main.cpp

00001 #include "mbed.h"
00002 //////////////////////////////////////////////////
00003 // Testing AS5510 sensor with K22F              //
00004 // test results are sent to  Tera Term          //
00005 // I2C frequency set @ 400kHz                   //
00006 //                                              //
00007 // Note 1)                                      //
00008 // I2C address 0x1C is used by FXOS8700CQ       //
00009 // 3-axis accelerometer and 3-axis magetometer  //
00010 //                                              //
00011 // Note 2)                                      //
00012 // Without magnet present the AS5510 sensor is  //
00013 // expected to output a value of approx 511     //
00014 // (1023/2= 511                                 //
00015 //                                              //
00016 // Note 3)                                      //
00017 // Lateral Movement of a simple 2-pole magnet.  //
00018 // Magnet size diameter 1mm length 2mm          //
00019 // Distance to sensor approx 0.8mm              //
00020 // Output 10bit resolution                      //
00021 //////////////////////////////////////////////////
00022 Serial pc(USBTX, USBRX);                // tx, rx
00023 I2C i2c(PTB3, PTB2);                    // SDA, SCL (for K22F)
00024 
00025 const int i2c_slave_addr1 =  0x56;    // sensor AS5510 number 1 (7 bits), 0x56 or 0x57
00026 const int i2c_slave_addr2 =  0x57;    // sensor AS5510 number 2 (7 bits), 0x56 or 0x57
00027 
00028 //--- public functions---
00029 void init_as5510(int);
00030 void read_field(int);
00031 int offset_comp(int);
00032 void look_for_hardware_i2c(void);
00033 
00034 
00035 int main()
00036 {
00037     i2c.frequency(400 * 1000);          // 0.4 mHz
00038     wait_ms(2);                         // Power Up wait
00039 
00040     look_for_hardware_i2c();            // Hardware present ?
00041     init_as5510(i2c_slave_addr1);       // Initialize
00042     init_as5510(i2c_slave_addr2);       // Initialize
00043 
00044     //----------Setup register----------------------
00045     while (!offset_comp(i2c_slave_addr1));
00046     while (!offset_comp(i2c_slave_addr2));
00047     pc.printf("Offset compensation process is completed \r\n");
00048 
00049     //----------Get the results----------------------
00050     while (true) {
00051         read_field(i2c_slave_addr1);     // Read magnetic Field sensor #1
00052         read_field(i2c_slave_addr2);     // Read magnetic Field sensor #2
00053     }
00054 }
00055 
00056 
00057 void look_for_hardware_i2c()
00058 {
00059     pc.printf("\r\n\n\n");
00060     pc.printf("Note I2C address 0x1C used by FXOS8700CQ 3-axis accelerometer and 3-axis magetometer\r\n");
00061     pc.printf("Start hardware search..... \r\n");
00062 
00063     int count = 0;
00064     for (int address=12; address<256; address+=2) {
00065         if (!i2c.write(address, NULL, 0)) {         // 0 returned is OK
00066             pc.printf(" - I2C device found at address 0x%02X\n\r", address >>1);
00067             count++;
00068         }
00069     }
00070     pc.printf("%d devices found \n\r", count);
00071 }
00072 
00073 void init_as5510(int i2c_address)
00074 {
00075     int i2c_adrs=0;
00076     char idata[2];
00077     int result=0;
00078 
00079     pc.printf("\r\n");
00080     pc.printf("Start AS5510 init.. \r\n");
00081 
00082     i2c_adrs= (i2c_address << 1);                   // AS5510 Slave address lsb= 0 for write
00083 
00084     //---------- Magnet selection --------------------------------
00085     //----0x00= <50mT-----------Strong magnet
00086     //----0x01= <25mT
00087     //----0x02= <18.7mT
00088     //----0x03= <12.5mT---------Weak magnet
00089     //-----------------------------------------------------------
00090     idata[0]=0x0B;                                  // Register for Sensitivity
00091     idata[1]=0x00;                                  // Byte
00092     result= i2c.write(i2c_adrs, idata, 2, 0);       // Now write_sensitivity
00093     if (result != 0) pc.printf("No ACK bit! (09)\n\r");
00094 
00095     //----------- Operation mode selection------------------------
00096     idata[0]=0x02;                                  // 0x02 address setup register for operation, speed, polarity
00097     idata[1]=0x04;                                  // Normal Operation, Slow mode (1), NORMAL Polarity (0), Power Up (0)
00098     result= i2c.write(i2c_adrs, idata, 2, 0);       // Now write_operation
00099     if (result != 0) pc.printf("No ACK bit! (11)\n\r");
00100 
00101     pc.printf("AS5510 init done\r\n");
00102 }
00103 
00104 
00105 int offset_comp(int i2c_address)
00106 {
00107     int adrss=0;
00108     int oresult=0;
00109     char off_data[2];
00110     int ocf_done=0;
00111 
00112     // First, now Write pointer to register 0x00----------------------------
00113     adrss= (i2c_address << 1);                  // AS5510 Slave address lsb= 0 for write
00114     oresult= i2c.write(adrss, 0x00, 1, 0);      // write one byte
00115     if (oresult != 0) pc.printf("No ACK bit! (33)\n\r");
00116 
00117     // Second, now Read register 0x00 and 0x01--------------------------------
00118     memset(off_data, 0, sizeof(off_data));
00119     adrss= (i2c_address << 1) | 0x01;           // AS5510 address lsb= 1 for read
00120     oresult= i2c.read(adrss, off_data, 2, 0);   // read two bytes
00121 
00122     // Now analyse register 0x01 ----------------------------------------------
00123     ocf_done= off_data[1] & 0x08;               // mask off bits, 1= done
00124     if (ocf_done== 0)  return(0);               // return(0)= compensation process is pending
00125     else return(1);                             // return(1)= compensation process is completed
00126 }
00127 
00128 
00129 void read_field(int i2c_address)
00130 {
00131     int adr=0;
00132     char rx_data[2];
00133     int rresult=0;
00134     char lsb, msb;
00135     unsigned int value;
00136 
00137     // First, now Write pointer to register 0x00----------------------------
00138     adr= (i2c_address << 1);                        // AS5510 address lsb= 0 for write
00139     rresult= i2c.write(adr, 0x00, 1, 0);            // write one byte to register 0x00 for magnetic field strength
00140     if (rresult != 0) pc.printf("No ACK bit! (22)\n\r");
00141 
00142     // Second, now Read register 0x00 and 0x01--------------------------------
00143     memset(rx_data, 0, sizeof(rx_data));
00144     adr= (i2c_address << 1) | 0x01;                 // AS5510 address lsb= 1 for read
00145     rresult= i2c.read(adr, rx_data, 2, 0);          // read two bytes
00146 
00147 
00148     // Now analyse register 0x01 ----------------------------------------------
00149     lsb= rx_data[0];                                // get LSB
00150     msb= rx_data[1]&0x03;                           // need only 2 low bits og MSB
00151     value = ((msb & 0x03)<<8) + lsb;
00152     pc.printf("I2C adres= 0x%02X, Magnetic Field => msb= 0x%02X, lsb= 0x%02X, decimal 10-bit value = %u \r\n ", i2c_address, rx_data[0],rx_data[1], value);
00153 }
00154 
00155