linear feedback shift register pin sequence

This is about the frame rate of old motion picture films. It should be noted that in order see the on/off contrast of the switching LEDs, the rate of switching must be less than about 25 per second (40 msec period). The circuit is shown in Figure 2.įigure 2. This signal is enough to trip the MCU analog comparator inputs AIN0,AIN1. The voltage gain of the amplifier is 2x, so it really behaves more as an impedance transformer. Here, the microphone output is capacitively coupled to an LM358 operational amplifier.

For aesthetic reasons, I needed something much simpler and using minimum through-hole components. There exist fine (and cheap) microphone amplifier modules that produce nice analog waveforms (e.g., based on MAX4466). Microphone InterfaceĪn Electret microphone is very sensitive but its output signal needs amplification. The top silk screen layer outlines the tree profile. The Christmas tree printed circuit board is a four-layer board developed using ExpressPCB Classic free CAD tools.

The Arduino Uno ATmega328P MCU is certainly capable of driving 16 LEDs and interfacing with a microphone.Īn Arduino Uno and a breadboard was everything required to develop this standalone ATmega328P project. Total cost is $40-60 each depending on quantity.Īrduino provides a low-cost development environment that I have used before. Socketed integrated circuits enable firmware updates for user customization. All through-hole component technology makes for easy assembly.If no sound is detected for 30 seconds, all the LEDs turn off and the tree enters a low-power stealth mode, fading discreetly into the background but poised to respond to the next sonic vibration.This produces a pleasing, eye-catching pattern as the bits shift in order around the 16 LEDs. A 16-bit Linear Feedback Shift Register (LFSR) creates a maximal length Pseudo Random Bit Stream (PRBS) dynamic LED sequence.An Electret microphone connects to the MCU analog comparator pins (AIN0/AIN1) to detect sound which animates the LEDs.The unit is powered by a 6 VDC, 600 mA AC adapter (wall wart). General DescriptionĪs shown in Figure 1, the LED Christmas Tree consists of a green printed circuit board in the outline shape of a tree decorated with 16 LEDs.Ī microphone responds to ambient sound to effectively clock a microcontroller (MCU) executing different LED sequence patterns. I’ve built LED Christmas trees before from kits and original designs as Christmas gifts for my relatives and friends. Christmas season is my favorite time of year.

Linear feedback shift register pin sequence