SensiML_xG24_IMU_Capture
Summary
This project uses the EFR32xG24 Dev Kit Board and onboard IMU to measure accelerometer and gyroscope data and transmit the measurement data via serial UART for consumption by SensiML's Data Capture Lab. The example project uses the I/O Stream service along with IMU component drivers running in a bare-metal configuration. Sensor data from the ICM-20648 IMU is transferred over virtual COM port (VCOM) at 921600 baud. The sensor data output data rate is configured at 102.3Hz.
Software Components used: IMU - Inertial Measurement Unit, Simple LED, IO Stream: USART, Sleeptimer
Gecko SDK version
v4.02
Hardware Required
-
One EFR32xG24 Dev Kit Board (Link currently unavailable)
-
One micro USB cable
Setup
Import the included .sls file to Studio then build and flash the project to the SLTB004A development kit. In Simplicity Studio select "File->Import" and navigate to the directory with the .sls project file. The project is built with relative paths to the STUDIO_SDK_LOC variable which was defined as
C:\SiliconLabs\SimplicityStudio\v5\developer\sdks\gecko_sdk_suite\v4.0
In Simplicity Studio, under the Debug Adapters window, right-click on the EFR32xG24 Dev Kit Board and select "Launch console..." from the drop-down menu. In the Adapter Console window, select the "Admin" tab and type "serial vcom config speed 921600" into the terminal input. This will modify the VCOM baudrate to match the application settings. If making any changes to the USART baudrate, the baudrate change must also be modified in the VCOM debug adapter settings.
How the Project Works
The application uses the process-action bare-metal project configuration model. First, the IO Stream/USART are configured for 8 bit, no parity, 1 stop bit, and 921600 baudrate. A periodic sleep timer is also configured with 1 second interrupt. Within the application's process actions, the serial input is monitored for a connection command expected from SensiML's Data Capture Lab (DCL). A JSON configuration packet is sent via USART/VCOM to the PC once per second (via sleep timer) until the connection command is received, at which point the application halts monitoring the serial input and sending configuration information and the IMU is initialized and motion data sent to PC at the specified data rate (default setting is 102.3 Hz). The onboard LEDs are also used to indicate that the application is running (blinking green LED at 2 Hz) and when the application is waiting for the connection command (solid red LED). Once connected, the red LED will turn off. Upon disconnecting from SensiML, the red LED will be turned on again and the device will resume sending configuration packets. The device can be reconnected without a reset.
The output data rate is hard-coded in the application in "app_sensor_imu.h" defined as ACCEL_GYRO_DEFAULT_ODR (line 41) using the enumeration "accel_gyro_odt_t" starting at line 25. A subset of IMU data sampling rates is made available through this enumeration. For more information, see the ICM-20648 datasheet available here - https://invensense.tdk.com/download-pdf/icm-20648-datasheet/
The sensor sampling rate can be modified by changing the #define ACCEL_GYRO_DEFAULT_ODR in the source. When doing so, it is important for the user to also configure/re-configure the sensor settings within SensiML's Data Capture Lab to reflect these changes. The configurations must match for the data acquisition to operate correctly.
Note: The EFR32xG24 Dev Kit Board must be placed on a stable surface during initialization as the IMU undergoes a calibration routine at this time.
.sls Projects Used
SensiML_xG24_IMU_Capture.sls