Port Expander Library

mikroPascal PRO for PIC32 provides a library for communication with the Microchip’s Port Expander MCP23S17 via SPI interface. Connections of the PIC32 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 :
`var SPExpanderRST : sbit; sfr; atomic; external;`	Reset line.	`var SPExpanderRST : sbit at LATF0_bit;`
`var SPExpanderCS : sbit; sfr; atomic; external;`	Chip Select line.	`var SPExpanderCS : sbit at LATF1_bit;`
`var SPExpanderRST_Direction : sbit; sfr; atomic; external;`	Direction of the Reset pin.	`var SPExpanderRST_Direction : sbit at TRISF0_bit;`
`var SPExpanderCS_Direction : sbit; sfr; atomic; external;`	Direction of the Chip Select pin.	`var SPExpanderCS_Direction : sbit at TRISF1_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_Set_DirectionPortA
Expander_Set_DirectionPortB
Expander_Set_DirectionPortAB
Expander_Set_PullUpsPortA
Expander_Set_PullUpsPortB
Expander_Set_PullUpsPortAB

Expander_Init

Prototype	procedure Expander_Init(ModuleAddress : byte);
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	Global variables : `SPExpanderCS`: Chip Select line `SPExpanderRST`: Reset line `SPExpanderCS_Direction`: Direction of the Chip Select pin `SPExpanderRST_Direction`: Direction of the Reset pin must be defined before using this function. SPI module needs to be initialized. See SPIx_Init and SPIx_Init_Advanced routines.
Example	// Port Expander module connections var SPExpanderRST : sbit at LATF0_bit; SPExpanderCS : sbit at LATF1_bit; SPExpanderRST_Direction : sbit at TRISF0_bit; SPExpanderCS_Direction : sbit at TRISF1_bit; // End of Port Expander module connections ... // If Port Expander Library uses SPI module SPI1_Init(); // Initialize SPI module used with PortExpander Expander_Init(0); // Initialize Port Expander
Notes	None.

Expander_Init_Advanced

Prototype	procedure Expander_Init_Advanced(var rstPort : dword; rstPin : byte; haen : byte);
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	`SPExpanderCS`: Chip Select line `SPExpanderRST`: Reset line `SPExpanderCS_Direction`: Direction of the Chip Select pin `SPExpanderRST_Direction`: Direction of the Reset pin must be defined before using this function. SPI module needs to be initialized. See SPIx_Init and SPIx_Init_Advanced routines.
Example	// Port Expander module connections sbit SPExpanderRST at LATF0_bit; sbit SPExpanderCS at LATF1_bit; sbit SPExpanderRST_Direction at TRISF0_bit; sbit SPExpanderCS_Direction at TRISF1_bit; // End Port Expander module connections ... // If Port Expander Library uses SPI1 module SPI1_Init(); // Initialize SPI1 module used with PortExpander Expander_Init_Advanced(PORTB, 0, 0); // Initialize Port Expander
Notes	None.

Expander_Read_Byte

Prototype	function Expander_Read_Byte(ModuleAddress, RegAddress : byte) : byte;
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 var read_data : byte; ... read_data := Expander_Read_Byte(0,1);
Notes	None.

Expander_Write_Byte

Prototype	procedure Expander_Write_Byte(ModuleAddress, RegAddress, Data : byte);
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,$FF);
Notes	None.

Expander_Read_PortA

Prototype	function Expander_Read_PortA(ModuleAddress : byte) : byte;
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 var read_data : byte; ... Expander_Set_DirectionPortA(0,$FF); // set expander's porta to be input ... read_data := Expander_Read_PortA(0);
Notes	None.

Expander_Read_PortB

Prototype	function Expander_Read_PortB(ModuleAddress : byte) : byte;
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 var read_data : byte; ... Expander_Set_DirectionPortB(0,$FF); // set expander's portb to be input ... read_data := Expander_Read_PortB(0);
Notes	None.

Expander_Read_PortAB

Prototype	function Expander_Read_PortAB(ModuleAddress : byte) : word;
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 var read_data : word; ... Expander_Set_DirectionPortAB(0,$FFFF); // set expander's porta and portb to be input ... read_data := Expander_Read_PortAB(0);
Notes	None.

Expander_Write_PortA

Prototype	procedure Expander_Write_PortA(ModuleAddress, Data : byte);
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,$00); // set expander's porta to be output ... Expander_Write_PortA(0, $AA);
Notes	None.

Expander_Write_PortB

Prototype	procedure Expander_Write_PortB(ModuleAddress, Data : byte);
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,$00); // set expander's portb to be output ... Expander_Write_PortB(0,$55);
Notes	None.

Expander_Write_PortAB

Prototype	procedure Expander_Write_PortAB(ModuleAddress : byte; Data : word);
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, $0000); // set expander's porta and portb to be output ... Expander_Write_PortAB(0, $AA55);
Notes	None.

Expander_Set_DirectionPortA

Prototype	procedure Expander_Set_DirectionPortA(ModuleAddress, Data : byte);
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,$00);
Notes	None.

Expander_Set_DirectionPortB

Prototype	procedure Expander_Set_DirectionPortB(ModuleAddress, Data : byte);
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,$FF);
Notes	None.

Expander_Set_DirectionPortAB

Prototype	procedure Expander_Set_DirectionPortAB(ModuleAddress, Direction : word);
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,$00FF);
Notes	None.

Expander_Set_PullUpsPortA

Prototype	procedure Expander_Set_PullUpsPortA(ModuleAddress, Data : byte);
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, $FF);
Notes	None.

Expander_Set_PullUpsPortB

Prototype	procedure Expander_Set_PullUpsPortB(ModuleAddress, Data : byte);
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	procedure Expander_Set_PullUpsPortAB(ModuleAddress : byte; PullUps : word);
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, $FFFF);
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

program PortExpander;

// Port Expander module connections
var SPExpanderRST : sbit at LATF0_bit;
    SPExpanderCS  : sbit at LATF1_bit;
    SPExpanderRST_Direction : sbit at TRISF0_bit;
    SPExpanderCS_Direction  : sbit at TRISF1_bit;
// End Port Expander module connections

var counter : word;

begin
  counter := 0;
  CHECON := 0x32;
  AD1PCFG := 0xFFFF;                      // Configure AN pins as digital

  TRISB  := 0x00;
  LATB   := 0xFF;

  // If Port Expander Library uses SPI1 module
  SPI2_Init_Advanced(_SPI_MASTER,_SPI_8_BIT, 4, _SPI_SS_DISABLE,_SPI_DATA_SAMPLE_MIDDLE,_SPI_CLK_IDLE_LOW,_SPI_ACTIVE_2_IDLE);

  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 ( TRUE ) do                       // Endless loop
    begin
      Expander_Write_PortA(0, counter);   // Write i to expander's PORTA
      Inc(counter);
      PORTB := Expander_Read_PortB(0);    // Read expander's PORTB and write it to LEDs
      Delay_ms(75);
    end;

end.

HW Connection

Port Expander HW connection

Want more examples and libraries?
Find them on