LPC54628 RS485

[lua40927]

Hi all,

I want to use the UART function of LPC54628 via RS485.

Regarding the setting of RTS, I set OESEL.OEPOL.OETA according to the manual.

The IOCON setting of the RTS pin pin is as shown below

but I still failed.

I would like to ask how to use RS485

Thanks

[xiangjun_rong]

Hi,

I think your configuration is correct for both pin assignment and RTS configuration.

After you write the FIFO write data register of FC1 module, can you check the PIO0_14 signal (RTS pin)if the RTS signal toggles?

I suggest you continue to write the FIFO write data register of FC1 module with polling or interrupt mode in a loop, then check if the RTS signal toggles.

BR

XiangJun Rong

[lua40927]

Hi,

I use a WHILE loop to keep sending data.

The waveform of RTS is as follows

It looks like it's working.

But the information received is incorrect

Looks like there is some problem

Thanks for taking the time to answer

[xiangjun_rong]

Hi,

From the screenshot signal, it appears that the RTS signal is not well, it should have been square waveform with clear rising/falling edge, do you know the reason for example the limited bandwidth of the scope or the signal itself?

Can you show the waveform of both TXD and RTS so that we can see the relationship?

BR

XiangJun Rong

[lua40927]

Hello,

The following are the parameters I set , 

USART_CFG_OESEL(true) | USART_CFG_OETA(true) |  USART_CFG_OEPOL(true)

In the case of Baud Rate 9.6kbps:

Blue : Tx   Pink:RTS

The difference between the following two signal graphs is only the width of the time axis

0.25ms:

0.1ms:

I send data 0x11 continuously,and I received the correct data 0x11

In the case of Baud Rate 57.6kbps:

Blue : Tx   Pink:RTS

The difference between the following two signal graphs is only the width of the time axis

0.1ms:

0.025ms:

I send data 0x11 continuously,but I received the error data 0xC4

I think the rise of RTS is too slow, resulting in errors when the baud rate is faster

Do you have any solution? 

Thanks