Port Expander Library

The mikroPascal 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 :
`var SPExpanderCS : sbit; bdata; sfr; external;`	Chip Select line.	`var SPExpanderCS : sbit at P1_1_bit;`
`var SPExpanderRST : sbit; bdata; sfr; external;`	Reset line.	`var SPExpanderRST : sbit at P1_0_bit;`

Expander_Init

Prototype	procedure Expander_Init(ModuleAddress : byte);
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 var SPExpanderCS : sbit at P1_1_bit; SPExpanderRST : sbit at P1_0_bit; ... SPI1_Init(); // initialize SPI module Expander_Init(0); // initialize port expander

Expander_Read_Byte

Prototype	function Expander_Read_Byte(ModuleAddress : byte; RegAddress : byte) : byte;
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 var read_data : byte; ... read_data := Expander_Read_Byte(0,1);

Expander_Write_Byte

Prototype	procedure Expander_Write_Byte(ModuleAddress: byte; RegAddress: byte; Data_: byte);
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	function Expander_Read_PortA(ModuleAddress: byte): byte;
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 var read_data : byte; ... Expander_Set_DirectionPortA(0,0xFF); // set expander's porta to be input ... read_data := Expander_Read_PortA(0);

Expander_Read_PortB

Prototype	function Expander_Read_PortB(ModuleAddress: byte): byte;
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 var read_data : byte; ... Expander_Set_DirectionPortB(0,0xFF); // set expander's portb to be input ... read_data := Expander_Read_PortB(0);

Expander_Read_PortAB

Prototype	function Expander_Read_PortAB(ModuleAddress: byte): word;
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 var read_data : word; ... Expander_Set_DirectionPortAB(0,0xFFFF); // set expander's porta and portb to be input ... read_data := Expander_Read_PortAB(0);

Expander_Write_PortA

Prototype	procedure Expander_Write_PortA(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Write_PortB(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Write_PortAB(ModuleAddress: byte; Data_: word);
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	procedure Expander_Set_DirectionPortA(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Set_DirectionPortB(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Set_DirectionPortAB(ModuleAddress: byte; Direction: word);
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	procedure Expander_Set_PullUpsPortA(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Set_PullUpsPortB(ModuleAddress: byte; Data_: byte);
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	procedure Expander_Set_PullUpsPortAB(ModuleAddress: byte; PullUps: word);
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.

program Soft_SPI;

var i, received_data : byte;

// Port Expander module connections
var SPExpanderRST : sbit at P0_6_bit;
var SPExpanderCS  : sbit at P0_7_bit;
// End Port Expander module connections

var SoftSpi_CLK : sbit at P0_2_bit;
var SoftSpi_SDI : sbit at P0_3_bit;
var SoftSpi_SDO : sbit at P0_4_bit;

begin
  i := 0;
  WDTCN   := 0xDE;                  // Sequence for
  WDTCN   := 0xAD;                  //   disabling the watchdog timer
  OSCICN  := 0x83;                  // Enable internal oscillator (24.5MHz divided by 1)
  P0MDOUT := P0MDOUT or %11010101;  // Configure P0.7(CS), P0.6(RST), P0.4(MOSI), P0.2(SCK)
                                    //   and P0.0(TX) pin as push-pull

  UART1_Init(4800);                 // Initialize UART module at 4800 bps
  Delay_ms(100);                    // Wait for UART module to stabilize
  UART1_Write_Text('Start');

  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 TRUE do                                 // Endless loop
    begin
      Expander_Write_PortA(0, i);               // Write i to expander's PORTA
      Inc(i);
      received_data := Expander_Read_PortB(0);  // Read expander's PORTB
      UART1_Write(received_data);               //   and send it to UART
      Delay_ms(100);
    end;
end.

HW Connection

Port Expander HW connection

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