hexeguitar / encoderboard

Rotary encoder board + I2C driven 16xLED ring

Rotary encoder board / I2C driven LED ring

Mounting board for the Panasonic EVEP series rotary encoders equipped with I2C driven 16 LED ring.

LED driver is built around the MCP32017 16bit I2C IO expander. Up to 8 modules can be used on the same I2C bus. Compatible with 5V and 3.3V supply voltage.

MCP23017 I2C slave address

The values shown on the schematis are 8 bit wide and intended to use when you write your own I2C subroutines, like:

...
I2C_Write(DEVICE_ID | WRITE_BIT);
...

To use them within popular I2C libraries, like the Arduino/Wire divide the address by two/right shift it 1 bit. For A0,A1,A2=0 it will be 0x20 instead of 0x40.

LED ring control

First we need to set the both ports A and B to outputs, as the default setting is input. The procedure is very simple:

I2C_Start();					                      //generate start condition
I2C_Write(MCP23017_SLAVE_ADDR | WRITE_BIT);	//send slave address and set the write bit(0)
I2C_Write(0x00);				                    //write to address 0x00=IODIRA
I2C_Write(0x00);				                    //set all A pins to output, write is sequential, address pointer ++ = IODIRB
I2C_Write(0x00);				                    //set all B pins to output
I2C_Stop();					                        //generate stop condition

Updating the LEDs, thanks to the sequential write is also trivial:

void UpdateLeds(uint16_t value)
{
  I2C_Start();					                      //generate start condition
  I2C_Write(MCP23017_SLAVE_ADDR | WRITE_BIT);	//send slave address and set the write bit(0)
  I2C_Write(0x12);				                    //write to address 0x12=GPIOAA
  I2C_Write(value&0xFF);				              //write lower 8 bits to PORTA
  I2C_Write(value>>8);				                //write higher 8 bits to PORTB
  I2C_Stop();					                        //generate stop condition
}

On platforms as Arduino you can use the Adafruit MCP23017 Library

You can order the PCBs directly at OSH Park, here is the link to the shared project:

https://www.oshpark.com/shared_projects/Tbhe3eJt

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(c) 04.2016 by Piotr Zapart www.hexeguitar.com

License: Creative Commons - Attribution - ShareAlike 3.0 http://creativecommons.org/licenses/by-sa/3.0/