SPI Question

Alex,

This is my very basic code, without using any TX or RX interrupts. 

I used BIT1 of Port 4 for Chip select and BIT2 as power for the ADXL345. The MCLK was running at 8 MHz and the SMCLK at 4 MHz. I had some problems with the ADXL345 ground. 

I know it may sound stupid, but try disconnecting the ground from the ADXL345 and read again. This happened to me, the ADXL345 was not working correctly whenever I had ground connected to the MSP430 GND(Might have been an issue with my wiring).

Make adjustments for your chip as this code was written for MSP430F2274.

//******************************************************************************
// ADXL345 -SPI- MSP430F2274//
// 8 bit- resolution //
// Left Justified //
//******************************************************************************
#include "msp430f2274.h"

#define spi_on P4OUT &= ~0x2; // Select the slave device
#define spi_off P4OUT |= 0x2; // Release the slave device
#define wait_tm while ((UCB0STAT & UCBUSY)); // Transmission Done?

#define led_delay __delay_cycles(400000);

#define delay_2 __delay_cycles(10);
#define delay_4 __delay_cycles(200000);

unsigned int i,k,l=0;
char x1,x0,y1,y0,z1,z0;

char tick,ints,devid,dataform,power,fifo,datax,datay,dataz,bufx[60],bufy[60],bufz[60];

void main(void)
{

char read_byte(char byte);
void get_allaxis(char mbyte);
void write_byte(char addr,char data);

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

BCSCTL1 = CALBC1_8MHZ; // Set DCO to 8MHz
DCOCTL = CALDCO_8MHZ;
BCSCTL2 |=0x42; // Set MCLK to 8 MHz and SMCLK to 4Mhz

__bis_SR_register(OSCOFF); // Turn oscilater off
P3SEL |= 0xe; // P3.1,P3.2,P3.3 USCI_B0 option select

P4DIR |= 0x6; // CS P4.1,Power P4.2 to be output
P4OUT &= ~0x6;

// SPI Definations
UCB0CTL1 = UCSWRST; // **Put state machine in reset**
UCB0CTL0 |= UCCKPL + UCMSB + UCMST + UCSYNC; // 3-pin, 8-bit SPI master
UCB0CTL0 &= ~UC7BIT;
UCB0CTL1 |= UCSSEL_2; // Select SMCLK as CLK
UCB0BR0 |= 0x02;
UCB0BR1 = 0;
UCB0CTL1 &= ~UCSWRST; // **Initialize USCI state machine**

P4OUT |= BIT2;
led_delay;
P4OUT &= ~BIT2;
led_delay;
P4OUT |= BIT2;

delay_3;
// Read the ID//
spi_on;
devid = read_byte(0x80);
spi_off;
delay_2;

// write to the data format//
spi_on;
write_byte(0x31,0x07);
spi_off;
delay_2;

// make sure write worked//
spi_on;
dataform = read_byte(0xb1);
spi_off;
delay_2;

// write to the power ctl//
spi_on;
write_byte(0x2d,0x08);
spi_off;
delay_2;

//read the power ctl//
spi_on;
power = read_byte(0xad);
spi_off;
delay_2;

//write to the fifo ctl//
spi_on;
write_byte(0x38,0x80);
spi_off;
delay_2;

// make sure write worked//
spi_on;
fifo = read_byte(0xb8);
spi_off;
delay_2;

// Write 1 to Thresh Tap//
spi_on;
write_byte(0x1d,0x01);
spi_off;
delay_2;

// Write 625us to DUR//
spi_on;
write_byte(0x21,0x01);
spi_off;
delay_2;

// Select z as tap axis//
spi_on;
write_byte(0x2a,0x01);
spi_off;
delay_2;

// Enable the single tap int//
spi_on;
write_byte(0x2e,0x40);
spi_off;
delay_2;

P1REN |= BIT2; // Enable pull up/down resistor
P1OUT &= ~BIT2; // pull down the pin

P1IFG &= ~BIT2; // clear the Int. flag
P1IE |= BIT2; // Enable the Int.
P1IES &= ~BIT2; // Low to high transition

__bis_SR_register(GIE); // Enter interrupt

for(;;); // Infinite For loop
}

char read_byte(char byte)
{

IFG2 &= ~UCB0TXIFG;
wait_tm;
UCB0TXBUF = byte; // Adress to be read
wait_tm; // Transmission Done?
UCB0TXBUF = 0xff; // Dummy write
wait_tm;
return UCB0RXBUF;
}
void get_allaxis(char mbyte)
{

IFG2 &= ~UCB0TXIFG;
wait_tm;
UCB0TXBUF = mbyte; // Starting Adress to be read
wait_tm; // Transmission Done?
UCB0TXBUF = 0xff; // Dummy write
wait_tm;
x0 = UCB0RXBUF;
UCB0TXBUF = 0xff;
wait_tm;
x1 = UCB0RXBUF;
UCB0TXBUF = 0xff;
wait_tm;
y0 = UCB0RXBUF;
UCB0TXBUF = 0xff;
wait_tm;
y1 = UCB0RXBUF;
UCB0TXBUF = 0xff;
wait_tm;
z0 = UCB0RXBUF;
UCB0TXBUF = 0xff;
wait_tm;
z1 = UCB0RXBUF;
}

void write_byte(char addr,char data)
{

wait_tm;
IFG2 &= ~UCB0TXIFG;
UCB0TXBUF = addr; // Read Dev ID
wait_tm; // Transmission Done?
UCB0TXBUF = data; // write
wait_tm;

}

// Port 1 GPIO interrupt service routine
#pragma vector = PORT1_VECTOR
__interrupt void port_1 (void)
{
P1IFG &= ~BIT2; // clear the Int. flag

// read the int source to clear the flag//
spi_on;
ints = read_byte(0xb0);
spi_off;
delay_2;

tick++;
__bis_SR_register(GIE); // Enter interrupt

// read all the axis//
for(;;)
{
spi_on;
delay_4;
get_allaxis(0xf2);
spi_off;
delay_4;

}
}