Diff: IMU/IMU.cpp

Revision:

66:0f20870117b7

Child:

74:d281aaef9766

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/IMU/IMU.cpp	Tue Jun 19 20:14:23 2018 +0000
@@ -0,0 +1,244 @@
+#include "IMU.h"
+
+IMU::IMU(PinName Tx, PinName Rx): 
+    _rs232(Tx,Rx)
+{
+}
+
+void IMU::initialize() {
+    //set up the spi bus and frequency
+    _rs232.baud(115200);
+
+    // initialize the processing state machine
+    state = SYNC0; 
+    
+    // initialize to zeros
+    euler[0] = 0.0;
+    euler[1] = 0.0;
+    euler[2] = 0.0;
+    
+    // initialize to zeros
+    latLonAlt[0] = 0.0;
+    latLonAlt[1] = 0.0;
+    latLonAlt[2] = 0.0;
+    
+    // initialize to no GNSS fix
+    is2dFixValid = false;
+    is3dFixValid = false;
+    numSV = 0;
+}
+
+// this stops an interval timer trigger of the IMU update function
+void IMU::start() {
+    interval.attach(this, &IMU::update, .05);  //this should be a 1 Hz sample rate
+}
+
+// this stops the interval timer trigger of the IMU update function
+void IMU::stop() {
+    interval.detach();
+}
+
+void IMU::runIMU() {
+    update();
+}
+
+// updated the imu update function with a state machine that doesn't hang if no data is present
+void IMU::update() {
+    
+//    // DEBUGGING an example packet
+//    Serial pc(USBTX, USBRX);
+//    //char data[20] = {0x75,0x65,0x80,0x0E,0x0E,0x04,0x3E,0x7A,0x63,0xA0,0xBB,0x8E,0x3B,0x29,0x7F,0xE5,0xBF,0x7F,0x84,0xEE}; // 3d accel
+//    char data[20] = {0x75,0x65,0x80,0x0E,0x0E,0x0C,0xBA,0xE3,0xED,0x9B,0x3C,0x7D,0x6D,0xDF,0xBF,0x85,0x5C,0xF5,0x41,0xBB}; // euler cf
+//    for (int j=0; j<20; j++) {
+        //byte = data[j];
+        
+    while (_rs232.readable()) {
+        // read a single byte
+        byte = _rs232.getc();
+        
+        // state machine to process byte-by-byte
+        switch (state) {
+        case SYNC0 : 
+            if (byte == 0x75) {
+                packet[0] = byte; // save into the packet
+                state = SYNC1;
+            }
+            break;
+            
+        case SYNC1 :
+            if (byte == 0x65) {
+                packet[1] = byte; // save into the packet
+                state = SET;
+            }
+            else {
+                state = SYNC0;
+            }
+            break;
+            
+        case SET :
+            descriptor = byte; // save descriptor set
+            packet[2] = byte; // save into the packet
+            state = LEN;
+            break;
+            
+        case LEN :
+            len = byte; // save payload length
+            packet[3] = byte; // save into the packet
+            state = PAY;
+            i = 0; // reset payload field length counter
+            break;
+            
+        case PAY :
+            if (i < len) { // keep adding until get all the payload length
+                packet[4+i] = byte; // add byte to the packet, skipping over the header 4-bytes
+                i++; // increment payload counter
+            }
+            else {
+                state = CRC0;
+            }
+            if (i >= len) { // not an elseif, since we want to escape when i==len
+                state = CRC0;
+            }
+            break;
+            
+        case CRC0 :
+            crc0 = byte; // save the msb of the checksum
+            state = CRC1;
+            break;
+            
+        case CRC1 :
+            crc1 = byte; // save the lsb of the checksum
+            checksum = ((unsigned int)crc0 << 8) + (unsigned int)crc1; // make checksum into a uint16
+            if (checksum == calcChecksum(packet, len+4)) { // passed checksum, wahoo!
+                processPayload(descriptor, packet[4], &packet[4]); // process the payload part of the packet, starting at byte 4
+            }
+            state = SYNC0; // reset to SYNC0 state
+            break;
+
+        default :
+            state = SYNC0;
+        }
+    }
+    return;
+}
+
+void IMU::processPayload(char descriptor, char length, unsigned char * payload) {
+    if (descriptor == IMU_DATA_SET) { // find an IMU data descriptor set
