imu-spi.cpp

00001 //
00002 // imu-spi.cpp
00003 //
00004 // copyright 2010 Hugh Shane
00005 //
00006 #include "mbed.h"
00007 #include "imu-spi.h"
00008 
00009 ImuSpi::ImuSpi(void) :
00010     spi(p5, p6, p7), // mosi, miso, sclk
00011     cs(p8), // IMU chip select
00012     reset(p8), // IMU reset. CAUTION! This also resets the altimeter.
00013     diag(p21), // diagnostic output
00014     imuDataReady(p11) // interrupt on IMU data-ready
00015 {
00016     // Setup the spi for 16 bit data, high steady state clock,
00017     // second edge capture, with a 1 MHz clock rate
00018     spi.format(16,3);
00019     spi.frequency(1000000);
00020     
00021     // init the pingpong buffer
00022     pingpong = 0;
00023     
00024     // init the interrupt semaphore
00025     dataReady = false;    
00026     
00027     // interrupt on the falling edge of the IMU data-ready signal
00028     diag = 0;
00029     imuDataReady.fall(this, &ImuSpi::DataReadyISR);
00030     
00031     // init the IMU
00032     InitImu();
00033 
00034 }
00035 
00036 void  ImuSpi::reinitInterrupts(void) {
00037     imuDataReady.fall(this, &ImuSpi::DataReadyISR);
00038 }
00039 
00040 // initialize the IMU
00041 void ImuSpi::InitImu(void) {
00042     // deselect the IMU
00043     cs = 1;
00044     reset = 1;
00045     // perform a hard reset
00046     reset = 0; wait(.1); reset = 1;    
00047     // send initialization commands
00048     Write(0x34, 0x04); // enable active low data ready on DIO1
00049     Write(0x38, 0x00); // Set the FIR filter to its widest possible bandwidth
00050 }
00051 
00052 // read the IMU accelerometer and gyro registers into the pingpong buffer
00053 void ImuSpi::BurstRead(void) {
00054     static int16_t imuRegs[] = {0x04,0x06,0x08,0x0A,0x0C,0x0E,0x3C};
00055     int16_t* wp = GetBufferWritePtr();
00056     Read(imuRegs[0]); // set up the first register read operation
00057     wait(0.000024); // required to meet IMU t(datarate) spec
00058     
00059     // send register read commands & read the registers
00060     for (int i = 1; i <= 6; i++) {
00061         *wp++ = Read(imuRegs[i]);
00062         wait(0.000024);
00063     }
00064     *wp = Read(0); // read the last register output
00065 }
00066 
00067 int16_t ImuSpi::Read(char adr) {
00068     int16_t cmd = 0x3f00 & (adr << 8);
00069     int16_t response;
00070     cs = 0;
00071     response = spi.write(cmd);
00072     cs = 1;
00073     return response;
00074 }
00075 
00076 
00077 void ImuSpi::Write(char adr, char data) {
00078     int16_t cmd = 0x8000 | (adr << 8) | data;
00079     cs = 0;
00080     spi.write(cmd);
00081     cs = 1;
00082 }
00083 
00084 bool ImuSpi::IsDataReady(void) {
00085     if (dataReady == true) {
00086         dataReady = false;
00087         return true;
00088     } else {
00089         return false;
00090     }
00091 }
00092 
00093 void ImuSpi::DataReadyISR(void) {
00094 diag = 1;
00095     TogglePingpong();
00096     dataReady = true;
00097 diag = 0;
00098 }