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Table of Contents
MIDI Keyboard
A 25 key Midi keyboard based on an Arduino (Atmega328P-PU). It has an small OLED Display, too.
MCP23017
I2C
I2C SDA SCL Arduino Uno A4 A5
Setting the Adress
To set the I2C address of the MCP23017 one has to connect A0, A1 and A2 to GND or to power.
GND = 0 and +5V = 1
A0 A1 A2 adresse 0 0 0 0x20 0 1 0 0 0x21 1 0 1 0 0x22 2 1 1 0 0x23 3 0 0 1 0x24 4 1 0 1 0x25 5 0 1 1 0x26 6 1 1 1 0x27 7
And in the code one has to put the address in the “begin” command:
mcp.begin(address);
Pulldown Resistor
Every botton is connected to +5V and at the pin to the MCP23017 it has a 10k pulldown resistor to ground.
IO Pin ----- Button ------- +5V
|
10k
|
GND
Library
Adafruit-MCP23017-Arduino-Library
Datasheet
MCP23017
OLED Display
Pins:
GND: power ground VCC: 3.3v or 5.0V power supply D0: ClK D1: MOSI data RST: Reset DC: Data/Command CS: Chip select Port
Bit Converter
http://en.radzio.dxp.pl/bitmap_converter/
Example Code
OLED-Example