Port Expander Library

The mikroBasic PRO for PIC provides a library for communication with the Microchip’s Port Expander MCP23S17 via SPI interface. Connections of the PIC 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.

Library Dependency Tree

External dependencies of Port Expander Library

The following variables must be defined in all projects using Port Expander Library:	Description :	Example :
`dim SPExpanderRST as sbit sfr external`	Reset line.	`dim SPExpanderRST as sbit at RC0_bit`
`dim SPExpanderCS as sbit sfr external`	Chip Select line.	`dim SPExpanderCS as sbit at RC1_bit`
`dim SPExpanderRST_Direction as sbit sfr external`	Direction of the Reset pin.	`dim SPExpanderRST_Direction as sbit at TRISC0_bit`
`dim SPExpanderCS_Direction as sbit sfr external`	Direction of the Chip Select pin.	`dim SPExpanderCS_Direction as sbit at TRISC1_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	sub procedure Expander_Init(dim ModuleAddress as 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	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 SPI1_Init and SPI1_Init_Advanced routines.
Example	' Port Expander module connections dim SPExpanderCS as sbit at RC0_bit SPExpanderRST as sbit at RC1_bit SPExpanderCS_Direction as sbit at TRISC0_bit SPExpanderRST_Direction as sbit at TRISC1_bit ' End Port Expander module connections ... SPI1_Init() ' initialize SPI module Expander_Init(0) ' initialize Port Expander

Expander_Init_Advanced

Prototype	sub procedure Expander_Init_Advanced(dim byref rstPort as byte, dim rstPin, haen as byte)
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. See SPI1_Init and SPI1_Init_Advanced routines.
Example	' Port Expander module connections dim SPExpanderCS as sbit at RC0_bit SPExpanderRST as sbit at RC1_bit SPExpanderCS_Direction as sbit at TRISC0_bit SPExpanderRST_Direction as sbit at TRISC1_bit ' End Port Expander module connections ... SPI1_Init() ' initialize SPI module Expander_Init_Advanced(PORTC, 0, 0) ' initialize Port Expander

Expander_Read_Byte

Prototype	sub function Expander_Read_Byte(dim ModuleAddress as byte, dim RegAddress as byte) as 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 dim read_data as byte ... read_data = Expander_Read_Byte(0,1)

Expander_Write_Byte

Prototype	sub procedure Expander_Write_Byte(dim ModuleAddress as byte, dim RegAddress as byte, dim Data_ as 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	sub function Expander_Read_PortA(dim ModuleAddress as byte) as 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 dim read_data as byte ... Expander_Set_DirectionPortA(0,0xFF) ' set expander's porta to be input ... read_data = Expander_Read_PortA(0)

Expander_Read_PortB

Prototype	sub function Expander_Read_PortB(dim ModuleAddress as byte) as 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 dim read_data as byte ... Expander_Set_DirectionPortB(0,0xFF) ' set expander's portb to be input ... read_data = Expander_Read_PortB(0)

Expander_Read_PortAB

Prototype	sub function Expander_Read_PortAB(dim ModuleAddress as byte) as 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 dim read_data as 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	sub procedure Expander_Write_PortA(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Write_PortB(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Write_PortAB(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Set_DirectionPortA(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Set_DirectionPortB(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Set_DirectionPortAB(dim ModuleAddress as byte, dim Direction as 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	sub procedure Expander_Set_PullUpsPortA(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Set_PullUpsPortB(dim ModuleAddress as byte, dim Data_ as 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	sub procedure Expander_Set_PullUpsPortAB(dim ModuleAddress as byte, dim PullUps as 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.

Copy Code To Clipboard

program PortExpander

' Port Expander module connections
dim SPExpanderRST as sbit at RC0_bit
    SPExpanderCS  as sbit at RC1_bit
    SPExpanderRST_Direction as sbit at TRISC0_bit
    SPExpanderCS_Direction  as sbit at TRISC1_bit
' End Port Expander module connections

dim counter as byte' = 0

main:
  counter = 0
  ANSEL   = 0                          ' Configure AN pins as digital I/O
  ANSELH  = 0
  TRISB   = 0                          ' Set PORTB as output
  PORTB   = 0
  
  SPI1_init()
  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                           ' Endless loop
    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(100)
  wend
  
end.

HW Connection

Port Expander HW connection

Want more examples and libraries?
Find them on