IOB-I2C-MCP23017

IOB I2C MCP23017 based IO Expander

The MCP23017 expander is an inexpensive and reliable device that supports up to 8x instances on a single I2C chain.

Specifications

Each board provides a latched set of 16x IO points, with each point being software selectable to be either an input or an output. The individual points are reasonably protected from the environment, and can source or sink 20 mA each (25mA absolute max).

Communication Protocol

```C++ enum MCP23017Registers { MCP23017_IODIRA = 0x00, MCP23017_IODIRB = 0x01, MCP23017_IPOLA = 0x02, MCP23017_IPOLB = 0x03, MCP23017_GPINTENA = 0x04, MCP23017_GPINTENB = 0x05, MCP23017_DEFVALA = 0x06, MCP23017_DEFVALB = 0x07, MCP23017_INTCONA = 0x08, MCP23017_INTCONB = 0x09, MCP23017_IOCONA = 0x0A, MCP23017_IOCONB = 0x0B, MCP23017_GPPUA = 0x0C, MCP23017_GPPUB = 0x0D, MCP23017_INTFA = 0x0E, MCP23017_INTFB = 0x0F, MCP23017_INTCAPA = 0x10, MCP23017_INTCAPB = 0x11, MCP23017_GPIOA = 0x12, MCP23017_GPIOB = 0x13, MCP23017_OLATA = 0x14, MCP23017_OLATB = 0x15, };

void I2Cexpander::init23017(uint8_t i2caddr, uint16_t dir) { if (i2caddr < base23017) { _i2c_address = base23017 + i2caddr; } else { _i2c_address = i2caddr; } Wire.beginTransmission(_i2c_address); Wire.write(MCP23017_IODIRA); Wire.write(0xff & dir); // Low byte Wire.endTransmission();

Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_IODIRB);
Wire.write(0xff & (dir >> 8));  // High byte
Wire.endTransmission();

// enable 100k pullups on all inputs...
Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPPUA);
Wire.write(0xff & dir);         // Low byte
Wire.endTransmission();

Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPPUB);
Wire.write(0xff & (dir >> 8));  // High byte
Wire.endTransmission(); }

uint32_t I2Cexpander::read23017() { uint32_t data = 0; Wire.beginTransmission(_i2c_address); Wire.write(MCP23017_GPIOA); Wire.endTransmission();

Wire.requestFrom(_i2c_address, (uint8_t)2, (uint8_t)1);
data = Wire.read();
data |= (Wire.read() << 8);
return data; } void I2Cexpander::write23017(uint32_t data) {
data = data | _config;
Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPIOA);
Wire.write(0xff & data);  //  low byte
Wire.write(data >> 8);    //  high byte
Wire.endTransmission(); } ``` See [I2Cexpander-lib](/pages/I2Cexpander "wikilink") for a more complete interface library.

Addressing The addres selection for the MCP23017 is simple - set the desired address (in binary) on the 3x address selection switches.

AD2|AD1|AD0|A6|A5|A4|A3|A2|A1|A0|ADDRESS (HEX) :—–:|:—–:|:—–:|:—–:|:—–:|:—–:|:—–:|:—–:|:—–:|:—–:|:—–: GND|GND|GND|0|1|0|0|0|0|0|0x20 GND|GND|V+|0|1|0|0|0|0|1|0x21 GND|V+|GND|0|1|0|0|0|1|0|0x22 GND|V+|V+|0|1|0|0|0|1|1|0x23 V+|GND|GND|0|1|0|0|1|0|0|0x24 V+|GND|V+|0|1|0|0|1|0|1|0x25 V+|V+|GND|0|1|0|0|1|1|0|0x26 V+|V+|V+|0|1|0|0|1|1|1|0x27

Download IOB-I2C-MCP23017 -
Download IOB-I2C-MCP23017_array.scr - Eagle SCRipt

IOB-I2C-MCP23017 Version 1.0

First built: 2020.09

The MCP23017 expander is an inexpensive and reliable device that supports up to 8x instances on a single I2C chain.

Specifications

Communication Protocol

Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_IODIRB);
Wire.write(0xff & (dir >> 8));  // High byte
Wire.endTransmission();

// enable 100k pullups on all inputs...
Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPPUA);
Wire.write(0xff & dir);         // Low byte
Wire.endTransmission();

Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPPUB);
Wire.write(0xff & (dir >> 8));  // High byte
Wire.endTransmission(); }

uint32_t I2Cexpander::read23017() { uint32_t data = 0; Wire.beginTransmission(_i2c_address); Wire.write(MCP23017_GPIOA); Wire.endTransmission();

Wire.requestFrom(_i2c_address, (uint8_t)2, (uint8_t)1);
data = Wire.read();
data |= (Wire.read() << 8);
return data; } void I2Cexpander::write23017(uint32_t data) {
data = data | _config;
Wire.beginTransmission(_i2c_address);
Wire.write(MCP23017_GPIOA);
Wire.write(0xff & data);  //  low byte
Wire.write(data >> 8);    //  high byte
Wire.endTransmission(); } ``` See [I2Cexpander-lib](/pages/I2Cexpander "wikilink") for a more complete interface library.