+        if (length > 2) { // make sure there are at least two bytes to see the field descriptor
+            if (payload[1] == EULER_CF_DESCRIPTOR) { // find an euler CF field descriptor
+                processEulerCfPacket(length, payload);
+            }
+        }
+    }
+    else if (descriptor == GNSS_DATA_SET) { // find a GNSS data descriptor set
+        if (length > 2) { // make sure there are at least two bytes to see the field descriptor
+            if (payload[1] == LLH_POSITION_DESCRIPTOR) { // find a lat-lon-alt field descriptor
+                processLatLonAltPacket(length, payload);
+            }
+            else if (payload[1] == GNSS_FIX_INFO_DESCRIPTOR) { // find a gnss fix field descriptor
+                processGnssFixInformation(length, payload);
+            }
+        }
+    }
+}
+
+void IMU::processEulerCfPacket(char length, unsigned char * payload) {
+    if (length >= EULER_CF_LENGTH) { // make sure correct field length
+        if (payload[0] == EULER_CF_LENGTH) { // make sure field length is as expected
+            euler[0] = floatFromChar(&payload[ROLL_OFFSET+2])*180/_PI;  // roll Euler angle convert in degrees
+            euler[1] = floatFromChar(&payload[PITCH_OFFSET+2])*180/_PI; // pitch Euler angle convert in degrees
+            euler[2] = floatFromChar(&payload[YAW_OFFSET+2])*180/_PI;   // yaw Euler angle convert in degrees
+        }
+    }
+}
+
+void IMU::processLatLonAltPacket(char length, unsigned char * payload) {
+    if (length >= LLH_POSITION_LENGTH) { // make sure correct field length
+        if (payload[0] == LLH_POSITION_LENGTH) { // make sure field length is as expected
+            latLonAlt[0] = doubleFromChar(&payload[LATITUDE_OFFSET+2]);   // latitude in decimal degrees
+            latLonAlt[1] = doubleFromChar(&payload[LONGITUDE_OFFSET+2]);  // longitude in decimal degrees
+            latLonAlt[2] = doubleFromChar(&payload[HEIGHT_MSL_OFFSET+2]); // altitude above mean sea level in meters
+        }
+    }
+}
+
+void IMU::processGnssFixInformation(char length, unsigned char * payload) {
+    if (length >= GNSS_FIX_INFO_LENGTH) { // make sure field length is as expected
+        if (payload[0] == GNSS_FIX_INFO_LENGTH) { // make sure field length is as expected
+            is2dFixValid = char(payload[FIX_TYPE_OFFSET+2]) & 0x01; // bitand on LSB to see 2d fix flag
+            is3dFixValid = char(payload[FIX_TYPE_OFFSET+2]) & 0x02; // bitand on LSB to see 3d fix flag
+            numSV = char(payload[NUM_SV_OFFSET+2]); // number of GNSS satellite vehicles
+        }
+    }
+}
+
+float IMU::floatFromChar(unsigned char * value) {
+    unsigned char temp[4];
+    temp[0] = value[3];
+    temp[1] = value[2];
+    temp[2] = value[1];
+    temp[3] = value[0];
+    return *(float *) temp;
+}
+
+double IMU::doubleFromChar(unsigned char * value) {
+    unsigned char temp[8];
+    temp[0] = value[7];
+    temp[1] = value[6];
+    temp[2] = value[5];
+    temp[3] = value[4];
+    temp[4] = value[3];
+    temp[5] = value[2];
+    temp[6] = value[1];
+    temp[7] = value[0];
+    return *(double *) temp;
+}
+
+float IMU::getRoll() {
+    return euler[0];
+}
+
+float IMU::getPitch() {
+    return euler[1];
+}
+
+float IMU::getHeading() {
+    return euler[2];
+}
+
+bool IMU::getIsValid2dFix() {
+    return is2dFixValid;   
+}
+
+bool IMU::getIsValid3dFix() {
+    return is3dFixValid;
+}
+
+char IMU::getNumSV() {
+    return numSV;
+}
+
+double IMU::getLatitude() {
+    return latLonAlt[0];
+}
+
+double IMU::getLongitude() {
+    return latLonAlt[1];
+}
+
+double IMU::getAltitudeMSL() {
+    return latLonAlt[2];
+}
+
+unsigned int IMU::calcChecksum(unsigned char * mip_packet, char checksum_range) {
+    unsigned char checksum_byte1 = 0;
+    unsigned char checksum_byte2 = 0;
+    unsigned int myChecksum = 0;
+    
+    for (int i=0; i<checksum_range; i++) {
+        checksum_byte1 += mip_packet[i];
+        checksum_byte2 += checksum_byte1;
+    }
+    myChecksum = ((unsigned int)checksum_byte1 << 8) + (unsigned int)checksum_byte2;
+    return myChecksum;
+}
\ No newline at end of file