Yellow Double Flash LED after power up

When I power up my IRIS I get the a Yellow Double Flash LED ( /Y-Y-space/repeat, no tone)

I understand this means a system error.

I have update to the latest version of the Firmware using APM Planner 2 (Mac OS X). This doesn’t change the behavior of the IRIS.

With APM Planner 2 (Mac OS X) attached via wireless to the IRIS I was expecting the HUD to show what error is occurring, but nothing is displayed. There is also no error listed in the Messages display.

What should I be doing to diagnose the cause of the Double Yellow Flash?

If you can, you might try powering up the Pixhawk while holding down the arming switch to be sure that the FMU has updated the IO section firmware since your last update.

Will do.

The firmware is reported as updated. When the IRIS powers up it still goes through the dames steps
Main LED
For 2 sec - start up tune
For 2 sec Flashing /Y-Y-dark/ repeats
Then for 2 secs flashing /Red-Blue/ repeating
Then repeating flashing /Y-Y-dark/

Arming LED is flashing /R-R-R-R-dark/ repeating
It can be armed, LED /R/ on, and plays upward tune

In APM Planner 2.0, via MAVlink, the reported messages are

[MAV 001:1] Initialising APM…
[MAV 001:1] barometer calibration complete
[MAV 001:1] ArduCopter V3.1.5 (ee63c88b)
[MAV 001:1] PX4: 9eb74dea NuttX: 65cd7f85
[MAV 001:1] PX4v2 2F002100 0C473233 35393334

and that is all.

Can you please advise what further diagnostic I should try?

(and just to be clear I the IRIS will not start, when commanded by throttle-bottom-right).
The Double Yellow Flash just continues. No further messages in APM Planner 2,

A fix involved changing the ARMING_CHECK in the APM:copter parameters.

At start up with the yellow LED flashing, the Planner HUD window does not report any GPS Fix issue. However, in the Quick Display the GPS HDOP is showing 99.99m.

I used APM Planner v2.0.9 > Config/Tuning > Standard Params to change the Arming Check (ARMING_CHECK) to “Skip GPS” which is a mask value of -9

After powering the IRIS down and up again, it was now possible to get a blue flashing light, then arm the IRIS, and to get the rotors to spin.

I changed the Arming Check (ARMING_CHECK) back to Enabled which is a mask value of 1.

Now the logic in the start up appears to work: The IRIS will now acquire a GPS fix and transition from Yellow Double flash to a Green Flash.

If the IRIS is unable to get an adequate fix the APM Planner v2.0.9 now reports an "M1 Prearm Check: Bad GPS Pos”, and the /Yellow-Blue/ repeating LED shows.


The logic in the APM:Copter software and the APM Planner v2 need to ensure that if the Preflight checks fail, an explanation is shown in the HUD, in this case a GPS Fix warning.

It would help if the IRIS LED gave a different indicator that the GPS fix was this issue. Surely a Blue/Yellow flashing LED would be consistent?

Selecting the STABILIZE mode should allow the pre-arm to proceed even when the GPS is not available.


The symptoms that I was experiencing seem to be referenced in multiple other threads.

The IRIS was unable to get an HDOP <= 2.0 even after sitting in an open field for more than two hours. This what was causing the double yellow flash at startup. Recycling power would make no difference.

The APM Planner 2.0.9 software was not reporting the reason for the prearm failure in the HUD. The HDOP was elevated, but I didn’t know enough at the time to understand this was stopping the prearm checking. I changed to 2.0.10 and it looks like this issue may have been fixed, in that a Message saying PreArm:High GPD HDOP now appears in the messages window.

I’m using APMcopter 3.1.5 firmware. The prearm logic does not currently appear to match the manual. I there is a high GPS HDOP you are still supposed to be able to take off in Stablize or Altitude Loiter modes? This is not the currently the case. At present, if you fail the HDOP test you are grounded unless you use APM Planner 2 to change the prearm check logic (skip GPS) , or you increase the GPS_HDOP_GOOD parameter.

Given that I have now had many prolonged episodes spread over many weeks of the HDOP staying in the range 2.3-3.5 when used in open ground I am wondering if there is something wrong with my GPS receiver? Is there a diagnostic I can run, or specific test that can diagnose issues with GPS functionality ? Should I switch the receiver for another one?