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TM4C129ENCPDT: UART & RS485 RTS pin driver for DE/RE

Part Number: TM4C129ENCPDT

Tool/software:

Hi all,

I'm currently having some difficulty getting the RTS pin of my UART to activate upon transmission (so it can drive the DE/RE inputs of an RS485 transceiver). The actual Tx/Rx of data works fine.

I'm using UART3 and am using pin PP4 for U3RTS. I've set the pin as an output and set the modem control via "UARTModemControlSet(UART3_BASE, UART_OUTPUT_RTS)".

When operating the pin as a regular flow control pin for RTS/CTS it works fine, but for whatever reason the functionality detailed in section 19.3.6 of the datasheet doesn't seem to be working



The UART_CTL register has the UART_CTL_RTS set and UART_CTL_RTSEN unset, are there any other register settings I should be checking?

I'd prefer to not have to drive the pin manually as a GPIO pin in the Tx interrupt if possible.

Any assistance would be appreciated!

Kind regards,
Gerard.