D435i IMU calibration script

[doronhi]

python.cpp: Add binding of motion_frame.

[barnjamin]

will this be made public?

[dorodnic]

We usually do not release internal design documents directly. These get translated to white-papers and published on realsense.intel.com but it takes long time.
However, most of the information is already public inside ds5-motion.cpp.
The relevant table is structured this way:

This specific table is completely ignored by the firmware. If the calibration tool uses above table format, librealsense will automatically pick-up the values and apply them to the raw IMU data. In this case the calibration tool is this python script with linear regression along 6 known orientations.

Advanced user could implement a completely different calibration method and persist the calibration results on the device. In this case, librealsense will simply ignore it and pass raw IMU data to the application.

[barnjamin]

Awesome, thanks for the insight. Looking forward to trying this out.

[ev-mp]

coefficients,...
used (xor) applied

[doronhi]

@ev-mp
Thanks. Fixed.

[barnjamin]

Using Anaconda Python3 distribution I had to make a couple modifications to the script for it to complete.

I'm not sure if Python3 is officially supported so just including the diff below.

diff --git a/tools/rs-imu-calibration/rs-imu-calibration.py b/tools/rs-imu-calibration/rs-imu-calibration.py
index 0ed3173b..9ff8ec42 100644
--- a/tools/rs-imu-calibration/rs-imu-calibration.py
+++ b/tools/rs-imu-calibration/rs-imu-calibration.py
@@ -193,7 +193,7 @@ class imu_wrapper:
             return False
         self.imu_sensor.stop()
         self.imu_sensor.close()
-        self.imu_sensor.open(active_imu_profiles)
+        self.imu_sensor.open(list(active_imu_profiles))
         self.imu_start_loop_time = time.time()
         self.imu_sensor.start(self.imu_callback)

The above was because the call to dict.values returns a non list type

@@ -354,7 +354,7 @@ def write_eeprom_to_camera(eeprom, serial_no=''):
     DC_MM_EEPROM_SIZE = eeprom.size
     DS5_CMD_LENGTH = 24
 
-    MMEW_Cmd_bytes = '\x14\x00\xab\xcd\x50\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+    MMEW_Cmd_bytes = b'\x14\x00\xab\xcd\x50\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
 
 
     buffer = np.ones([DC_MM_EEPROM_SIZE + DS5_CMD_LENGTH, ], dtype = np.uint8) * 255

The above is because struct.unpack expects a 'bytes-like object'

@@ -491,7 +491,7 @@ def main():
         measurements, gyro = imu.get_measurements(buckets, buckets_labels)
         con_mm = np.concatenate(measurements)
 
-        header = raw_input('\nWould you like to save the raw data? Enter footer for saving files (accel_<footer>.txt and gyro_<footer>.txt)\nEnter nothing to not save raw data to disk. >')
+        header = input('\nWould you like to save the raw data? Enter footer for saving files (accel_<footer>.txt and gyro_<footer>.txt)\nEnter nothing to not save raw data to disk. >')
         if header:
             accel_file = 'accel_%s.txt' % header
             gyro_file = 'gyro_%s.txt' % header
@@ -564,7 +564,7 @@ def main():
     with open(os.path.join(directory,"calibration.bin"), 'wb') as outfile:
         outfile.write(eeprom.astype('f').tostring())
 
-    is_write = raw_input('Would you like to write the results to the camera\'s eeprom? (Y/N)')
+    is_write = input('Would you like to write the results to the camera\'s eeprom? (Y/N)')
     is_write = 'Y' in is_write.upper()
     if is_write:
         print('Writing calibration to device.')

raw_input now just input in python3

[dorodnic]

@barnjamin / @doronhi - we might need to add python3 in a separate PR, since I'd like to include this in the upcoming release.