Build a MESA/Boogie BigFoot emulator

Bigfoot is a foot controller used for Dual & Triple Rectifier Head. It uses a non-standard and undocumented interface exposed on 8 pin DIN 270° connector so we need to reverse enginner it.

By disassembling it we can found the name of the pins printed on top of the PCB. After that, with a multimeter, we can observe the signal on that pins.

  • PIN 1 is the GND
  • PIN 2 is the Vcc 5V
  • PIN 8 is disconnected
  • PIN 6, called CH0 is unknown
  • PIN 3 is called V-CH is the only one pin that controls the three channels of the Amps. V-CH at 0,7V meaning CH1 (Channel 1) selected, 1,25V meaning CH2, 1,90V meaning CH3
  • PIN 4 SWB- and PIN 7 SWB+ are connected together and it controls the FX bypass switch. 0V means FX bypass OFF, 5V means FX bypass ON
  • PIN 5 is called SWA and rules the SOLO switch. This pin is 0V when the SOLO gain is ON, and 5V when the SOLO is OFF

Now we can build a simple interface to emulate the pedal board:

Where you see “Arduino” you can use any board that provides some digital outputs. These are the truth tables:

SOLO GAIN
INPUT D4 OUTPUT LED MEANS
0 0 ON SOLO gain is ON
1 1 OFF SOLO gain is OFF
FX Bypass
INPUT D5 OUTPUT LED MEANS
0 0 OFF FX bypass is OFF, so FX chain is active
1 1 ON FX bypass is ON, so FX chain is disabled
CHANNEL SELECT
INPUT D2 INPUT D3 OUTPUT MEANS
1 1 1.90V Channel 3 is selected
1 0 1.25V Channel 2 is selected
0 1 0.70V Channel 1 is selected
0 0

If you want to build a fully working BigFoot MIDI emulator, I’ve developed an open source device based on Arduino: HappySwitch – Open Source MIDI Amp Controller

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