Hello everyone,
I am currently planning to build a completely untethered calibration cube (an icosahedron jig) for IMU and magnetometer calibration, as you can see in the images above. I am also incorporating a SPAD sensor to obtain the floor’s normal vector, which will serve as the ground truth (up vector) for the accelerometer. I plan to mount all the components using hex standoffs.
My main board is the SparkFun ESP32 Thing Plus (USB-C), and I’m gathering data using the following Qwiic sensors: the TMF8821 (SPAD) and the Qwiic 9DoF (ISM330DHCX, MMC5983MA). I need to log the data without any USB cables attached, as the physical tension from the cable ruins the static assumptions needed for my calibration.
According to the SparkFun Hookup Guide, the USB-C variant of the ESP32 Thing Plus features an included SD card slot. The guide also notes that the board retains the standard 2-pin JST battery connector and integrates a battery fuel gauge. Based on this, I plan to run the system entirely on a 3.7V Li-Po battery and log my sensor data directly to a MicroSD card.
Before I make a purchase, I would love some specific hardware recommendations from the community:
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3.7V Li-Po Battery: Could you recommend a specific capacity (mAh) or a SparkFun part number? It needs to be relatively compact to fit inside a 3D-printed jig, but it also needs to reliably power the ESP32 and the $I^2C$ sensors for at least a couple of hours of continuous logging.
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MicroSD Card: Are there any specific capacities (e.g., 8GB, 16GB, 32GB) or speed classes that are known to work best with the ESP32 Thing Plus? I want to avoid any compatibility or SPI bottleneck issues while continuously writing data.
Ideally, both the battery and the MicroSD card setup should easily integrate into an extended version of the 3D-printed structure shown below.
Thanks in advance for your help!
