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 /***************************************************************************
 * EM430F6137 Demo USCI_A0 SPI Interface to SCA3100 Accelerometer
 *
 * Uses TI EM430F6137 Development Tool
 *
 * Reads all 3 (x,y,z) axes
*/
#define XTAL 16000000L
#define TICKSPERMS (XTAL / 1000 / 5 - 1)
#define TICKSPERUS (TICKSPERMS / 1000)
#define SPICLOCK 500 // SPI clock = 500kHz
#define SPIFRAMEDELAY ((1000 / SPICLOCK) * 6) // SPI interframe delay [us] = 6 * Tsck
#define SPICSBDELAY ((1000 / SPICLOCK) / 2) // SCK -> CSB delay [us] = 0.5 * Tsck

// LIBRARIES
#include "cc430x613x.h"
#include "math.h"
// PORT DEFINITIONS
#define PORT_CSB_OUT P2OUT
#define PORT_CSB_DIR P2DIR

#define TX_BUFFER UCA0TXBUF
#define RX_BUFFER UCA0RXBUF

// PIN DEFINITIONS
#define PIN_CSB BIT7

//AXIS REG
#define X_LSB 0x04
#define X_MSB 0x05
#define Y_LSB 0x06
#define Y_MSB 0x07
#define Z_LSB 0x08
#define Z_MSB 0x09

// FUNCTION PROTOTYPES
unsigned char ReadRegister(unsigned char Address);
unsigned short realValues(unsigned short values);
void wait_ms(unsigned short ms);
void wait_us(unsigned short us);

unsigned short x_msb;
unsigned short x_lsb;
short x_value;
unsigned short y_msb;
unsigned short y_lsb;
short y_value;
unsigned short z_msb;
unsigned short z_lsb;
short z_value;
 
 void main(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop watchdog timer

  PMAPPWD = 0x02D52;                        // Get write-access to port mapping regs  
  P1MAP6 = PM_UCA0SIMO;                     // Map UCA0SIMO output to P1.6
  P1MAP5 = PM_UCA0SOMI;                     // Map UCA0SOMI output to P1.5
  P1MAP7 = PM_UCA0CLK;                      // Map UCA0CLK output to P1.7
  PMAPPWD = 0;                              // Lock port mapping registers  
                                            
  PORT_CSB_DIR |= PIN_CSB;
  PORT_CSB_OUT |= PIN_CSB;                     // Unselect gyro sensor
                                            
  P1DIR |= BIT5 + BIT6 + BIT7;              // ACLK, MCLK, SMCLK set out to pins
  P1SEL |= BIT5 + BIT6 + BIT7;              // P1.5,6,7 for debugging purposes.

  UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
  UCA0CTL0 |= UCMST+UCSYNC+UCCKPH+UCMSB;    // 3-pin, 8-bit SPI master
                                            // Clock polarity high, MSB
  UCA0CTL1 |= UCSSEL0;                      // SMCLK
  UCA0BR0 = 0x02;                           // /2
  UCA0BR1 = 0;                              //
  UCA0MCTL = 0;                             // No modulation
  UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
  UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX interrupt

while(1)
 {
 x_lsb = ReadRegister(X_LSB);
 x_msb = ReadRegister(X_MSB);
 x_value = (x_msb<<8) | x_lsb;
 x_value = realValues(x_value);
 
 y_lsb = ReadRegister(Y_LSB);
 y_msb = ReadRegister(Y_MSB);
 y_value = (y_msb<<8) | y_lsb;
 y_value=realValues(y_value);
 
 z_lsb = ReadRegister(Z_LSB);
 z_msb = ReadRegister(Z_MSB);
 z_value = (z_msb<<8) | z_lsb;
 z_value=realValues(z_value);
 
 wait_ms(10);
}
}
// Read a byte from the gyro sensor
unsigned char ReadRegister(unsigned char Address)
{
unsigned char Result;
Address <<= 2;                     // Address to be shifted left by 2 and RW bit to be reset
PORT_CSB_OUT &= ~PIN_CSB;         // Select gyro sensor
Result = RX_BUFFER;             // Read RX buffer just to clear interrupt flag
TX_BUFFER = Address;             // Write address to TX buffer
while (!(UCA0IFG&UCRXIFG));     // Wait until new data was written into RX buffer
Result = RX_BUFFER;             // Read RX buffer just to clear interrupt flag
TX_BUFFER = 0;                     // Write dummy data to TX buffer
while (!(UCA0IFG&UCRXIFG));     // Wait until new data was written into RX buffer
Result = RX_BUFFER;                 // Read RX buffer
wait_us(SPICSBDELAY);             // Delay to satisfy 1/2 clk period delay from
                                // falling edge of clk to CSB
PORT_CSB_OUT |= PIN_CSB;         // Deselect gyro sensor
wait_us(SPIFRAMEDELAY);         // Delay to satisfy 6x clk period for CS high state
return Result;                     // Return new data from RX buffer
}

void wait_ms(unsigned short ms)
{
 unsigned short a, b;
 for (a = ms; a > 0; a--) // outer loop takes 5 ck per round
 for (b = TICKSPERMS; b > 0; b--) // inner loop takes 5 ck per round
 asm(" nop");
}
// wait us
void wait_us(unsigned short us)
{
 unsigned short a;
 us *= TICKSPERUS;
 for (a = us; a > 0; a--) // loop takes 5 ck per round
 asm(" nop");
}

unsigned int shift(unsigned short thisData, int thisBit)
{
unsigned short data;
data=thisData>>(thisBit-1);
data=data&0x01;
return data;
}
unsigned short realValues(unsigned short values)
{
  short table[14];
  int i;
  int bitti=3;
  unsigned short rdy;
  for(i=0;i<14;i++)
  {
    
    table[i]= shift(values,bitti);
    bitti++;
  }
rdy=(10/9)*(-table[13]*pow(2,13)+table[12]*pow(2,12)+table[11]*pow(2,11)+table[10]*pow(2,10)+table[9]*pow(2,9)+table[8]*pow(2,8)+table[7]*pow(2,7)+table[6]*pow(2,6)+table[5]*pow(2,5)+table[4]*pow(2,4)+table[3]*pow(2,3)+table[2]*pow(2,2)+table[1]*2+table[0]);

return rdy;
}