--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bma180.c	Wed Sep 19 22:40:49 2012 +0800
@@ -0,0 +1,146 @@
+#include <avr/io.h>
+#include <util/delay.h>
+
+#include "bma180.h"
+#include "bma180_internal.h"
+
+static void 
+bma180_init_SPI(void)
+{
+    //make SPI master
+    //SCL idle high, sample data on rising edge
+    //Fosc/4 is SPI frequency
+    //enable SPI
+    SPCR = _BV(MSTR) | _BV(SPE) | _BV(CPHA) | _BV(CPOL);
+}
+
+static char 
+bma180_rxdata(void)
+{
+    //while((SPSR&0x80) == 0x80);
+    SPDR = 0x55;
+    while((SPSR&0x80) == 0x00);
+
+    return SPDR;
+}
+
+static void 
+bma180_txdata(char data)
+{
+    //while((SPSR&0x80) == 0x80);
+    SPDR = data;
+    while((SPSR&0x80) == 0x00);
+}
+
+static void 
+bma180_write(uint8_t address, char data)
+{
+    //write any data byte to any single address
+    //adds a 0 to the MSB of the address byte (WRITE mode)
+
+    address &= 0x7F;    
+
+    //printf("\nWriting 0x%x to 0x%x\n", data, address);
+
+    BMA180_CS_PORT &= ~_BV(BMA180_CS_PIN);
+    _delay_ms(1);
+    bma180_txdata(address);
+    _delay_ms(1);
+    bma180_txdata(data);
+    _delay_ms(1);
+    BMA180_CS_PORT |= _BV(BMA180_CS_PIN);
+}
+
+static char 
+bma180_read(uint8_t address)
+{
+    //returns the contents of any 1 byte register from any address
+    //sets the MSB for every address byte (READ mode)
+
+    char byte;
+
+    address |= 0x80;
+
+    BMA180_CS_PORT &= ~_BV(BMA180_CS_PIN);
+    bma180_txdata(address);
+    byte = bma180_rxdata();
+    BMA180_CS_PORT |= _BV(BMA180_CS_PIN);
+
+    return byte;
+}
+
+static int 
+bma180_set_config(uint8_t range, uint8_t bw)
+{
+    char temp, temp1;
+    
+    // if connected correctly, ID register should be 3
+    if(bma180_read(ID) != 3)
+        return -1;
+        
+
+    // Set ee_w bit
+    temp = bma180_read(CTRLREG0);
+    temp |= 0x10;
+    bma180_write(CTRLREG0, temp);  // Have to set ee_w to write any other registers
+
+    // Set BW
+    temp = bma180_read(BWTCS);
+    temp1 = bw;
+    temp1 = temp1<<4;
+    temp &= (~BWMASK);
+    temp |= temp1;
+    bma180_write(BWTCS, temp);     // Keep tcs<3:0> in BWTCS, but write new BW
+
+    // Set Range
+    temp = bma180_read(OLSB1);
+    temp1 = range;
+    temp1 = (temp1<<RANGESHIFT);
+    temp &= (~RANGEMASK);
+    temp |= temp1;
+    bma180_write(OLSB1, temp); //Write new range data, keep other bits the same
+    
+    return 0;
+}
+
+void
+bma180_init(uint8_t range, uint8_t bw)
+{
+    bma180_init_SPI();
+
+    // CS output 
+    // XXX checkme, sample code has the opposite?
+    BMA180_CS_DDR |= _BV(BMA180_CS_PIN);
+
+    bma180_set_config(range, bw);
+
+}
+
+static uint16_t 
+bma_get_reading_n(uint8_t reg_lsb, uint8_t reg_msb)
+{
+    uint16_t ret;
+    uint8_t val = 0;
+    while (val != 1)
+    {
+        val = bma180_read(reg_lsb) & 0x01;
+    }
+    val = bma180_read(reg_msb);
+    ret = val << 8;
+
+    val = bma180_read(reg_lsb);
+    ret |= val;
+    // low bits aren't the reading
+    ret >>= 2;
+    return ret;
+}
+
+void
+bma180_get_reading(uint16_t *x, uint16_t *y, uint16_t *z, uint8_t *temperature)
+{
+    *x = bma_get_reading_n(ACCXLSB, ACCXMSB);
+    *y = bma_get_reading_n(ACCYLSB, ACCYMSB);
+    *z = bma_get_reading_n(ACCZLSB, ACCZMSB);
+
+    *temperature = bma180_read(TEMPERATURE);
+}