Port Expander Library

The mikroC PRO for AVR provides a library for communication with the Microchip’s Port Expander MCP23S17 via SPI interface. Connections of the AVR compliant MCU and MCP23S17 is given on the schematic at the bottom of this page.

Important :

The library uses the SPI module for communication. User must initialize the appropriate SPI module before using the Port Expander Library.
For MCUs with multiple SPI modules it is possible to initialize all of them and then switch by using the SPI_Set_Active() function. See the SPI Library functions.
Library does not use Port Expander interrupts.

Library Dependency Tree

External dependencies of Port Expander Library

The following variables must be defined in all projects using Port Expander Library:	Description :	Example :
`extern sfr sbit SPExpanderRST;`	Reset line.	`sbit SPExpanderRST at PORTB0_bit;`
`extern sfr sbit SPExpanderCS;`	Chip Select line.	`sbit SPExpanderCS at PORTB1_bit;`
`extern sfr sbit SPExpanderRST_Direction;`	Direction of the Reset pin.	`sbit SPExpanderRST_Direction at DDB0_bit;`
`extern sfr sbit SPExpanderCS_Direction;`	Direction of the Chip Select pin.	`sbit SPExpanderCS_Direction at DDB1_bit;`

Library Routines

Expander_Init
Expander_Init_Advanced
Expander_Read_Byte
Expander_Write_Byte
Expander_Read_PortA
Expander_Read_PortB
Expander_Read_PortAB
Expander_Write_PortA
Expander_Write_PortB
Expander_Write_PortAB
Expander_SetBit_PortA
Expander_ClrBit_PortA
Expander_ToggleBit_PortA
Expander_SetBit_PortB
Expander_ClrBit_PortB
Expander_ToggleBit_PortB
Expander_Set_DirectionPortA
Expander_Set_DirectionPortB
Expander_Set_DirectionPortAB
Expander_Set_InputDirPortA
Expander_Set_OutputDirPortA
Expander_Set_InputDirPortB
Expander_Set_OutputDirPortB
Expander_Set_PullUpsPortA
Expander_Set_PullUpsPortB
Expander_Set_PullUpsPortAB
Expander_SetBits
Expander_ClrBits
Expander_ToggleBits

Expander_Init

Prototype	void Expander_Init(char ModuleAddress);
Description	Initializes Port Expander using SPI communication. Port Expander module settings : hardware addressing enabled automatic address pointer incrementing disabled (byte mode) BANK_0 register adressing slew rate enabled
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
Returns	Nothing.
Requires	External dependencies of the library from the top of the page must be defined before using this function. SPI module needs to be initialized. See SPI1_Init and SPI1_Init_Advanced routines.
Example	// Port Expander module connections sbit SPExpanderRST at PORTB0_bit; sbit SPExpanderCS at PORTB1_bit; sbit SPExpanderRST_Direction at DDB0_bit; sbit SPExpanderCS_Direction at DDB1_bit; // End Port Expander module connections ... // If Port Expander Library uses SPI1 module SPI1_Init(); // Initialize SPI module used with PortExpander Expander_Init(0); // Initialize Port Expander
Notes	None.

Expander_Init_Advanced

Prototype	void Expander_Init_Advanced(char rstPort, char* rstPin, char haen);
Description	Initializes Port Expander using SPI communication.
Parameters	`rstPort:` Port Expander's reset port `rstPin:` Port Expander's reset pin `haen:` Port Expander's hardware address
Returns	Nothing.
Requires	External dependencies of the library from the top of the page must be defined before using this function. SPI module needs to be initialized. See SPI1_Init and SPI1_Init_Advanced routines.
Example	// Port Expander module connections sbit SPExpanderRST at RC0_bit; sbit SPExpanderCS at RC1_bit; sbit SPExpanderRST_Direction at TRISC0_bit; sbit SPExpanderCS_Direction at TRISC1_bit; // End Port Expander module connections ... ANSEL = 0; // Configure AN pins as digital I/O ANSELH = 0; // If Port Expander Library uses SPI module SPI1_Init(); // Initialize SPI module used with PortExpander Expander_Init_Advanced(&PORTB, 0, 0); // Initialize Port Expander
Notes	None.

Expander_Read_Byte

Prototype	char Expander_Read_Byte(char ModuleAddress, char RegAddress);
Description	The function reads byte from Port Expander.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `RegAddress:` Port Expander's internal register address
Returns	Byte read.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Read a byte from Port Expander's register char read_data; ... read_data = Expander_Read_Byte(0,1);
Notes	None.

