Deep Dive

So, you want to go deeper into the tech behind the OnePSG. On this page, we assume you’ve already read the Intermediate Dive.

Physical:

Mechanical:

  • Other than the actual pedals and levers, the only mechanical parts on the OnePSG are the mechanisms that convert pedal and lever movement into sensor readings. After quite a lot design effort and tweaking, we have a small assembly with only three moving parts.

  • One moving part takes the pedal’s very small travel into the larger travel (about 1/2”) required by the Hall Effect sensor (see more under the Electronic section below) in order to get enough resolution needed by the Control MCU.

  • Attached to the above moving part is a magnet holder that moves when a pedal or lever is engaged. The Hall Effect sensor chip housed in the same assembly senses the changing magnetic field and sends a varying voltage to the Control PCB.

Electronic:

  • Control PCB:

    • In terms of electronic design, the Control (aka Main) PCB (printed circuit board) is a high-tech work of art. Being capable of simultaneously handling a variety of analog and digital signals and analog and digital audio all on one PCB makes the OnePSG possible. The board …

    • accepts inputs from pedal and lever sensors read from the Pedal/lever PCBs (see below).

    • accepts processed audio from the codecs.

    • houses one main microcontroller (MCU) and several digital signal processing (DSP) MCUs.

  • Main MCU: The main MCU is an STM32H7 microcontroller. This has many jobs;

    • Takes input from the touchscreen and displays information for the player.

    • Handles any USB tasks; e.g. firmware upgrades, sharing copedents saved on a USB drive, outputting separate channels (one for each string) to another USB capable target (DAW, etc.)

  • DSP MCUs: There are six smaller STM32H7 microcontrollers on the Control PCB. ,,,

  • Pickups: There are ten or twelve single string magnetic pickups. Like any magnetic pickup, each pickup (one per string) captures the string’s vibration.

  • Codecs: The pickups’ signals are converted by codecs into digital audio signals which are then pitch-shifted in real-time by the DSP MCUs. After processing, the digital signal for each string is converted by the codec back to an analog signal for final output to a guitar amp, for example.

  • Pedal/lever PCBs: There are ten small PCBs, one for each pedal and lever to capture the pedal or lever movement.

Software:

  • There are two main types of software running on the board. The DSP MCUs run signal processing code along with handling communication with the Control MCU.

  • The Control MCU’s code handles a number of different tasks:

    • Accept values from the pedal and lever sensors

    • Use those values to calculate how much each string’s pitch should change.

    • Communicate with the DSP MCUs: tell them what to do with the string signals and, in the case of tuning, receive the physical pitch of the string to display to the player (like any electronic tuner).

    • Handle stored data; e.g., saved copedents, saved tone profiles, etc.

    • User Interface (see below)

  • The DSP MCUs code takes the digitized audio signals from the codecs and pitch-shifts them based on the communication from the Main MCU.User Interface: