main.cpp

00001 #include "mbed.h"
00002 #define BMA180_ID       0x00
00003 #define VERSION         0x01
00004 #define ACCXLSB         0x02
00005 #define ACCXMSB         0x03
00006 #define ACCYLSB         0x04
00007 #define ACCYMSB         0x05
00008 #define ACCZLSB         0x06
00009 #define ACCZMSB         0x07
00010 #define CTRL_REG0       0x0D
00011 #define DIS_I2C         0x27    // bit 0 must be 1 for SPI
00012 #define CTRL_REG3       0x21    // bit 1= new_data_int
00013 #define RESET           0x10    // soft reset
00014 
00015 /*-------------Hardware connections-------------
00016 By Gerrit Pathuis (gpa@quicknet.nl)
00017 MBA180 breakour board (sparkfun) is used
00018 VIO----- mbed Vout (3.3 Volt)
00019 SDI----- mbed mosi (p5)
00020 SDO----- mbed miso (p6)
00021 SCK----- mbed sck  (p7)
00022 CS------ mbed (p8)          // chip select
00023 INT----- mbed (p9)          // MBA give a interrupt when ready
00024 GND----- mbed GND (0 Volt)
00025 VDO----- mbed Vout (3.3 Volt)
00026 there are no additional external components used
00027 //----------------------------------------------*/
00028 
00029 SPI spi(p5,p6,p7); //mosi, miso, sclk
00030 DigitalOut cs(p8);
00031 InterruptIn event(p9);
00032 
00033 Serial pc(USBTX, USBRX); // tx, rx
00034 void init_SPI_BMA180(void);
00035 void soft_reset(void);
00036 void trigger(void);
00037 void new_data(void);
00038 void write_bits(char u);
00039 void write_reg(uint8_t address, char data);
00040 char read_reg(uint8_t address);
00041 void disable_int(void);
00042 
00043 struct sample {                 // reserve spave for 1000 samples
00044     signed short x;
00045     signed short y;
00046     signed short z;
00047     signed short t;
00048 } vib[1000+1];
00049 
00050 int sample_cnt;
00051 
00052 int main() {
00053     int pp;
00054     float xx, yy, zz;
00055 
00056     init_SPI_BMA180();          // init the sensor
00057     sample_cnt =0;              // start the counter
00058     pc.printf("Start lurking  ");
00059     while (sample_cnt <50) {
00060         event.rise(&trigger);
00061     }
00062     disable_int();              // switch the BMA180 off
00063     pc.printf("\n\r\nPresent the data\n\r");
00064     for (pp=0; pp<50; pp +=1)  {
00065         // 2^14 = 16384
00066         // Range is +/1 2.0 G versnelling
00067         xx = vib[pp].x/16384.0*4.0;
00068         yy = vib[pp].y/16384.0*4.0;
00069         zz = vib[pp].z/16384.0*4.0;
00070         pc.printf("Sample %2d, Acc X= %0.4f, Y= %0.4f, Z= %0.4f \n\r", pp, xx, yy, zz);
00071     }
00072 }
00073 
00074 void init_SPI_BMA180(void) {
00075     char readVersion, readID;
00076     char byte;
00077     // Setup the spi for 8 bit data, high steady state clock,
00078     // second edge capture, with a 10MHz clock rate
00079 
00080     spi.frequency(10000000);        // 10 mHz page 59 of the BMA180 datasheet
00081     spi.format(8,3);                // Not conform !!! page 58 of the BMA180 datasheet)
00082     wait_ms(100);
00083     readID = read_reg(BMA180_ID);
00084     readVersion = read_reg(VERSION);
00085     pc.printf("\n\r");
00086     if (readID == 3) {
00087         pc.printf("Connected to BMA180\n\r");
00088         pc.printf("BMA180 Version %d\n\r", readVersion);
00089     } else
00090         pc.printf("Sorry not connected to BMA180 !!!\n\r", readID);
00091 
00092     soft_reset();   // to copy EEprom into volatile area
00093 
00094     //---------------------------
00095     byte = read_reg(CTRL_REG0);             // Unlock image writing
00096     byte |= 0x10;                           // Set bit 4
00097     write_reg(CTRL_REG0,byte);              // Have to set ee_w to
00098     //------------------------
00099     byte= read_reg(DIS_I2C);                // read
00100     byte |= 0x01;                           // set bit0 to 1, SPI only
00101     write_reg(DIS_I2C, byte);               // Set spi, disable i2c, page 31
00102     //-------------------------
00103     byte = read_reg(CTRL_REG3);
00104     byte |= 0x02;                           // set bit 1 enable interrupt
