Problema con la transmisión de datos de PIC18F45K20 (C18) a MCP23017

Actualmente estoy probando el expansor de E/S de 16 bits MCP23017 (dispositivo esclavo) usando un PIC18F45K20 con el compilador C18 para transmitir datos al MCP23017. Los pines de dirección (A0, A1 y A2) del MCP23017 están conectados a tierra. El reloj serie (SCL) funciona a 100 kHz.

Revisé el código de mi programa de pies a cabeza y no pude encontrar ningún problema en mi código a pesar de que se compiló sin errores.

Los problemas que enfrenté son:

• El MCP23017 no emite los datos transmitidos desde el PIC18F45K20 (el código de programa se muestra a continuación).

• La forma de onda SCL de PIC18F45K20 no es una onda cuadrada. Se midió con un osciloscopio.

  #include <stdio.h>
  #include <stdlib.h>
  #include <delays.h>
  #include <i2c.h>
  #include <p18f45k20.h>
  #include <sw_i2c.h>
  
  #define MCP_IODIR_A 0x00
  #define MCP_IPOL_A 0x02
  #define MCP_OLAT_A 0x14
  #define MCP_GPIO_A 0x12
  #define MCP_IOCON_A 0x0A
  #define MCP_GPINTEN_A 0x04
  
  /*
  * 
  */
  //----------------------------Global variable----------------------------
  
  
  // PIC18F45K20 Configuration Bit Settings
  
  // CONFIG1H
  #pragma config FOSC = INTIO67   // Oscillator Selection bits (Internal oscillator block, port function on RA6 and RA7)
  #pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor disabled)
  #pragma config IESO = OFF       // Internal/External Oscillator Switchover bit (Oscillator Switchover mode disabled)
  
  // CONFIG2L
  #pragma config PWRT = OFF       // Power-up Timer Enable bit (PWRT disabled)
  #pragma config BOREN = SBORDIS  // Brown-out Reset Enable bits (Brown-out Reset enabled in hardware only (SBOREN is disabled))
  #pragma config BORV = 30        // Brown Out Reset Voltage bits (VBOR set to 3.0 V nominal)
  
  // CONFIG2H
  #pragma config WDTEN = OFF      // Watchdog Timer Enable bit (WDT is controlled by SWDTEN bit of the WDTCON register)
  #pragma config WDTPS = 32768    // Watchdog Timer Postscale Select bits (1:32768)
  
  // CONFIG3H
  #pragma config CCP2MX = PORTC   // CCP2 MUX bit (CCP2 input/output is multiplexed with RC1)
  #pragma config PBADEN = ON      // PORTB A/D Enable bit (PORTB<4:0> pins are configured as analog input channels on Reset)
  #pragma config LPT1OSC = OFF    // Low-Power Timer1 Oscillator Enable bit  (Timer1 configured for higher power operation)
  #pragma config HFOFST = ON      // HFINTOSC Fast Start-up (HFINTOSC starts clocking the CPU without waiting for the oscillator to stablize.)
  #pragma config MCLRE = OFF      // MCLR Pin Enable bit (RE3 input pin enabled; MCLR disabled)
  
  // CONFIG4L
  #pragma config STVREN = ON      // Stack Full/Underflow Reset Enable bit (Stack full/underflow will cause Reset)
  #pragma config LVP = OFF        // Single-Supply ICSP Enable bit (Single-Supply ICSP disabled)
  #pragma config XINST = OFF      // Extended Instruction Set Enable bit (Instruction set extension and Indexed Addressing mode disabled (Legacy mode))
  
  // CONFIG5L
  #pragma config CP0 = OFF        // Code Protection Block 0 (Block 0 (000800-001FFFh) not code-protected)
  #pragma config CP1 = OFF        // Code Protection Block 1 (Block 1 (002000-003FFFh) not code-protected)
  #pragma config CP2 = OFF        // Code Protection Block 2 (Block 2 (004000-005FFFh) not code-protected)
  #pragma config CP3 = OFF        // Code Protection Block 3 (Block 3 (006000-007FFFh) not code-protected)
  
  // CONFIG5H
  #pragma config CPB = OFF        // Boot Block Code Protection bit (Boot block (000000-0007FFh) not code-protected)
  #pragma config CPD = OFF        // Data EEPROM Code Protection bit (Data EEPROM not code-protected)
  
  // CONFIG6L
  #pragma config WRT0 = OFF       // Write Protection Block 0 (Block 0 (000800-001FFFh) not write-protected)
  #pragma config WRT1 = OFF       // Write Protection Block 1 (Block 1 (002000-003FFFh) not write-protected)
  #pragma config WRT2 = OFF       // Write Protection Block 2 (Block 2 (004000-005FFFh) not write-protected)
  #pragma config WRT3 = OFF       // Write Protection Block 3 (Block 3 (006000-007FFFh) not write-protected)
  
