Using the com port on the iMX53

[leonardfairclot]

Has anyone created an application that opens the com port and listens to incoming messages and sends a response?

I'm writing in C and I believe that the "stdio.h" should have everything I need.  When I try to open the port I get error messages.  It doesn't seem to like the parameters:

int portnum

portnum = open("dev/ttys0", O_RDWR | O_NOCITY | O_NDELAY);

[leonardfairclot]

Weidong Sun

Thanks, this was very helpful.  Just a question for you. Is there a reason you use "ttymxc1"?  I'm using the quick start board iMX53 and it only has one serial port on it.  I was trying "ttymxc0", just curious if you knew what I should use for this board.

Thanks

Leonard

[weidong_sun]

Hello,Leonard,

     you please pay attention to ttymxc0 on mx53QSB, this is UART1 hardware, on this board, UART1 is used by console. when system startup , all messages ouput to console via this port. So you had better not use it to communicate with other device.

Regards,

Weidong

[leonardfairclot]

Good point Wiedong, I need a serial port do you have any other suggestions?  I could go USB to Serial but I really wanted to avoid that.  What port are you using and did you have to configure the serial port before you were able to run your program?  i was just reading about "minicom".

Thanks

Leonard

[weidong_sun]

Hello,Leonard,

      UART4 & UART5 can be iomuxed by CSI0 port. On i.mx53QSB , by default these pins are used for carmera and connected to J13.

      You may consider how to connect them outside and do UART test. In addtion, Don't forget to adjust BSP file: add these pins to mx53_loco.c.

      You can get iomux pins mapping by mcimx53rm.pdf. please refer to it !

CSI0_DAT12--->UART4_TXD

CSI0_DAT13--->UART4_RXD

CSI0_DAT14--->UART5_TXD

CSI0_DAT15--->UART5_RXD

<Note: UART4--->ttymxc3; UART5--->ttymxc4, the level of these 2 ports are 1.8V >

Regards,

Weidong

[leonardfairclot]

Thanks Weidong

I'll try that, not tonight.  When i run your app, I get "open uart error, please confirm if this device exist"I tried "ttymxc0" and "ttymxc1" with the same results.  The open routine is returning a "-1", is this an error that can be looked up? 

Thanks

Leonard 

[weidong_sun]

Hello,Leonard,

    you please check all uart devices in path /dev/:

# ls -l /dev/ttymxc*

to confirm if uart devices have been driven.

Regards,

Weidong

[leonardfairclot]

Nothing is found.  How do I add uart devices\drivers?

[leonardfairclot]

I have tty0-63 and ttys0-31.  No ttymxc*.

[leonardfairclot]

Sorry, I was looking on my development PC, I found them on the development board. I have "ttymxc0-4" on the iMX53.

[leonardfairclot]

The permission on ttymxc0 is "crw-------" where as all the others are "crw-rw----"  could this be the issue?  Chmod will not all me to change the permission.  What do you think?

[weidong_sun]

don't use ttymxc0. use others please ! For example , use UART4:

#chmod 777 /dev/ttymxc4

Then run your program.

Weidong

[leonardfairclot]

I'm logged in as lucid and don't have permission to chmod this file.  How can I get around that?  I don't believe there is a root on the iMX53, right?

[weidong_sun]

Are you using ubuntu system on mx53QSB ?

weidong

[weidong_sun · Accepted solution]

If you are using ubuntu, you can use root account like this :

#sudo bash

Then input lucid .

weidong

[leonardfairclot]

Thanks for your help tonight.

I should be working at it again Sunday night.

Leonard

[leonardfairclot]

Nice!  Thanks  I got past the first error now I'm getting a segmentation fault..  Let me look at that.

Thanks again

Leonard

[leonardfairclot]

Any idea as to why I'm getting a segmentation fault?  I out a few print statements to see where it may be crashing and not luck so far.  I'm calling a procedure to open the port, then when I return I check to see if there is anything in the buffer?

Thanks

[weidong_sun]

Ok, you can run your program on board, and check if UART has been opened successfully.

Regards,

Weidong

[Yuri]

In the same time there are no other UART connectors on the i.MX53QSB (except one for UART1).
Basically it is possible to use console.

[leonardfairclot]

That's good news, is there something I need to run before trying to open a port within a program.  What does "minicom" do?