00105     byte |= 0x40;                           // set bit 6 slope mode
00106     byte |= 0x80;                           // set bit 6 slope alert
00107     write_reg(CTRL_REG3,byte);              //
00108     pc.printf("Enable interrupt bis is set ");
00109     //------------------------------
00110     byte = read_reg(CTRL_REG0);             // Lock image writing
00111     byte &= 0xEF;                           // REset  bit 4
00112     write_reg(CTRL_REG0,byte);              // Have to set ee_w to
00113     //-------------------------------------------------------------------------------------
00114     pc.printf("\n\rBMA init done    \n\r");
00115 }
00116 
00117 void soft_reset(void) {
00118     // Write a soft reset
00119     // to copy EEprom into volatile area, see mid page 22
00120     write_reg(RESET, 0xB6);             // page 48
00121     wait_ms(10);                        // wait 10 ms, see page 49
00122     pc.printf("Soft reset, EEPROM copied    \n\r");
00123 }
00124 
00125 //-----------------READ OUT the X-Y-Z values---------------
00126 void trigger(void) {
00127     char x_lsb, x_msb;
00128     char y_lsb, y_msb;
00129     char z_lsb, z_msb;
00130     signed short ax, ay, az;
00131 
00132     //------------X----------------
00133     x_lsb = read_reg(ACCXLSB);
00134     x_msb = read_reg(ACCXMSB);
00135     ax = (x_msb << 8) |  x_lsb ;   // combineer msb en lsb
00136     ax = ax >> 2;                  // Get rid of two non-value bits in LSB
00137     //------------Y----------------
00138     y_lsb = read_reg(ACCYLSB);
00139     y_msb = read_reg(ACCYMSB);
00140     ay = (y_msb << 8) | y_lsb;     // combineer msb en lsb
00141     ay = ay >> 2;                  // Get rid of two non-value bits in LSB
00142     //------------Z----------------
00143     z_lsb = read_reg(ACCZLSB);
00144     z_msb = read_reg(ACCZMSB);
00145     az = (z_msb << 8) |  z_lsb;    //  combineer msb en lsb
00146     az = az >> 2;                  // Get rid of two non-value bits in LSB
00147 
00148     //----------shift into the array---------------------
00149     vib[sample_cnt].x= ax;
00150     vib[sample_cnt].y= ay;
00151     vib[sample_cnt].z= az;
00152     //---------counter------------
00153     sample_cnt += 1;
00154 }
00155 
00156 void write_reg(uint8_t address, char data) {
00157     address &= 0x7F;                        //Force a write (bit 7=0)
00158     cs=0;                                   //Select SPI device
00159     wait_us(2);
00160     spi.write(address);                     //Send register location
00161     wait_us(2);
00162     spi.write(data);                        //Send value to record into register
00163     wait_us(2);
00164     cs=1;
00165     wait_us(2);
00166 }
00167 
00168 char read_reg(uint8_t address) {
00169     char byte;
00170     address |= 0x80;                        //Force a read (bit 7=1)
00171     cs=0;
00172     wait_us(2);                             //Select SPI device
00173     spi.write(address);                     //Send register location
00174     wait_us(2);
00175     byte=spi.write(0xFF);                   //Get the data
00176     wait_us(2);
00177     cs=1;
00178     wait_us(2);
00179     return byte;
00180 }
00181 
00182 void disable_int(void) {
00183     char byte;
00184     byte = read_reg(CTRL_REG0);             // Unlock image writing
00185     byte |= 0x10;                           // Set bit 4
00186     write_reg(CTRL_REG0,byte);              // Have to set ee_w to
00187     //-------------------------
00188     byte = read_reg(CTRL_REG3);
00189     byte &= 0xFD;                           // REset bit 1 enable interrupt
00190     write_reg(CTRL_REG3,byte);              //
00191     pc.printf("\n\rDisable interrupt bis is set ");
00192     //------------------------------
00193     byte = read_reg(CTRL_REG0);             // Lock image writing
00194     byte &= 0xEF;                           // REset  bit 4
00195     write_reg(CTRL_REG0,byte);              // Have to set ee_w to
00196     pc.printf("\n\rMBA180 in now switched off ");
00197 }
00198