MCP23S17 IO Port Expander Header File / Register

Summary
For a recent project the 16bit IO Expander, MCP23S17, from Microchip was enlisted for low voltage input scanning. 

Searching online, at the time of writing this blog, there were no projects using this part with sample code. 

Below is the header file that may be of use.

Microchip IO Expander QFN Package

Downloads

mcp23s17.h

Code

/******************************
* mcp23s17.h
******************************/

#ifndef mcp23s17_h
#define mcp23s17_h

typedef unsigned char   uint8;
    
#define MCP_READ   0x41     /* Read */
#define MCP_WRITE   0x40     /* Write */
#define Mode_8Bit     1         /* Addressing 8/16bit */
#define Mode_16bit    0

#ifdef Mode_16Bit
    /******************************
    * Control register for BANK=0
    ******************************/
    #define IODIRA        0x00      /* Data Direction Register for PORTA */
    #define IODIRB        0x01      /* Data Direction Register for PORTB */ 
    #define IPOLA         0x02      /* Input Polarity Register for PORTA */ 
    #define IPOLB         0x03      /* Input Polarity Register for PORTB */ 
    #define GPINTENA      0x04      /* Interrupt-on-change enable Register for PORTA */ 
    #define GPINTENB      0x05      /* Interrupt-on-change enable Register for PORTB */ 
    #define DEFVALA       0x06      /* Default Value Register for PORTA */    
    #define DEFVALB       0x07      /* Default Value Register for PORTB */      
    #define INTCONA       0x08      /* Interrupt-on-change control Register for PORTA */  
    #define INTCONB       0x09      /* Interrupt-on-change control Register for PORTB */      
    #define IOCON         0x0A      /* Configuration register for device */                      
    #define GPPUA         0x0C      /* 100kOhm pullup resistor register for PORTA (sets pin to input when set) */    
    #define GPPUB         0x0D      /* 100kOhm pullup resistor register for PORTB (sets pin to input when set) */      
    #define INTFA         0x0E      /* Interrupt flag Register for PORTA */        
    #define INTFB         0x0F      /* Interrupt flag Register for PORTB */    
    #define INTCAPA       0x10      /* Interrupt captured value Register for PORTA */  
    #define INTCAPB       0x11      /* Interrupt captured value Register for PORTB */    
    #define GPIOA         0x12      /* General purpose I/O Register for PORTA */  
    #define GPIOB         0x13      /* General purpose I/O Register for PORTB */ 
    #define OLATA         0x14      /* Output latch Register for PORTA */ 
    #define OLATB         0x15      /* Output latch Register for PORTB */
#endif

#ifdef Mode_8Bit
    /******************************
    * Control register for BANK=1
    ******************************/
    #define IODIRA        0x00      /* Data Direction Register for PORTA */
    #define IPOLA         0x01      /* Input Polarity Register for PORTA */  
    #define GPINTENA      0x02      /* Interrupt-on-change enable Register for PORTA */     
    #define DEFVALA       0x03      /* Default Value Register for PORTA */    
    #define INTCONA       0x04      /* Interrupt-on-change control Register for PORTA */     
    #define IOCONA        0x05      /* Configuration register for device */          
    #define GPPUA         0x06      /* 100kOhm pullup resistor register for PORTA (sets pin to input when set) */     
    #define INTFA         0x07      /* Interrupt flag Register for PORTA */
    #define INTCAPA       0x08      /* Interrupt captured value Register for PORTA */
    #define GPIOA         0x09      /* General purpose I/O Register for PORTA */  
    #define OLATA         0x0A      /* Output latch Register for PORTA */ 
    #define IODIRB        0x10      /* Data Direction Register for PORTB */ 
    #define IPOLB         0x11      /* Input Polarity Register for PORTB */ 
    #define GPINTENB      0x12      /* Interrupt-on-change enable Register for PORTB */
    #define DEFVALB       0x13      /* Default Value Register for PORTB */      
    #define INTCONB       0x14      /* Interrupt-on-change control Register for PORTB */
    #define IOCONB        0x15      /* Configuration register for device */  
    #define GPPUB         0x16      /* 100kOhm pullup resistor register for PORTB (sets pin to input when set) */        
    #define INTFB         0x17      /* Interrupt flag Register for PORTB */    
    #define INTCAPB       0x18      /* Interrupt captured value Register for PORTB */    
    #define GPIOB         0x19      /* General purpose I/O Register for PORTB */ 
    #define OLATB         0x1A      /* Output latch Register for PORTB */
#endif
    
/* Config bits - IOCON */
#define BANK  0x80
#define MIRROR  0x40
#define SEQOP  0x20
#define DISSLW  0x10
#define HAEN  0x08
#define ODR      0x04
#define INTPOL  0x02

/******************************
* Prototypes
******************************/
void MCP23S17_init();
void MCP23S17_write(uint8 address, uint8 value);
uint8 MCP23S17_read(uint8 address);
uint8 MCP23S17_verify(uint8 address, uint8 verify_data);
    
#endif
/* END */



Change Summary

Version 1.00 (10 February 2017)

• Created register mapping for MCP23S17, 8 and 16 bit modes