The Nano's motion sensor (IMU) measures tilt and rotation through the flight. Calibrating it teaches the Nano what level and still look like for your particular board, which keeps the angles, tilt and rail angle accurate.
It takes a couple of minutes and you only need to do it once, though you can repeat it whenever you like. An uncalibrated Nano still flies and logs normally, but its angles are less accurate and the flight info page says it wasn't calibrated.
Starting a calibration
- Connect the Nano by USB and open
device_calibration.txton its drive. - Change the 0 on the first line to 1, save the file and eject the drive.
- Unplug the USB cable and switch the Nano on. Instead of getting ready for a flight, it starts calibrating straight away.
Running it on battery keeps the cable out of the way while you turn the board through each position. The Nano sets the first line back to 0 itself when it has finished. You can also start a calibration from the Nano USB Settings tool.
Step 1: Gyroscope
Lay the Nano flat on something solid and free from vibration, and don't touch it.
| LED | What to do |
|---|---|
| Solid red, 3 seconds | Step away |
| Flashing red, about 11 seconds | Keep it completely still while it measures |
| Amber | It moved. Let it finish, then run the calibration again |
| Three green flashes | Done, moving on to the accelerometer |
Step 2: Accelerometer
Next you place the Nano in six positions, one for each face, so it can measure gravity in every direction. It always asks for them in the same order, and shows each position's colour for 2 seconds before it starts.
| Colour | Position |
|---|---|
| Blue | Lying flat, component side up |
| Purple | Lying flat, component side down |
| Cyan | On its side, component side towards you, micro-USB to the right |
| Yellow | On its side, component side towards you, micro-USB to the left |
| White | Standing upright, component side towards you, micro-USB at the bottom |
| Green | Standing upright, component side towards you, micro-USB at the top |
While you line each position up, the LED tells you how it's going:
| LED | Meaning |
|---|---|
| Red | Wrong way up |
| Pink | Nearly there, but not square |
| Steady cyan | Lined up and measuring. Hold it still |
| Three green flashes | Position captured, move to the next one |
The rhythm is the same each time: line it up until the light turns cyan, hold still until the green flashes, then move on. There's no rush in between.
When it has finished
After the sixth position the Nano flashes blue five times and restarts. If it's plugged in, its drive disappears and comes back. The calibration is stored in the Nano's own memory and is kept when you switch it off.
To check it worked, open device_information.html and look for Calibrated on the calibration line, or reopen device_calibration.txt, which now lists the measured values with the first line back at 0.
The Nano also records how square and how still each position was held, and saves that calibration quality with every flight, so you can see it on each flight info page.