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Expand I/O Ports in ATmega16

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.
  • 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 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_Set_DirectionPortA
  • Expander_Set_DirectionPortB
  • Expander_Set_DirectionPortAB
  • Expander_Set_PullUpsPortA
  • Expander_Set_PullUpsPortB
  • Expander_Set_PullUpsPortAB

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 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. 
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

Expander_Init_Advanced

Prototype void Expander_Init_Advanced(char *rstPort, char rstPin, char haen);
Returns Nothing.
Description Initializes Port Expander using SPI communication.
Parameters :
  • rstPort: Port Expander's reset port
  • rstPin: Port Expander's reset pin
  • haen: Enable hardware addressing. Valid values :
    • 0 - hardware addressing disabled
    • 1 - hardware addressing enabled
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.
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

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.
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.
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.
Port Expander's PortA should be configured as input. 
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.
Port Expander's PortB should be configured as input. 
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.
Port Expander's PortA and PortB should be configured as inputs. 
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.
Port Expander's PortA should be configured as output. 
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.
Port Expander's PortB should be configured as output. 
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.
Port Expander's PortA and PortB should be configured as outputs. 
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. 
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. 
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. 
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. 
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.
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.
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 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


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