Expander_Write_Byte

Prototype	void Expander_Write_Byte(char ModuleAddress, char RegAddress, char data_);
Description	Routine writes a byte to Port Expander.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `RegAddress:` Port Expander's internal register address `Data:` data to be written
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Write a byte to the Port Expander's register Expander_Write_Byte(0,1,0xFF);
Notes	None.

Expander_Read_PortA

Prototype	char Expander_Read_PortA(char ModuleAddress);
Description	The function reads byte from Port Expander's PortA.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
Returns	Byte read.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA should be configured as input. See Expander_Set_DirectionPortA and Expander_Set_DirectionPortAB routines.
Example	// Read a byte from Port Expander's PORTA char read_data; ... Expander_Set_DirectionPortA(0,0xFF); // set expander's porta to be input ... read_data = Expander_Read_PortA(0);
Notes	None.

Expander_Read_PortB

Prototype	char Expander_Read_PortB(char ModuleAddress);
Description	The function reads byte from Port Expander's PortB.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
Returns	Byte read.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortB should be configured as input. See Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Read a byte from Port Expander's PORTB char read_data; ... Expander_Set_DirectionPortB(0,0xFF); // set expander's portb to be input ... read_data = Expander_Read_PortB(0);
Notes	None.

Expander_Read_PortAB

Prototype	unsigned int Expander_Read_PortAB(char ModuleAddress);
Description	The function reads word from Port Expander's ports. PortA readings are in the higher byte of the result. PortB readings are in the lower byte of the result.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
Returns	Word read.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA and PortB should be configured as inputs. See Expander_Set_DirectionPortA, Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Read a byte from Port Expander's PORTA and PORTB unsigned int read_data; ... Expander_Set_DirectionPortAB(0,0xFFFF); // set expander's porta and portb to be input ... read_data = Expander_Read_PortAB(0);
Notes	None.

Expander_Write_PortA

Prototype	void Expander_Write_PortA(char ModuleAddress, char Data_);
Description	The function writes byte to Port Expander's PortA.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data to be written
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA should be configured as output. See Expander_Set_DirectionPortA and Expander_Set_DirectionPortAB routines.
Example	// Write a byte to Port Expander's PORTA ... Expander_Set_DirectionPortA(0,0x00); // set expander's porta to be output ... Expander_Write_PortA(0, 0xAA);
Notes	None.

Expander_Write_PortB

Prototype	void Expander_Write_PortB(char ModuleAddress, char Data_);
Description	The function writes byte to Port Expander's PortB.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data to be written
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortB should be configured as output. See Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Write a byte to Port Expander's PORTB ... Expander_Set_DirectionPortB(0,0x00); // set expander's portb to be output ... Expander_Write_PortB(0, 0x55);
Notes	None.

Expander_Write_PortAB

Prototype	void Expander_Write_PortAB(char ModuleAddress, unsigned int Data_);
Description	The function writes word to Port Expander's ports.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data to be written. Data to be written to PortA are passed in `Data`'s higher byte. Data to be written to PortB are passed in `Data`'s lower byte
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA and PortB should be configured as outputs. See Expander_Set_DirectionPortA, Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Write a byte to Port Expander's PORTA and PORTB ... Expander_Set_DirectionPortAB(0,0x0000); // set expander's porta and portb to be output ... Expander_Write_PortAB(0, 0xAA55);
Notes	None.

Expander_SetBit_PortA

Prototype	void Expander_SetBit_PortA(char ModuleAddress, BitMask : word);
Description	The function sets bits designated by the `BitMask` parameter to Port Expander's PortA.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA should be configured as output. See Expander_Set_DirectionPortA and Expander_Set_DirectionPortAB routines.
Example	// Sets lower nibble of the PortA ... Expander_Set_DirectionPortA(0, $0000); // set expander's PortA to be output ... Expander_SetBit_PortA(0, 0x0F);
Notes	None.

Expander_ClrBit_PortA

Prototype	void Expander_ClrBit_PortA(char ModuleAddress, BitMask : word);
Description	The function clears bits designated by the `BitMask` parameter in Port Expander's PortA.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA should be configured as output. See Expander_Set_DirectionPortA and Expander_Set_DirectionPortAB routines.
Example	// Clears lower nibble of the PortA ... Expander_Set_DirectionPortA(0, $0000); // set expander's PortA to be output ... Expander_ClrBit_PortA(0, 0x0F);
Notes	None.

