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The 3DR Iris+ with 3DR radio and 3DR RC receiver


The Iris+ drone was manufactured by 3DR and is based around the Pixhawk autopilot. Paparazzi supports the Pixhawk hardware, and this page serves as simple step-by-step guide to get a Pixhawk based drone flying on with the Paparazzi autopilot. In this example, only standard Pixhawk hardware is used, as it comes delivered with the stock Iris.

Getting the Iris flight ready

You'll need:

  1. The stock Iris drone, (equipped with the Pixhawk),
  2. Its stock 3DR radio's and 3DR RC.
  3. The Pixhawk should still contain the PX4 / APM bootloader.
  4. A computer with Paparazzi installed.
  5. A micro USB cable.
  6. Optional: the 3DR Tarrot Gimbal and a GoPro 3.

Steps you will need to perform:

  1. Plug in the USB cable to the Iris. Remove the props. Leave the battery disconnected.
  2. Flash both the AP and FBW. See here
  3. Power cycle the Pixhawk (e.g. replug USB).
  4. Make sure to set the target to AP again, and build.
  5. Plug in the 3DR radio to the computer. Select USB0 session in Paparazzi Center.
  6. Calibrate the IMU and the ESCs of the Iris+.

Calibrate the ESCs

The original PX4 firmware calibrates the ESCs automatically, paparazzi does not support this. Therefor it is needed to calibrate the ESCs manually. For this two options are available:

  • Calibrate by using a servo tester
  • Calibrate using mode RC direct

The first option requires the user to have a servo tester, open up the Iris+ and disconnect wires. Therefor, this wiki describes the second option.

In order to use the RC direct mode, a change is required in the airframe xml configuration. Check if the following lines are configured in the section AUTOPILOT:

File: conf/airframes/TUDELFT/tudelft_iris_indi.xml
<define name="MODE_STARTUP" value="AP_MODE_ATTITUDE_DIRECT" />
<define name="MODE_MANUAL" value="AP_MODE_ATTITUDE_DIRECT" />

Secondly, comment or temporarily remove the following line:

File: conf/airframes/TUDELFT/tudelft_iris_indi.xml
<define name="FBW_MODE_AUTO_ONLY" value="true"/>

Important: for safety it is strongly recommended to remove the propellers
Note: mode RC direct ignores the radio kill switch and software arm procedure, throttle is directly commanded through the stick.

Close up of the 3DR RC receiver. 1) The manual Kill switch. 2) The Gimbal control. 3) The mode switch.

Build and upload the FBW firmware.

The system is now ready to calibrate the ESCs. Perform the following steps:

  • Power off the Iris+
  • Turn on the RC, the set radio mode (switch 3 in figure 2) to std, and put the throttle to max.
  • Plug in the battery to the Iris+ (with props removed!). You should hear two beeps from the ESCs.
  • On the RC, put the throttle to zero. You should hear another beep from the ESCs.
  • Validate the range of the throttle stick by slowly throttling up to max. The motors should spin accordingly.