There are several compilations options that can be set when compiling o_C firmware yourself. These options can be enabled by editing the OC_options.h file, which by default should look something like this:

 * compile options.

#ifndef OC_OPTIONS_H_
#define OC_OPTIONS_H_

/* ------------ uncomment for eurorack Buchla support: ----------------------------------------------  */
/* ------------ uncomment for use with Northernlight 4U version: ------------------------------------  */
//#define BUCHLA_4U
/* ------------ uncomment for boring app names ------------------------------------------------------  */
/* ------------ print debug messages to USB serial --------------------------------------------------  */
//#define PRINT_DEBUG
/* ------------ flip screen / IO mapping ------------------------------------------------------------  */
//#define FLIP_180

Enable each option by removing the comment marking from in front of the releavent line, save the file, and recompile and upload.

Thus, to enable this option:


change the line to read as follows (and save the file before recompiling and re-uploading to the module):


The options


Enabling this adds two more output voltage scaling options to permit eurorack O_C modules to drive 1.2V/octave or 2V/octave Buchla modules. The output scaling is accessed in the same way that it is for the non-octaval scales, on a per channel basis - see the section on “Non-octaval tunings for the xenharmonically obsessed” in the manual for details. 1.2V/octave and 2V/octave output scalings appear below the non-octaval output scalings when this option is enabled.


Some Buchla modules, particularly those containing microprocessors or other digital circuitry, are (somewhat remarkably) NOT tolerant of negative voltages applied to some CV inputs. O_C, like almost all eurorack modules, is capable of outputing negative voltages, and thus may damage such digital Buchla modules if used incorrectly. Please only use the eurorack version of O_C with Buchla modues or devices if you know what you are doing, and understand that you do so at your own risk.


This option is for use with the Northern Lights dual O_C module for 4U Buchla systems. These modules provide 0 to 10V outputs only, and are therefore always safe to use with digital Buchla modules. See


Enabling this changes the incredibly witty, punning app names to a set of boring descriptions, as follows:

  • CopierMaschine becomes ASR
  • Harrington 1200 becomes Triads
  • Automatonnetz becomes Vectors
  • Quantermain becomes 4x Quantizer
  • Meta-Q becomes 2x Quantizer
  • Quadraturia becomes Quadrature LFO
  • Low-rents becomes Lorenz
  • Piqued becomes 4x EG
  • Sequins becomes 2x Sequencer
  • Dialectic Ping-Pong becomes Balls
  • Viznutcracker, sweet! becomes Bytebeats
  • Acid Curds becomes Chords
  • References becomes Voltages

This enables various debug functions useful to developers, including printing of storage information to the Arduino IDE serial device.


This flips the module upside-down. The display is flipped top-to-bottom and left-to-right, the buttons are transposed top-to-botoom, and the inputs are appropriately transposed left-to-right, and the outputs transposed both left-to-right and top-to-bottom, thus:


This is useful, for example, if you wish to mount the module in the lower row of a performance rack. Suitable panels may be available from Oscillosaurus.