Hi Dan,
Sorry for the late delay. I didn’t see your question at first.
It was a no brainer for me to use MQX 4.2.0 when it came available for the K64 and KDS 3.0.0. All my previous work was with MQX 3.4 to 4.1 with both Coldfire and Kinetis K60 devices and the CodeWarrior toolset. Most of my existing code ported over with little change whereas there are drastic driver changes in the SDK version of MQX. I was willing to make the changes for better future portability but I kept stalling on the lack of documentation and supporting examples on how I use the peripherals in real world applications. The full version of MQX had everything covered.
So to answer your question, the UART drivers in MQX 4.2 are very straight forward and there are many examples/documentation included and on this forum to use them as polled, interrupt, blocking, non-blocking, DMA and etc.
Mark