WinCE UART RTS Toggle not working with DMA

We had an issue using our software and your recommended registry settings with the BSP 1.4 Beta1:

By default the UART B is now configured to use DMA (EnableDMA=1), but if you also enable RTSToggleAlwaysOn=1 and RTSPol=1 (which we need for RS-485), the RTS signal is actually set to low before all data is sent:


  1. RXD
  2. TXD
  3. RTS

As a comparison a similar telegram on BSP 1.3 Final:


Setting EnableDMA=0 in the registry solved the problem - but that wasn’t obvious at all.

Thanks for reporting this, we will look into it.