Usar un 74HC165 con el MSP430 a través de USI

Conexión:

74HC165           MSP430
QH -------------> P1.7 (SDI)
CLK ------------> P1.5 (SCLK)
PL (o SH/LD) ---> P.1.2 (Cualquier pin vale).



InterruptVectors_init.c

/*
 *  ======== Timer0_A3 Interrupt Service Routine ======== 
 */
#pragma vector=TIMER0_A0_VECTOR
__interrupt void TIMER0_A0_ISR_HOOK(void)
{
    /* USER CODE START (section: TIMER0_A0_ISR_HOOK) */
    // Pedir al 74hc165 que lea las entradas
    P1OUT &= ~BIT2; // poner pin ld low
    P1OUT |= BIT2; // poner pin ld hight

    //Pedir al USI que lea 8 bits
    USICNT |= 8;

    /* USER CODE END (section: TIMER0_A0_ISR_HOOK) */
}


/*
 *  ======== USI Interrupt Service Routine ========
 */
#pragma vector=USI_VECTOR
__interrupt void USI_ISR_HOOK(void)
{
    /* USER CODE START (section: USI_ISR_HOOK) */
 USICTL1 &= ~USIIFG;
 clearDisplay();
 sendNumber(USISRL);
    /* USER CODE END (section: USI_ISR_HOOK) */
}

USI_init.c

/*
 *  This file is automatically generated and does not require a license
 */

#include <msp430.h>

/* USER CODE START (section: USI_init_c_prologue) */
/* User defined includes, defines, global variables and functions */
/* USER CODE END (section: USI_init_c_prologue) */

/*
 *  ======== USI_graceInit ========
 *  Initialize Universal Serial Interface
 */
void USI_graceInit(void)
{
    /* USER CODE START (section: USI_graceInit_prologue) */
    /* User initialization code */
    /* USER CODE END (section: USI_graceInit_prologue) */

    /* Disable USI */
    USICTL0 |= USISWRST;

    /* 
     * USI Control Register 0
     * 
     * USIPE7 -- USI function enabled
     * ~USIPE6 -- USI function disabled
     * USIPE5 -- USI function enabled
     * ~USILSB -- MSB first
     * USIMST -- Master mode
     * ~USIGE -- Output latch enable depends on shift clock
     * ~USIOE -- Output disabled
     * USISWRST -- USI logic held in reset state
     * 
     * Note: ~<BIT> indicates that <BIT> has value zero
     */
    USICTL0 = USIPE7 + USIPE5 + USIMST + USISWRST;

    /* 
     * USI Control Register 1
     * 
     * USICKPH -- Data is captured on the first SCLK edge and changed on the following edge
     * ~USII2C -- I2C mode disabled
     * ~USISTTIE -- Interrupt on START condition disabled
     * USIIE -- Interrupt enabled
     * ~USIAL -- No arbitration lost condition
     * ~USISTP -- No STOP condition received
     * ~USISTTIFG -- No START condition received. No interrupt pending
     * USIIFG -- Interrupt pending
     * 
     * Note: ~<BIT> indicates that <BIT> has value zero
     */
    USICTL1 = USICKPH + USIIE + USIIFG;

    /* 
     * USI Clock Control Register
     * 
     * USIDIV_0 -- Divide by 1
     * USISSEL_2 -- SMCLK
     * ~USICKPL -- Inactive state is low
     * ~USISWCLK -- Input clock is low
     * 
     * Note: ~<BIT> indicates that <BIT> has value zero
     */
    USICKCTL = USIDIV_0 + USISSEL_2;

    /* Enable USI */
    USICTL0 &= ~USISWRST;

    /* USER CODE START (section: USI_graceInit_epilogue) */
    /* User code */
    /* USER CODE END (section: USI_graceInit_epilogue) */
}

Usar un 74HC165 con el MSP430 y 8 interruptores

Nota:
LD --> PIN_PL
CLK--> PIN_CP
Q7 --> PIN_Q


74hc165.h

/*
 * 74hc165.h
 */

#ifndef FILE_74HC165_H_
#define FILE_74HC165_H_

#include "msp430.h"
#define PISO_IN_PORT P1IN
#define PISO_OUT_PORT P1OUT
#define PIN_PL BIT5
#define PIN_CP BIT4
#define PIN_Q BIT3

#define PIN_CP_HIGH PISO_OUT_PORT |= PIN_CP
#define PIN_CP_LOW PISO_OUT_PORT &= ~PIN_CP
#define PIN_PL_HIGH PISO_OUT_PORT |= PIN_PL
#define PIN_PL_LOW PISO_OUT_PORT &= ~PIN_PL

void init74hc165 (void);
unsigned char read74hc165(void);

#endif /* FILE_74HC165_H_ */

74hc165.c

/*
 * 74hc165.c
 */

#include "74hc165.h"

void pulseClock (void){
 PIN_CP_HIGH;
 PIN_CP_LOW;
}

void init74hc165 (void){
 PIN_PL_HIGH;
 PIN_CP_HIGH;
}

unsigned char read74hc165(void){

 unsigned char i;
 unsigned char ret = 0;
 volatile unsigned char readed;

 PIN_CP_HIGH;
 PIN_PL_LOW;
 PIN_CP_LOW;
 PIN_PL_HIGH;

 for (i=0; i < 8; i++){

  readed = PISO_IN_PORT;

  if ((readed & PIN_Q) == PIN_Q){
   ret = ret + (128 >> (i));
  }

  pulseClock();
 }

 return ret;
}