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Author Topic: Newbie Analog Guitar Pedal Storing and Loading Presets HELP  (Read 714 times)
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HI,

I am relatively new to Arduino and need to know if the project I intend to build will be feasible:

I apologise if I've posted this in the wrong space.

I have built a few analog distortion guitar pedals, big muff e.t.c and wish to build my own that will be able to save presets (Potentiometer values/Switches) and store them in the Arduino in order to be recalled and loaded onto the pedal with some buttons and make the change to the sound.

My objective is to get an analog pedal with digital control and ability to store presets.

The main issue I have is How the sound will be changed as I want the effect to come from the analog electronics(transistors/diodes e.t.c) and NOT from programming it.

I believe that I can store the values from something like a digital potentiometer connected up to the electronics which sends the values to the Arduino and later are coded into memory but am unsure on how to Overwrite the current settings and change the sound.

I understand this would be easier making it pure digital but I want to keep the analog sound.

Feel free to ask any further questions as I may not have explained this that well and also suggestions of simpler ways of achieving this are welcome

Thanks

James
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you can store values in the EEPROM of the Arduino.

You can control this with a switch that loads the next setting from EEPROM. 
you can add a display to show the memory slot.   

so 3 switches in the end
1) select EEPROM slot
2) load settings from EEPROM and make them current
3) save current settings to selected EEPROM slot.

with the current settings you can control a number of IO lines e.g. for DAC (digital to Analog COnvertor) that controls your analog soundmachine.

my 2 cents,
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Thanks for the reply, that doesn't seem too difficult. Perhaps you could give an indication of how it might wire up to the Arduino?

So that's great being in control of the IO lines but to start with I would only be using  1 output(jack) and 1 input(jack) so i'm assuming I could use 1 cable from one of the OUT sockets(Would that be Digital out?) and am unsure where it would attach to my circuit.

I'm confused as to how to make the change of value of the potentiometer to the sound (sent to output jack) without actually turning the potentiometer and purely by loading the value from the EEPROM memory onto my circuit e.g. where is the stored value taken? Perhaps this needs an onboard chip then connected to my circuit or a different component.

Thank you for the feedback so far, It's very important I get the processes right.

James



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for switches you can use e.g. solid state relays
and digital potentiometers connect to I2C bus.  (fast enough)

how many switches and how many potmeters you need to connect?
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There will be many switches and potentiometers, around 4 switches, 8 potentiometers.

Are there limits of how many can be connected to the I2c bus? Would this mean multiple arduino's or one with more pins.

All of the controls ideally will need to be saved in the EEPROM memory.

Thanks again,

James
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The I2C bus can connect up to 127 devices and with some tricks even more. However every I2C device has an address and some can be tweaked by hardware  address lines and that gives a max number of a certain type of device that can be on an I2C bus.

e.g. device A  has 3 configurable address lines => 8 possible addresses => max 8 devices.

The EEPROM of an UNO is 512 bytes 
4 switches ON/OFF can be in one byte
8 potmeters  2 bytes per pot?
=> 17 bytes for all.

512/ 17 => 31  presets

should get you started, otherwise add an I2C EEPROM of 32 KB ( I2C EEPROM 24LC256 )
32KB / 17 ~~ 1900 presets
- http://playground.arduino.cc/Main/LibraryForI2CEEPROM -

probably you want give the presets  a name or so
4 switches ON/OFF can be in one byte
8 potmeters  2 bytes per pot?
string of 14 chars
total 32 bytes   ==> 1000 presets

Only thing missing is some hardware and code ....

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for the potmeters you could read this: - http://arduino.cc/en/Tutorial/DigitalPotentiometer -

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for switches you could use something like these - http://www.natalnet.br/~aroca/afron/CD4066BC.pdf -
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