Dear:

In the PDF of IOT2040, it supports UARTs as 3 mode(232,485,422),

and  I can not find the selection from the hardware setting.

Besides, I find the libmraa support UART to read&write something, but I have not found any function to set the 3 modes(232,485,422).

So I want to know how to set the mode to working in the 485 mode, thanks a lot.

jianwen

Nobody have experience to use the RS485?

Up!  who could help me or give some information to prompt?

thanks so much!!!

Firstly thanks your answer to my question, and I have tested the sytem according your instruction.

It works well, but I also can not run my RS485 example to run normally.

1. based on my IOT2040 board, X30 as send terminal and X31as receive teriminal, I used RS232 as communication protocol:

     1) I used basic linux method as below:

         int fd0,fd1, sendBytes, receiveBytes; char sendBuffer[100], receiveBuffer[100];

          fd0 = open("/dev/ttyXR0",O_RDWR); fd1=open("/dev/ttyXR1",O_RDWR);

           strcpy(sendBuffer,"Hello monkeys!");

          sendBytes=write(fd0,sendBuffer,strlen(sendBuffer));

          receiveBytes = read(fd1,receiveBuffer,100);

        I run the code like this, but I can not get what I want to, the sendByte=94, and receiveBytes =109.

     I can not get the reason of that result, could you  tell me why?

  2) when I used the mraa library to do it as below: 

int dev0,dev1, sendBytes, receiveBytes; char sendBuffer[100], receiveBuffer[100];

dev0 = new mraa::Uart("/dev/ttyXR0"); dev1 = new mraa::Uart("/dev/ttyXR1");

strcpy(sendBuffer,"Hello monkeys!");

dev0->write(sendBuffer,strlen(sendBuffer));

receiveBytes = dev1->read(receiveBuffer,100);

I can get the receiveBytes=14, so the result is what I want to.

so why the mraa library could get the result but normally linux method can not?

2. based on my IOT2040 board, X30 as send terminal and X31as receive teriminal, I used RS485 as communication protocol:

In this situation I use the command that you help me know (swithserialmode) change the Uart mode as RS485.

however, when I used the mraa library to send data from XR30 I could see the data from oscilloscope, but the XR31 can not got any data from the bus, so I want to konow:

maybe there are some method to switch send or receive based on RS485?

because I use the IOT2000 system just some days, so please give me some supports, sincerely thanks for that!

thanks for you replay, I have 2 IOT2000 (2040):

hardware version:  2G110  and 2G111

same linux version: B01.01.00.00_01.08.00.01

 look forward your answer....

Best wishes

1. the Uart485.zip is my project which include the linux method and mraa method.

2. To my second question, I modify and test the two uart is same mode(RS485) and same buardrate.

thanks for your answer.

To bergmanu:

Your answer is very useful and help me to solve my problem.

I have tested it on my hardware, which is ok based on RS232 mode.

However, I can not receive the data based on RS485 mode, although I set the X30&X31 to RS485 mode and same buardrate. Could you help again? thank you

ok, thanks for your help...

I am also trying to ...

Very sincercely thanks to you help me test the communication.

firstly, I try to use your method to test RS485, but failed.

then I try again, after many times it comes to ok, then always ok....so stranger(I just change the mode of UART).

I do not know why but forturately it is ok, thanks again to you.

Dear:

I am sorry, I cannot find the command switchserialmode in the new Image. like below:

-sh: switchserialmode : command not found

and when I use command:

find / -name switchserialmode

the result is null

bergmanu

The answers above are related to a pilot version of our SD-Card Example Image.

For the release version use:

 

switchserialmode rs485

 

Hi bergmanu, just to be clear here, if you set a serial port to rs485 with this release mode version, will it switch between send/receive modes automatically? 

Hello,

To change the port mode, you can use "iot2000setup" command in PuTTY.

It will open this setup page, go to "Set Serial Mode".

Select your port, X30 or X31.

Select the mode, RS232 or RS485.

Exit and call a reboot in PuTTY.

Your port is configure.

If anyone know how to set the baudrate, I would appreciate.

Everytime I try "switchserialmode", it seems to have change since the first post..

I try to set it to RS232, baudrate 9600.

Best regards,

Hugo

Hello,

I went further with the "switchserialmode" command, but still don't figure how to set the baudrate..

Best regards,

Hugo

Hi friend!

Try this:

With a SSH connection type IOT2000seup, the select the option as following:

Set Serial Mode - > [The port that you choice, X30 or X31] 

And then select the mode that you want!

icarogregorio

Hi friend!

Try this:

With a SSH connection type IOT2000seup, the select the option as following:

Set Serial Mode - > [The port that you choice, X30 or X31] 

And then select the mode that you want!

 Hello icarogregorio,

This is exactly what I said in my post of 3/15/2017 9:35 PM.

I would like to know how to set the baudrate.

Best regards,

Hugo

Hi,

I just need a confirmation whether the X30 port can both send and receive the data.Or should we define the direction for both ports like X30 to send and X31 to receive?

Regards,

Mathew

New question published by wkang is split to a separate thread with the subject Communication between IOT2040 and Arduino via internal UART (/dev/ttyS0, X11, pin0, 1).

Best regards
Jen_Moderator