Pixhawk will not arm, bad compass health, no compass installed?

Thanks in advance for any help
New to Pixhawk, bought one from a buddy that was moving, I know it worked before he had it on a quad, all I bought was Pixhawk board.
First try using the Pixhawk , usb connected Ok, loaded Copter 3.5.4 Ok, flight modes are all stabilize for now, no buzzer, no GPS with compass, no safety switch (disabled safety check BRD_SAFETY_ENABLE=0), disabled all pre arm checks in standard parameters. Followed all mandatory hardware setup seemed Ok, unchecked all boxes in compass setup, when I try to arm, message in HUD is ARM COMPASS NOT HEALTHY, and main led on Pixhawk is double flashing blue like it needs GPS lock or something?
I know BAD COMPASS HEALTH has been asked before, but I don’t have a compass installed. Any ideas to fix or is there a parameter that totally disables compass?

Pixhawk, APM Copter, firmware Ardupilot Ver 3.5.4, Flysky TH-9X, Flysky PWM receiver, PWM to PPM encoder

It can not operate without a compass. Pixhawk includes one inside. You can use that one if you do not have an external one but…
You need to activate it, and it looks like you deactivated it by disabling all checkboxes in the compass calibration setup.

Don’t recommend flying a copter with just an internal compass. Most folks use a GPS with an intergrated compass and disable the internal compass on the pixhawk

To add to the choir remember that GPS is not just for auto missions and navigation. Many of the flight modes you might want to use require GPS.

Arducopter wants you to go through the basic calibrations, even if you turn off the arming tests later.

Thanks for trying to help guys Seems to be OK now, and if anyone runs into same problem.
When I was having all the arming (bad compass health) problems I was using Mission planner and Ardupilot Copter 3.5.4 and MP never saw the internal compass or gave me any option to set it up?
I switched to APM Planner 2 software loaded firmware Quad 4.6.7, did hardware setup, Planner gives option to setup onboard compass, calibrated, and all is working OK so far, no arming problems, no bad compass health?

Arducopter auto-detects the compass. So maybe there was a parameter corruption and it was not detecting properly.Now that you have loaded the PX4 stack you could re-try loading Arducopter and see if the problem went away when you over-wrote the memory.