Port Expander Library

The mikroC PRO for 8051 provides a library for communication with the Microchip’s Port Expander MCP23S17 via SPI interface. Connections of the 8051 compliant MCU and MCP23S17 is given on the schematic at the bottom of this page.

Notes:

Library uses the SPI module for communication. The user must initialize SPI module before using the Port Expander Library.
Library does not use Port Expander interrupts.

External dependencies of Port Expander Library

The following variables must be defined in all projects using Port Expander Library:	Description :	Example :
`extern sfr sbit bdata SPExpanderCS;`	Chip Select line.	`sbit SPExpanderCS at P1_1_bit;`
`extern sfr sbit bdata SPExpanderRST;`	Reset line.	`sbit SPExpanderRST at P1_0_bit;`

Expander_Init

Prototype	void Expander_Init(char ModuleAddress);
Returns	Nothing.
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
Requires	`SPExpanderCS` and `SPExpanderRST` variables must be defined before using this function. SPI module needs to be initialized. See SPIx_Init and SPIx_Init_Advanced routines.
Example	// port expander pinout definition sbit SPExpanderRST at P1_0_bit; sbit SPExpanderCS at P1_1_bit; ... SPI1_Init(); // initialize SPI module Expander_Init(0); // initialize port expander

Expander_Read_Byte

Prototype	char Expander_Read_Byte(char ModuleAddress, char RegAddress);
Returns	Byte read.
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
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);

Expander_Write_Byte

Prototype	void Expander_Write_Byte(char ModuleAddress, char RegAddress, char Data);
Returns	Nothing.
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
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);

Expander_Read_PortA

Prototype	char Expander_Read_PortA(char ModuleAddress);
Returns	Byte read.
Description	The function reads byte from Port Expander's PortA. Parameters : `ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
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);

Expander_Read_PortB

Prototype	char Expander_Read_PortB(char ModuleAddress);
Returns	Byte read.
Description	The function reads byte from Port Expander's PortB. Parameters : `ModuleAddress:` Port Expander hardware address, see schematic at the bottom of this page
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);

Expander_Read_PortAB

Prototype	unsigned int Expander_Read_PortAB(char ModuleAddress);
Returns	Word read.
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
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);

Expander_Write_PortA

Prototype	void Expander_Write_PortA(char ModuleAddress, char Data_);
Returns	Nothing.
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
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);

Expander_Write_PortB

Prototype	void Expander_Write_PortB(char ModuleAddress, char Data_);
Returns	Nothing.
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
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);

Expander_Write_PortAB

Prototype	void Expander_Write_PortAB(char ModuleAddress, unsigned int Data_);
Returns	Nothing.
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
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);

Expander_Set_DirectionPortA

Prototype	void Expander_Set_DirectionPortA(char ModuleAddress, char Data_);
Returns	Nothing.
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.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA to be output Expander_Set_DirectionPortA(0,0x00);

Expander_Set_DirectionPortB

Prototype	void Expander_Set_DirectionPortB(char ModuleAddress, char Data_);
Returns	Nothing.
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.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB to be input Expander_Set_DirectionPortB(0,0xFF);

Expander_Set_DirectionPortAB

Prototype	void Expander_Set_DirectionPortAB(char ModuleAddress, unsigned int Direction);
Returns	Nothing.
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.
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);

Expander_Set_PullUpsPortA

Prototype	void Expander_Set_PullUpsPortA(char ModuleAddress, char Data_);
Returns	Nothing.
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.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTA pull-up resistors Expander_Set_PullUpsPortA(0, 0xFF);

Expander_Set_PullUpsPortB

Prototype	void Expander_Set_PullUpsPortB(char ModuleAddress, char Data_);
Returns	Nothing.
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.
Requires	Port Expander must be initialized. See Expander_Init.
Example	// Set Port Expander's PORTB pull-up resistors Expander_Set_PullUpsPortB(0, 0xFF);

Expander_Set_PullUpsPortAB

Prototype	void Expander_Set_PullUpsPortAB(char ModuleAddress, unsigned int PullUps);
Returns	Nothing.
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.
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);

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.

// Port Expander module connections
sbit  SPExpanderRST at P1_0_bit;
sbit  SPExpanderCS  at P1_1_bit;
// End Port Expander module connections

// Software SPI connections
sbit SoftSpi_CLK at P1_7_bit;
sbit SoftSpi_SDI at P1_6_bit;
sbit SoftSpi_SDO at P1_5_bit;
// End Software SPI connections

char (*SPI_Rd_Ptr)(char);                // Pointer to SPI_Read function
                                         //   used by Port Expander Library
unsigned char i = 0;

void main() {

  SPI_Rd_Ptr = Soft_SPI_Read;            // Link Port Expander Library to Software SPI library

  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
    P2 = Expander_Read_PortB(0);         // Read expander's PORTB and write it to PORT2 LEDs
    Delay_ms(100);
  }
  
}

HW Connection

Port Expander HW connection

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