[DEV] Sending data from fast_loop run at 400 Hz? What am I missing?

Hello everyone,

I try to send data to via uart from Copter::fast_loop() (I am just testing it for simple byte like 0x0a or so) and I need those data to be sent at 400 Hz frequency, which fast_loop() should run at.

When I connect uart to logic analyzer, it shows that bytes are being sent with different frequencies (period between sending of two bytes varies too much). I am using Pixhawk. Is there any logic behind this? Could anyone explain why is this happening? Is there any blocking on uart or are those bytes being pushed to some buffer?

Thanks for any help!