peanutnore / guitarduino

Software for running Arduino based guitar effects. Supports ATMega 168/328 based Arduinos using onboard ADC and resistor ladder DAC on PORTB. The schematic is included for the board used to develop these sketches.

guitarduino

Software for running Arduino based guitar effects. Free software licensed under GPL.

guitarduino-mode-switching is the main release intended to run on the matching hardware to take advantage of the mode switches and provide 16 different effect modes.

Supports ATMega 168/328 based Arduinos using onboard ADC and resistor ladder DAC on PORTB. The schematic is included for the board used to develop these sketches and can be viewed / edited in Eagle 6 or higher. This instructable offers a good explanation of the resistor ladder DAC used: http://www.instructables.com/id/Arduino-Audio-Output/ NOTE: In the instructable PORTD is used for an 8 bit DAC. Even with 1% resistors it's impossible to achieve an accurate 8 bit resistor ladder DAC. In this project PORTB is used, which offers 6 pins (the 2 highest bits are used for the clock crystal on the ATMega chip. It is possible to achieve good accuracy for a 6 bit R/2R resistor ladder DAC using common 5% resistors, and this project is going for simplicity wherever possible.

guitarduino's Issues

Update processing logic to bitwise operations to improve speed

-core and -crush have been updated to use bitwise operations to map the 10 bit input to the 6 bit output. Validated in -speed-test. Other modules still use the map() function. For maximum sampling rate complex functions should be avoided. If a low sampling rate is desired map() may be part of that but better methods should be found for frequency doubling, amplification, etc.

Include schematic as image

Might it be possible to include the schematic as an image, for those of us without access to Eagle? Thanks!

Low pass and high pass filter modes do not produce output

Issue present in guitarduino-mode-switching

The LPF and HPF modes do not currently work. Possible causes might include the processing of each sample taking too long to run at audio frequencies, rendering output inaudible. Try using serial debugging to determine if this is the case:

//in setup:
unsigned long startTime = 0;
unsigned long endTime = 0;
unsigned long duration = 0;

//in loop:
startTime = micros();
//loop code
endTime = micros();
duration = endTime - startTime;
Serial.print("Duration in uS: ");
Serial.println(duration);
Serial.println();
delay(500);