LPC MicrocontrollersのトピックRe: how to invert RTS signal of USART?

how to invert RTS signal of USART?

richardchenigt — Wed, 16 Mar 2022 15:58:43 GMT

Hi all, is there a way to invert the RTS signal of USART? I have a flexcomm configured as USART, and its RTS_SCL_SSEL signal is configured as RTS, instead of being a GPIO. In my application, I would like to see its output inverted, is there a way for the firmware to do so?

Thanks

Richard

Re: how to invert RTS signal of USART?

xiangjun_rong — Thu, 17 Mar 2022 02:53:11 GMT

Hi, Richard,

Can you tell us the part number you are using?

Assume that you use LPC5569, so pls refer to the UM11126.pdf

Pls refer to section 34.7.5.1 Hardware flow control

As the above figure, the RTS signal is an output signal driven by receiver. The RTS is configured to appear on a device pin so that it can be sent to an external device, it indicates to an external device the ability of the receiver to receive more data.

Unfortunately, we have not the code to demo the RTS function.

Hope it can help you

XiangJun Rong

Re: how to invert RTS signal of USART?

frank_m — Thu, 17 Mar 2022 10:08:43 GMT

> In my application, I would like to see its output inverted, ...

With using a standrd line driver like the MAX232 ?

Most RS232 drivers have inverting outputs.

Re: how to invert RTS signal of USART?

richardchennv — Thu, 17 Mar 2022 15:40:57 GMT

Thanks but I would looking for a way to configure it from firmware.

Thanks.

Richard

Re: how to invert RTS signal of USART?

richardchennv — Thu, 17 Mar 2022 15:45:12 GMT

Thanks Xiangjun, the part I am using is LPC54S018JxM, what I am looking for is to invert its polarity via firmware but I cannot find any level of control like this so far.

Thanks

Richard

Re: how to invert RTS signal of USART?

xiangjun_rong — Fri, 18 Mar 2022 01:22:02 GMT

Hi, Richard,

As I said that we have not the example code to invert the RTS, even the UM does not list the condition to invert the RTS signal.

The usart has receiver FIFO which has 16 entries, I suppose that you can enable the receiver FIFO, and you can receive the data, but you do not read the data from the receiver FIFO and check if the RTS can be inverted driven by the receiver when the FIFO is full.

XiangJun Rong