Hi
I’m currently running v3.2.1 in a mini-APM on a 250 size quad.
I’d like to you use the new ‘emergency motor stop’ ‘motor interlock’ features but these only became available in v3.3.
I’m not sure my mini-APM will run v3.3 ???
Are there any known issues with v.3 ?
If I save my .cfg file is it easy then to return to v3.2.1 ? is everything saved in the file?
All replies appreciated 
Thank you
Steve 
Hi
Unfortunately none of the APM boards can run firmware greater than Arducopter v3.2.1 as the Atmel MCU does not have enough flash memory to store the code. You will need to use a autopilot with one of the STM32 MCU, or modify the code to remove some parts so you can add the emergency motor stop.
However since you are so helpful the he forums I will be happy to offer you a 50% discount should you want to upgrade to one of our pixhawk based systems like PX4 racer, or Unmanned Hawk (pixhawk clone since 3DR no longer make it)
Hi Alex
I bought from you a MiniHawk PX4 Mini AIO V1.4 back in November
I cannot see on the spec sheet what the MCU is but from your answer a few minutes ago I’m assuming this mini version will do the job, can you confirm?
If it is OK then I suppose I should get my finger out and fit it 
Cheers
Steve
Hi Alex @unmannedtech1
I’ve looked at these again and can see my PX4-mini
Is not the same as the PX4Racer
I’ll send you a PM email
Thanks
Steve
The PX4 mini is equivalent to the px4racer, just that due to some supply chain issues we now replaced it with t px4racer. But both should support the latest versions of arducopter.