KnobGPIO

Plugin for the ChucK programming language.

Prerequisite

MCP3008

The MCP3008 is a 10-bit Analog-to-Digital Converter (ADC) chip that allows microcontrollers (like the Raspberry Pi) to read analog signals. The Raspberry Pi does not have built-in analog input pins, so if you're using an analog sensor (like a potentiometer, temperature sensor, or light sensor), you need an external ADC like the MCP3008 to convert the analog signal into a digital value that the Pi can process.

MCP3008 Pin	Connect to Raspberry Pi Pin
VDD (16)	3.3V (Pin 1)
VREF (15)	3.3V (Pin 1)
AGND (14)	GND (Pin 6)
CLK (13)	GPIO11 (SPI CLK, Pin 23)
DOUT (12)	GPIO9 (SPI MISO, Pin 21)
DIN (11)	GPIO10 (SPI MOSI, Pin 19)
CS (10)	GPIO8 (SPI CE0, Pin 24)
DGND (9)	GND (Pin 6)
CH0 - CH7	Connect to potentiometer middle pin or other analog sensor

       _______
CH0 --|1  ° 16|-- VDD     -> 3.3v
CH1 --|2    15|-- VREF    -> 3.3v
CH2 --|3    14|-- AGND    -> gnd
CH3 --|4    13|-- CLK     -> GPIO11 (SPI CLK, Pin 23)
CH4 --|5    12|-- DOUT    -> GPIO9 (SPI MISO, Pin 21)
CH5 --|6    11|-- DIN     -> GPIO10 (SPI MISO, Pin 19)
CH6 --|7    10|-- CS/SHDN -> GPIO8 (SPI CE0, Pin 24)
CH7 --|8_____9|-- DGND    -> gnd

Install

On linux

git clone https://github.com/pierreportal/KnobGPIO.git

cd KnobGPIO

make linux

sudo make install

Usage

Basic Usage

KnobGPIO knob;

while (true)
{
    <<< knob.last() >>>;
}

Advanced Usage

KnobGPIO knob;

// Set ADC channel (0-7, automatically clamped if out of range)
knob.setChannel(0);

// Optional: Adjust update rate for performance tuning
// Default is 441 frames (~100Hz at 44.1kHz sample rate)
// Lower values = more responsive, higher CPU usage
// Higher values = less CPU usage, slower response
knob.setUpdateRate(220);  // ~200Hz update rate

while (true)
{
    <<< knob.last() >>>;
}

Features

• Channel Validation: Channels are automatically clamped to valid range (0-7)
• Error Handling: Graceful fallback if GPIO/SPI initialization fails
• Performance Optimization: ADC reads are throttled to reduce CPU usage while maintaining responsiveness
• Robust Operation: Continues outputting last valid value if ADC read errors occur