clock and this one supports up to 145KHz shift rate (290KHz with a 9.8MHz cpu clock). These two designs offer a low parts count and small footprint noise source. I’ll be updating the project page here after I have tested these and some more ideas.