I.9. Recommended Development-Mode Pedal Wiring

Figure 1. Blackstomp’s Hardware Circuit Schematic Diagram
Figure 6. Recommended Wiring for Development Mode Pedal

The recommended wiring for development-mode pedal is shown in the Figure 6. The schematic diagram shows the wiring of the off-board components. Here is the bill of (off-board) materials:

NUMPART NAMEQTY.Connection ReferenceConnection Description
1DC socket for 9V DC input.1H7.1DC input
2SPST (normally open, momentary) foot switch2H13.2, X2.4Main and aux button
3Red LED3R(1K), H16.2, H17.2,Power, main, and aux LED indicators.
41K Resistor2VD33, H2.2Power LED and control port current limiter
5330R Resistor1VD33/H6.3EXP.P/CV 3.3V source current limitter
6SPDT ON-ON toggle switch2H14, H7.2PROG/RUN switch and ON/OFF switch
7DPDT ON-OFF-ON toggle switch1J1UART/MIDI switcher.
8TS socket 6.3 mm4H9, H10, H11, H12L/R inputs and outputs
9TRS socket 6.3 mm1R(1K), R(330), POTEXP.P/CV IN.
10TRS socket 3.5 mm7H8, H18, H19, J1, X1, VD33, X2MIC, MIDI, UART, I2C, DC OUT, ENC. IN
11Potentiometer B10K6H1, H2, H3, H4, H5, H6Control Knobs

Power-ON LED indicator is very important for development-mode pedal, while it’s not needed for most end products. In an end-product, we can always use the main LED as the CHECK indicator to see if the effect is engaged or not. In contrast, we need a more reliable power indicator to make sure if the power supply is indeed working while debugging the algorithm, including the part that operate the LED indicator.

CTRL 2 potentiometer share the function of analog expression pedal or control voltage (CV) input (CTRL 2/EXP.P/CV). If a TRS jack is plugged into the EXP.P/CV IN socket then the TRS connector will takeover the CTRL 2 potentiometer connection.

Encoder input port. For the most accessible and available part, the port is implemented as 3.5 mm TRS socket and it has only 3 channels and it accommodates only the GND (X2.1), X2.2, and X2.3. The X2.4 input (for the rotary click button) is available on 3.3V port at RING channel, but keep in mind that this input is shared (in parallel) with the second foot switch (the aux button).

PROG/RUN toggle switch determine if the system should run the bootloader (firmware programmer/loader) or run the already programmed firmware when the system starts (after power-on or after reset). At PROG position, every time the power is turned-on or the reset button is pressed then a bootloader program will be started. Starting a bootloader program means that the system will be waiting a stream of firmware’s binary stream on UART port (sent by a PC that runs a flash programmer application) to program the flash storage with new firmware codes. At RUN position, the pedal will run the effect as in normal usage. Switching the PROG/RUN into any position while the pedal is already running has no effect until the pedal restarts.

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