  // CONFIG6H
  #pragma config WRTC = OFF       // Configuration Register Write Protection bit (Configuration registers (300000-3000FFh) not write-protected)
  #pragma config WRTB = OFF       // Boot Block Write Protection bit (Boot Block (000000-0007FFh) not write-protected)
  #pragma config WRTD = OFF       // Data EEPROM Write Protection bit (Data EEPROM not write-protected)
  
  // CONFIG7L
  #pragma config EBTR0 = OFF      // Table Read Protection Block 0 (Block 0(000800-001FFFh) not protected from table reads executed in other blocks)
  #pragma config EBTR1 = OFF      // Table Read Protection Block 1 (Block 1 (002000-003FFFh) not protected from table reads executed in other blocks)
  #pragma config EBTR2 = OFF      // Table Read Protection Block 2 (Block 2 (004000-005FFFh) not protected from table reads executed in other blocks)
  #pragma config EBTR3 = OFF      // Table Read Protection Block 3 (Block 3 (006000-007FFFh) not protected from table reads executed in other blocks)
  
  // CONFIG7H
  #pragma config EBTRB = OFF      // Boot Block Table Read Protection bit (Boot Block (000000-0007FFh) not protected from table reads executed in other blocks)
  
  void init_I2C()
  {
      DDRCbits.RC3 = 1; //Configure SCL as input
      DDRCbits.RC4 = 1; //Configure SDA as input
  
      // SSPSTAT Configuration (0x80)
      SSPSTATbits.SMP = 1;    //Slew rate control disabled
      SSPSTATbits.CKE = 0;    //SMBus disabled
      SSPSTATbits.D_A = 0;    //Reserved in master mode
      SSPSTATbits.P = 0;      //Stop bit was not detected last
      SSPSTATbits.S = 0;      //Start bit was not detected last
      SSPSTATbits.R_W = 0; 
      SSPSTATbits.UA = 0;     //Address doesnot need to be updated
      SSPSTATbits.BF = 0; 
  
      // SSPCON1 Configuration (0x28)
      SSPCON1bits.WCOL = 0;
      SSPCON1bits.SSPOV = 0;
      SSPCON1bits.SSPEN = 1;  //Serial port enabled
      SSPCON1bits.CKP = 0;    //Holds clock low
      SSPCON1bits.SSPM3 = 1;  //1000 = I2C Master mode
      SSPCON1bits.SSPM2 = 0;  //BitRate = FOSC/(4*(SPPADD+1))
      SSPCON1bits.SSPM1 = 0; 
      SSPCON1bits.SSPM0 = 0;                       
  
      // SSPADD Configuration
      SSPADD = 0x27;  //should be 0x27 for 100kHz
                      //SSPADD = [(FOSC/BitRate)/4]-1
  
      // SSPCON2 Configuration (0x00)
      SSPCON2bits.GCEN = 0;       //General call address disabled
      SSPCON2bits.ACKSTAT = 0;    //Acknowledge was received from slave
      SSPCON2bits.ACKDT = 0;      //Acknowledge
      SSPCON2bits.ACKEN = 0;      //Acknowledge sequence idle
      SSPCON2bits.RCEN = 0;       //Receive idle
      SSPCON2bits.PEN = 0;        //Stop condition idle
      SSPCON2bits.RSEN = 0;       //Repeated start condition idle
      SSPCON2bits.SEN = 0;
  }
  
  void MCP_write()
  {
       WriteI2C(0x40);
  }
  
  void MCP_read()
  {
       WriteI2C(0x41);
  }
  
  void MCP_addr()
  {
       StartI2C();
       MCP_write();
  }
  
  void init_MCP()
  {
       //IODIR A configuration
       MCP_addr();
       AckI2C();
       WriteI2C(MCP_IODIR_A);
       AckI2C();
       WriteI2C(0x00);
       StopI2C();
  
       //IPOL A configuration
       MCP_addr();
       AckI2C();
       WriteI2C(MCP_IPOL_A);
       AckI2C();
       WriteI2C(0x00);
       StopI2C();
  
       //OLAT A configuration
       MCP_addr();
       AckI2C();
       WriteI2C(MCP_OLAT_A);
       AckI2C();
       WriteI2C(0xFF);
       StopI2C();
  
       //IOCON A configuration
       MCP_addr();
       AckI2C();
       WriteI2C(MCP_IOCON_A);
       AckI2C();
       WriteI2C(0x00);
       StopI2C();
  
       //GPINTEN A configuration
       MCP_addr();
       AckI2C();
       WriteI2C(MCP_GPINTEN_A);
       AckI2C();
       WriteI2C(0x00);
       StopI2C();
  }
  
  
  //----------------------------Main program----------------------------
  void main(void)
  {
       OSCCON = 0x70;      //Set internal oscillation to 16 MHz
       TRISD=0;
       init_I2C();         //I2C initialization
       init_MCP();         //MCP23017 initialization
  
       while(1)
       {
           MCP_addr();
           AckI2C();
           WriteI2C(MCP_GPIO_A);
           AckI2C();
           WriteI2C(0x11);
           StopI2C();
        }
  }