Expander_ToggleBit_PortA

Prototype	void Expander_ToggleBit_PortA(char ModuleAddress, BitMask : word);
Description	The function toggles bits designated by the `BitMask` parameter in Port Expander's PortA.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortA should be configured as output. See Expander_Set_DirectionPortA and Expander_Set_DirectionPortAB routines.
Example	// Toggles lower nibble of the PortA ... Expander_Set_DirectionPortA(0, $0000); // set expander's PortA to be output ... Expander_ToggleBit_PortA(0, 0x0F);
Notes	None.

Expander_SetBit_Portb

Prototype	void Expander_SetBit_PortB(char ModuleAddress, BitMask : word);
Description	The function sets bits designated by the `BitMask` parameter to Port Expander's PortB.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortB should be configured as output. See Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Sets lower nibble of the PortB ... Expander_Set_DirectionPortB(0, $0000); // set expander's PortB to be output ... Expander_SetBit_PortB(0, 0x0F);
Notes	None.

Expander_ClrBit_PortB

Prototype	void Expander_ClrBit_PortB(char ModuleAddress, BitMask : word);
Description	The function clears bits designated by the `BitMask` parameter in Port Expander's PortB.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortB should be configured as output. See Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Clears lower nibble of the PortB ... Expander_Set_DirectionPortB(0, $0000); // set expander's PortB to be output ... Expander_ClrBit_PortB(0, 0x0F);
Notes	None.

Expander_ToggleBit_PortB

Prototype	void Expander_ToggleBit_PortB(char ModuleAddress, BitMask : word);
Description	The function toggles bits designated by the `BitMask` parameter in Port Expander's PortB.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init. Port Expander's PortB should be configured as output. See Expander_Set_DirectionPortB and Expander_Set_DirectionPortAB routines.
Example	// Toggles lower nibble of the PortB ... Expander_Set_DirectionPortB(0, $0000); // set expander's PortB to be output ... Expander_ToggleBit_PortB(0, 0x0F);
Notes	None.

Expander_Set_DirectionPortA

Prototype	void Expander_Set_DirectionPortA(char ModuleAddress, char Data_);
Description	The function sets Port Expander's PortA direction.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data to be written to the PortA direction register. Each bit corresponds to the appropriate pin of the PortA register. Set bit designates corresponding pin as input. Cleared bit designates corresponding pin as output.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA to be output Expander_Set_DirectionPortA(0,0x00);
Notes	None.

Expander_Set_DirectionPortB

Prototype	void Expander_Set_DirectionPortB(char ModuleAddress, char Data_);
Description	The function sets Port Expander's PortB direction.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data to be written to the PortB direction register. Each bit corresponds to the appropriate pin of the PortB register. Set bit designates corresponding pin as input. Cleared bit designates corresponding pin as output.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB to be input Expander_Set_DirectionPortB(0,0xFF);
Notes	None.

Expander_Set_DirectionPortAB

Prototype	void Expander_Set_DirectionPortAB(char ModuleAddress, unsigned int Direction);
Description	The function sets Port Expander's PortA and PortB direction.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Direction:` data to be written to direction registers. Data to be written to the PortA direction register are passed in `Direction`'s higher byte. Data to be written to the PortB direction register are passed in `Direction`'s lower byte. Each bit corresponds to the appropriate pin of the PortA/PortB register. Set bit designates corresponding pin as input. Cleared bit designates corresponding pin as output.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA to be output and PORTB to be input Expander_Set_DirectionPortAB(0,0x00FF);
Notes	None.

Expander_Set_InputDirPortA

Prototype	void Expander_Set_InputDirPortA(ModuleAddress, char BitMask);
Description	The function sets the desired Port Expander's PortA pins as input according to the `BitMask` parameter.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA lower four pins as input : Expander_Set_InputDirPortA(0, 0x0F);
Notes	None.

Expander_Set_OutputDirPortA

Prototype	void Expander_Set_OutputDirPortA(ModuleAddress, char BitMask);
Description	The function sets the desired Port Expander's PortB pins as input according to the `BitMask` parameter.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA lower four pins as output : Expander_Set_OutputDirPortA(0, 0x0F);
Notes	None.

Expander_Set_InputDirPortB

Prototype	void Expander_Set_InputDirPortB(ModuleAddress, char BitMask);
Description	The function sets the desired Port Expander's PortB pins as input according to the `BitMask` parameter.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB lower four pins as input : Expander_Set_InputDirPortB(0, 0x0F);
Notes	None.

Expander_Set_OutputDirPortB

Prototype	void Expander_Set_OutputDirPortB(ModuleAddress, char BitMask);
Description	The function sets the desired Port Expander's PortB pins as input according to the `BitMask` parameter.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB lower four pins as output : Expander_Set_OutputDirPortB(0, 0x0F);
Notes	None.

