AQ6 – Digital IMU upgrade
The Digital Inertial Measurement Unit (DIMU) expansion board for AQ6 replaces the AutoQuad6 onboard analog sensors and adds CAN, UART2 and Eeprom memory to AQ6.
- 9 axis digital IMU
- Highprecision digital pressure sensor
- Onboard CAN bus transceiver for communication with ESC32’s and a
- JST-SH 4 pin connector with UART2 serial connection (TX, RX, 5V, GND)
- Eeprom memory chip – use to store IMU calibration parameters, and never loose them again in a FW update
Advantages to using a DIMU:
Easier calibration: DIMU introduces new onboard calibration methods that allows you to calibrate a DIMU to a flyable state in less than 5 minutes. The process is described on the Onboard IMU Calibration page.
Better altitude hold: The new digital pressure sensor is much more precise than the old one, giving much better altitude hold without GPS.
Not succeptible to magnetic interference in flight: Due to increased gyro stability, Autoquad with DIMU now only uses the magnetometer to estimate initial compass heading on the ground before takeoff. Once you take off, the magnetometer is no longer contributing to the heading estimation. The craft will then maintain steady heading in flight just by using the gyros and accels and correcting with GPS (when available). This means that magnetic interference from power distribution can not affect heading estimation in flight.
Mounting the DIMU on the Autoquad board
Mounting the DIMU to the Autoquad board is not very hard if you have basic skills and tools for working with Surface mount soldering. But if you dont feel confident in mounting and soldering small headers, you can send your board into Viacopter and have it upgraded to DIMU for a fee. Send a mail to info(at)viacopter.eu to arrange DIMU upgrade.
Stuff you will need:
- Soldering iron with medium or small tip
- Desoldering braid and alcohol to clean with
- Soldering wire
- Paste flux or flux pen
- Clean up the J1 and J2 pads with desoldering braid and alcohol.
- Put the female headers onto your DIMU
- Line up the female headers with the SMT pads on the AQ6.
- You can use a small clamp to hold it in place. But clamp down directly on to the expansion headers. And remove the clamp right after soldering the two corner pins to hold it in place
- Solder a single corner pin in place
- Turn the board 180 degrees
- Check that the DIMU lines up with the board and then solder the opposite corner pin
- Recheck alignment between board and DIMU – correct if necessary
- When board and DIMU lines up, remove the clamp and solder the remaining outside pins and then remove the DIMU carefully from the female headers. Take care and go slow when pulling the DIMU from the female headers – the inside pins are still not soldered.
- Solder the inside pins of the female headers now attached to your AQ board.
- Clean up and inspect for shorts or solder bridges.
- Mount the IMU back in – put a small piece of open cell foam between the AQ6 board and the pressure sensor on the bottom of the board to protect it from gusts.
The baro is on the lower side of the DIMU board marked “U1”:
Firmware for DIMU (experimental)
For Autoquad 6 to use the new DIMU, you can download pre-compiled firmware from our FTP server:
You can also download a parameter file for instant use:
After connecting to the QGCS you will probably notice that the HUD is spinning around its axes or is totally off. That is because the DIMU does not have yet its calibration parameters stored or a TARE function is executed. For simple leveling, place the board level and perform the following stick sequence in DISARMED mode:
NOTE: If you can´t use the TARE function like shown in the video you might need to reverse the Pitch.
Then it´s Pitch down, Throttle down, Rudder (YAW) left and Roll left (so basically both sticks in lower left corner). The DEBUG led onboard should lit and after a second when you let go of the stick to return to default position the HUD should display a perfectly leveled board.
Once you have found a level place to use the TARE function, you should store the parameters in the flash memory of the AQ. Otherwise you´ll need to TARE again each time you repower the board.
Saving the values in the EEPROM is currently not working and will be introduced in a later firmware version.
This is how an uncalibrated AQ6 +DIMU performs in gusty winds:
More videos in our YouTube AQ6 +DIMU Playlist