OK before we continue, we have to check that we are able to store calibration either in the EEPROM (ATmega328, 'm32u4, 'm2560, ESP8266, ESP32) or (Q)SPI Flash (most Adafruit M0, M4, nRF52840 boards)

Library Installation

You'll need a few libraries, install them through the library manager!

Search for and install Adafruit Sensor Calibration

We strongly recommend using Arduino IDE 1.8.10+ because it will automatically install any dependancy libraries. If you have to install manually, grab SdFat - Adafruit Fork, ArduinoJson, Adafruit SPIFlash, Adafruit Unified Sensor as well (see all dependencies here)

Compilation & Upload Check

Load sensor_calibration_read example - yes even though there is no calibration yet, this will let us verify the basics!

EEPROM Storage

First we'll try loading it into a chip with EEPROM (an ATmega328-based Metro mini!)

Here's what you should look for:

  • At the top you'll see that Has EEPROM is 1 - indicating we're using the internal EEPROM
  • It's OK to see No calibration loaded/found (its a fresh chip!)
  • The hex block after the **WARNING** is the raw calibration data stored. It's normal to see all 0x00 or 0xFF's if this is the first time running the program.
  • Finally you'll see Calibrations found:
    • Magnetic Hard Offset should default to 0, 0, 0 (no offset)
    • Magnetic Soft Offset should default to 1, 0, 0, 0, 1, 0, 0, 0, 1 - note that isn't all zeros! It's a 3x3 identity matrix.
    • Gyro Zero Rate Offset should default to 0, 0, 0 (no offset)
    • Accel Zero Rate Offset should default to 0, 0, 0 (no offset)

If you got this far, you're good! Go to the next page where we try to write calibrations

Flash Storage

Here's what you can expect if you're using a chip with built in SPI/QSPI storage!

Here's what you should look for:

  • At the top you'll see that Has FLASH is 1 - indicating we're using the external SPI Flash storage and that it successfully Mounted Filesystem!
  • It's OK to see Failed to read file / No calibration loaded/found (we haven't made one yet!)
  • Finally you'll see Calibrations found:
    • Magnetic Hard Offset should default to 0, 0, 0 (no offset)
    • Magnetic Soft Offset should default to 1, 0, 0, 0, 1, 0, 0, 0, 1 - note that isn't all zeros! It's a 3x3 identity matrix.
    • Gyro Zero Rate Offset should default to 0, 0, 0 (no offset)
    • Accel Zero Rate Offset should default to 0, 0, 0 (no offset)

If you got this far, you're good! Go to the next page where we try to write calibrations

Flash Unformatted Error

There's a chance, if you have a totally fresh board, that the flash is unformatted. In this case, when you upload the calibration reader, you'll get that the JEDEC Chip ID was read (it may vary), and that the flash size was detected - but failed to mount newly formatted filesystem!

If that happens, you have two ways to format the filesystem.

  1. Easiest way (we think) is to install CircuitPython - that's because you don't have to compile anything - simply enter the bootloader by click/double-clicking, and dragging over a UF2 file which will format the disk for you.
  2. Or, you can load the SdFat formatter example in the Adafruit SPIFlash library:

Compile, upload and check the serial monitor for instructions

Now re-upload/re-try the sensor calibration reading demo

This guide was first published on Feb 17, 2020. It was last updated on Feb 17, 2020.

This page (Calibration Pre-Check) was last updated on Dec 04, 2021.

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