Expander_Set_PullUpsPortA

Prototype	void Expander_Set_PullUpsPortA(char ModuleAddress, char Data_);
Description	The function sets Port Expander's PortA pull up/down resistors.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data for choosing pull up/down resistors configuration. Each bit corresponds to the appropriate pin of the PortA register. Set bit enables pull-up for corresponding pin.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA pull-up resistors Expander_Set_PullUpsPortA(0, 0xFF);
Notes	None.

Expander_Set_PullUpsPortB

Prototype	void Expander_Set_PullUpsPortB(char ModuleAddress, char Data_);
Description	The function sets Port Expander's PortB pull up/down resistors.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `Data:` data for choosing pull up/down resistors configuration. Each bit corresponds to the appropriate pin of the PortB register. Set bit enables pull-up for corresponding pin.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB pull-up resistors Expander_Set_PullUpsPortB(0, 0xFF);
Notes	None.

Expander_Set_PullUpsPortAB

Prototype	void Expander_Set_PullUpsPortAB(char ModuleAddress, unsigned int PullUps);
Description	The function sets Port Expander's PortA and PortB pull up/down resistors.
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `PullUps:` data for choosing pull up/down resistors configuration. PortA pull up/down resistors configuration is passed in `PullUps`'s higher byte. PortB pull up/down resistors configuration is passed in `PullUps`'s lower byte. Each bit corresponds to the appropriate pin of the PortA/PortB register. Set bit enables pull-up for corresponding pin.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA and PORTB pull-up resistors Expander_Set_PullUpsPortAB(0, 0xFFFF);
Notes	None.

Expander_SetBits

Prototype	void Expander_SetBits(char ModuleAddress, char RegAddress, char BitMask);
Description	The function sets bits designated by the `BitMask` parameter to Port Expander's internal register (`RegAddress` parameter).
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `RegAddress:` Port Expander's internal register address `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Sets lower nibble at the register located on the address 1 of the Port Expander Expander_SetBits(0, 1, 0x0F);
Notes	None.

Expander_ClrBits

Prototype	void Expander_ClrBits(char ModuleAddress, char RegAddress, char BitMask);
Description	The function clears bits designated by the `BitMask` parameter in the Port Expander's internal register (`RegAddress` parameter).
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `RegAddress:` Port Expander's internal register address `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Clears lower nibble in the register located on the address 1 of the Port Expander Expander_ClrBits(0, 1, 0x0F);
Notes	None.

Expander_ToggleBits

Prototype	void Expander_ToggleBits(char ModuleAddress, char RegAddress, char BitMask);
Description	The function toggles bits designated by the `BitMask` parameter in the Port Expander's internal register (`RegAddress` parameter).
Parameters	`ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page `RegAddress:` Port Expander's internal register address `BitMask:` appropriate bitmask.
Returns	Nothing.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Toggles lower nibble in the register located on the address 1 of the Port Expander Expander_ToggleBits(0, 1, 0x0F);
Notes	None.

Library Example

The example demonstrates how to communicate with Port Expander MCP23S17.

Note that Port Expander pins A2 A1 A0 are connected to GND so Port Expander Hardware Address is 0.

Copy Code To Clipboard

// Port Expander module connections
sbit  SPExpanderRST at PORTB0_bit;
sbit  SPExpanderCS  at PORTB1_bit;
sbit  SPExpanderRST_Direction at DDB0_bit;
sbit  SPExpanderCS_Direction  at DDB1_bit;
// End Port Expander module connections

unsigned char i = 0;

void main() {

  DDRC = 0xFF;                           // Set PORTC as output

  // If Port Expander Library uses SPI1 module
  SPI1_Init();                           // Initialize SPI module used with PortExpander

//  // If Port Expander Library uses SPI2 module
//  SPI2_Init();                           // Initialize SPI module used with PortExpander

  Expander_Init(0);                      // Initialize Port Expander

  Expander_Set_DirectionPortA(0, 0x00);  // Set Expander's PORTA to be output

  Expander_Set_DirectionPortB(0,0xFF);   // Set Expander's PORTB to be input
  Expander_Set_PullUpsPortB(0,0xFF);     // Set pull-ups to all of the Expander's PORTB pins

  while(1) {                             // Endless loop
    Expander_Write_PortA(0, i++);        // Write i to expander's PORTA
    PORTC = Expander_Read_PortB(0);      // Read expander's PORTB and write it to LEDs
    Delay_ms(50);
  }
  
}

HW Connection

Port Expander HW connection

Want more examples and libraries?
Find them on