LPC1549 UART RS485 Auto Direction control

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by Carl-CircuitWorx on Fri Jun 19 11:25:19 MST 2015

Have set up DMA on UART1 to TX an array and configured RS485 control of the RTS line by setting the bits  UART_OETA, UART_OESEL, UART_OEPOL
It works but I can see the direction line blipping between each byte even with the OETA bit set which should delay a change of the direction line for the width of 1 character.

Have attached an screen cap of the trace from a logic analyser, top trace is with out OETA set, bottom is with.

I can't see any other settings to change, I could use the pin in gpio mode at the start of TX and switch to RTS once the DMA IRQ Fires I suppose.

Any ideas?