1 1. For UART drivers in blocking mode, the readCancel() and writeCancel()
2 post the UART object's readSem and writeSem. In FreeRTOS, there doesn't
3 seem to be a way to know if we're in ISR context or not. In ISR context,
4 SemOSAL_postFromISR() must be used instead of SemOSAL_post().
5 So we'll assume writeCancel() and readCancel() are not being called from
6 ISR context and use SemOSAL_post().