Add ability for asynchronous IMU calibration

Update calibration example with demo code

Author: sfe-SparkFro

examples/Example3_Calibration/Example3_Calibration.ino

@@ -49,7 +49,23 @@ void setup()
     // it will take 255 samples and wait until done; each sample takes about
     // 2.4ms, so about 612ms total
     myOtos.calibrateImu();
-    // myOtos.calibrateImu(255, true); // Or specify samples and whether to wait
+
+    // Alternatively, you can specify the number of samples and whether to wait
+    // until it's done. If you don't want to wait, you can asynchronously check
+    // how many samples remain with the code below. Once zero samples remain,
+    // the calibration is done!
+    // myOtos.calibrateImu(255, false);
+    // bool done = false;
+    // while(done == false)
+    // {
+    //     // Check how many samples remain
+    //     uint8_t samplesRemaining;
+    //     myOtos.getImuCalibrationProgress(samplesRemaining);
+
+    //     // If 0 samples remain, the calibration is done
+    //     if(samplesRemaining == 0)
+    //         done = true;
+    // }
 
     // Here we can set the linear and angular scalars, which can compensate for
     // scaling issues with the sensor measurements. Note that as of firmware

src/sfeQwiicOtos.cpp

@@ -110,6 +110,9 @@ sfeTkError_t sfeQwiicOtos::calibrateImu(uint8_t numSamples, bool waitUntilDone)
     if(err != kSTkErrOk)
         return err;
 
+    // Wait 1 sample period (2.4ms) to ensure the register updates
+    delayMs(3);
+    
     // Do we need to wait until the calibration finishes?
     if(!waitUntilDone)
         return kSTkErrOk;
@@ -119,11 +122,6 @@ sfeTkError_t sfeQwiicOtos::calibrateImu(uint8_t numSamples, bool waitUntilDone)
     // of read attempts
     for(uint8_t numAttempts = numSamples; numAttempts > 0; numAttempts--)
     {
-        // Give a short delay between reads. As of firmware v1.0, samples take
-        // 2.4ms each, so 3ms should guarantee the next sample is done. This
-        // also ensures the max attempts is not exceeded in normal operation
-        delayMs(3);
-
         // Read the gryo calibration register value
         uint8_t calibrationValue;
         err = _commBus->readRegisterByte(kRegImuCalib, calibrationValue);
@@ -133,12 +131,23 @@ sfeTkError_t sfeQwiicOtos::calibrateImu(uint8_t numSamples, bool waitUntilDone)
         // Check if calibration is done
         if(calibrationValue == 0)
             return kSTkErrOk;
+
+        // Give a short delay between reads. As of firmware v1.0, samples take
+        // 2.4ms each, so 3ms should guarantee the next sample is done. This
+        // also ensures the max attempts is not exceeded in normal operation
+        delayMs(3);
     }
 
     // Max number of attempts reached, calibration failed
     return kSTkErrFail;
 }
 
+sfeTkError_t sfeQwiicOtos::getImuCalibrationProgress(uint8_t &numSamples)
+{
+    // Read the IMU calibration register
+    return _commBus->readRegisterByte(kRegImuCalib, numSamples);
+}
+
 sfe_otos_linear_unit_t sfeQwiicOtos::getLinearUnit()
 {
     return _linearUnit;

src/sfeQwiicOtos.h

@@ -102,6 +102,8 @@ class sfeQwiicOtos
 
     sfeTkError_t calibrateImu(uint8_t numSamples = 255, bool waitUntilDone = true);
 
+    sfeTkError_t getImuCalibrationProgress(uint8_t &numSamples);
+
     sfe_otos_linear_unit_t getLinearUnit();
 
     void setLinearUnit(sfe_otos_linear_unit_t unit);