A class to receive data from the SparkFun 9DOF Razor IMU. It can be easily adapted to work with IMUs with different data formats.
Diff: imu.cpp
- Revision:
- 2:d8b182fbe018
- Child:
- 3:f04d3d10d518
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/imu.cpp Fri Nov 04 22:24:02 2011 +0000 @@ -0,0 +1,174 @@ +#include "mbed.h" +#include "imu.h" + +IMU::IMU(int baud, PinName tx, PinName rx, Serial* pc){ + p_pc = pc; + p_pc->printf("Initializing IMU...\n"); + p_device = new Serial(tx, rx); + p_device->baud(baud); + p_device->format(8, Serial::None, 1); + readable = false; + i_IMU = 0; + accX = accY = accZ = gyrX = gyrY = gyrZ = magX = magY = magZ = 0; + p_device->putc('6'); //Tell the IMU to start sending binary data, if it isn't already +} + +IMU::~IMU() { + if (p_device != NULL){ + delete p_device; //This prevents memory leaks and keeps the port accessible for future use. + } +} + +//Wrapper function to write a character to the IMU +void IMU::putc(char c) { + p_device->putc(c); +} + + +//Wrapper function to attach a callback function to the RX interrupt of the IMU Serial object +void IMU::attach(void (*fptr)(void)) { + p_pc->putc('a'); + p_device->attach(fptr); +} + +//Gets all data from the IMU read buffer. If we should parse, parse. +void IMU::getData() { + readable = false; + //p_pc->printf("HELLO"); + __enable_irq(); + //NVIC_EnableIRQ(UART1_IRQn); + while (p_device->readable()) { + //p_pc->printf("readable"); + // This snippet of code should be run whenever a character can be received from the IMU. + + char data = p_device->getc(); + + // Start of a new set of data. Reset the counter to the first position in the buffer, and start throwing data in there. + if (data == '$') { + i_IMU = 0; + //p_pc->printf("new data\n\r"); + } + // Something went wrong. + else if (i_IMU > 21) { + //p_pc->printf("\t\t\tIMU error.\n\r"); + i_IMU = 21; + } + + // End of the set of data. Parse the buffer + else if (i_IMU == 21 /*&& bufIMU[0] == '$' && bufIMU[20] == '\n' data == '\n' && i_IMU == 19*/) { + parse(); + } + + + bufIMU[i_IMU] = data; + i_IMU++; + //parseNow = (buffer.at(buffer.length() - 1) == '#'); + } +} + +//So negative numbers that are transferred are in twos complement form +// and the compiler seems to like to use things created by bitwise operators +// in unsigned form so all of the bits are switched and we switch it back and center +// it around 512 which we are using as out zero value +inline void IMU::makeCorrect(short* i) { + if ((*i)>>15) *i = 512-(~(*i)); + else *i = 512+*i; +} + +/* +void IMU::attach(void) { + p_device->attach(this->readIMU); +}*/ + +void IMU::parse() { + p_pc->printf("Parsing\n\r"); + + //This should be easier to understand than bitshifts. bufIMU is a pointer (arrays are pointers). + //We offset it to the start of the desired value. We then typecast bufIMU into a short (16 bit). + //This turns bufIMU into a pointer to the desired value. Now we dereference it. + //I'm not sure if we'll still need makeCorrect. + + //Don't use this. It doesn't work. + //Kevin said this didn't work because of endianness. The Cortex M3 has a macro to reverse. + //See http://mbed.org/forum/helloworld/topic/1573/?page=1#comment-7818 + /*accX = *((short*)(bufIMU + 2)); + accY = *((short*)(bufIMU + 4)); + accZ = *((short*)(bufIMU + 6)); + + gyrX = *((short*)(bufIMU + 8)); + gyrY = *((short*)(bufIMU + 10)); + gyrZ = *((short*)(bufIMU + 12)); + + magX = *((short*)(bufIMU + 14)); + magY = *((short*)(bufIMU + 16)); + magZ = *((short*)(bufIMU + 18));*/ + + //bufIMU contains binary data. Each variable sent by the IMU is a 16-bit integer + //broken down into two characters (in bufIMU[]). Here, we reconstitute the original integer by + //left-shifting the first character by 8 bits and ORing it with the second character. + + accX = (bufIMU[1]<<8 | bufIMU[2]); + accY = (bufIMU[3]<<8 | bufIMU[4]); + accZ = (bufIMU[5]<<8 | bufIMU[6]); + + gyrX = (bufIMU[7]<<8 | bufIMU[8]); + gyrY = (bufIMU[9]<<8 | bufIMU[10]); + gyrZ = (bufIMU[11]<<8 | bufIMU[12]); + + magX = (bufIMU[13]<<8 | bufIMU[14]); + magY = (bufIMU[15]<<8 | bufIMU[16]); + magZ = (bufIMU[17]<<8 | bufIMU[18]); + + makeCorrect(&accX); + makeCorrect(&accY); + makeCorrect(&accZ); + + makeCorrect(&gyrX); + makeCorrect(&gyrY); + makeCorrect(&gyrZ); + + makeCorrect(&magX); + makeCorrect(&magY); + makeCorrect(&magZ); + + + //PC.printf("Data: %d, %d, %d, %d, %d, %d, %d, %d, %d\n\r", accX, accY, accZ, gyrX, gyrY, gyrZ, magX, magY, magZ); + + //accX = accY = accZ = gyrX = gyrY = gyrZ = magX = magY = magZ = 0; + + /* + for (int i = 0; i < 21; i++) { + PC.printf("%d ", bufIMU[i]); + } + PC.printf("\n\r"); + */ + //newIMUData = 1; // Update the flag +} + + +//Callback called when there is a character to be read from the IMU +void readIMU() { + imu.readable = true; + __disable_irq(); + //NVIC_DisableIRQ(UART1_IRQn); +} + +int main() { + PC.format(8, Serial::None, 1); + PC.baud(115200); + + for (int i = 0; i < 80; i++) { + PC.putc('-'); + } + PC.printf("\n\r"); + imu.attach(&readIMU); + //imu.p_device->attach(&readIMU); + imu.putc('6'); + while (true){ + if (imu.readable) { + //PC.printf("fun"); + imu.getData(); + PC.printf("Data: %d, %d, %d, %d, %d, %d, %d, %d, %d\n\r", imu.accX, imu.accY, imu.accZ, imu.gyrX, imu.gyrY, imu.gyrZ, imu.magX, imu.magY, imu.magZ); + } + } +} \ No newline at end of file