Hello @Andrew_D,
Thank you for your advice, however I did what you told me. I have installed already AC vers 4.05 and my quad copter fly well. I also did set the BRD_BOOT_DELAY to 2000 ms (I think the unit is ms instead of second). But still not go. I assume you don’t use Windows10 do you? I strongly believe this is because of Win10 driver problem. The reason is : In the device manager of Win10, that Flow sensor has error mark which means driver problem or other problem (that still don’t know yet). I use I2C connector for this PX4Flow sensor. Hope some one can solve my problem. Thank you.
In this case I cannot help you. I use Windows 7 and XP. This is also the reason I update my OS and other software only when absolutely necessary. Despite all the promises there are always problems with new versions. Please keep me posted as I am being forced to soon update my Windows to 10.