UART2 Receive Buffer Overflow

Discussion of your EDM baseboard, your add-on boards or other peripherals for your wandboard.

UART2 Receive Buffer Overflow

Postby premier_10115 » Thu Sep 03, 2015 5:44 am

Hi,

I am using WandBoard Quad with Technexion Fairy Board as the baseboard. I am using linux kernel 4.0.5 and I configured UART2 in the device tree. I used minicom to check the UART (ttymxc1). The transmit seems to work perfectly, but the problem is with receiving. The receive buffer seems to overflow after 31 characters and the board goes to poweroff. I cant seem to figure out where the problem lies.

Could someone help me with the issue. Did someone had luck with UART2.

Best Regards,
Pranav
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Re: UART2 Receive Buffer Overflow

Postby fLo431 » Fri Sep 04, 2015 5:55 am

Hi Pranav,

I have the Wandboard Quad only.
However your problem sounds like some Buffer issue. Like you are reading the data from your buffer but not clearing the data, I had this at x86 in the past (but with DOS).

Your Kernel sounds very new too (I work with 3.10).
I recommend to check into the Buffer (or FIFO) and make sure it is cleared. I think this buffer is 32byte (at x86) and that sounds like you recive data,read them out, but don't clear (reset) the buffer.

Try google like 'UART FIFO overrun, UART FIFO Buffer clear or RX Buffer'

Flo
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Re: UART2 Receive Buffer Overflow

Postby premier_10115 » Sat Sep 05, 2015 3:52 am

Thank you. I will check it out. This is very strange because the UART1 (ttymxc0) seems to be working fine for the same code i created. I used the basic serial transmission using Minicom, and it doesnt work for UART2.
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Re: UART2 Receive Buffer Overflow

Postby Tapani » Mon Sep 07, 2015 8:03 am

Are you using DMA for any of your UARTs?

I vaguely remember reading about some problems with UART and SDMA. Note that the DMA block for iMX6 should be the same (or very similar) to iMX5.
So maybe some of the threads contain something helpful:
http://stackoverflow.com/questions/1513 ... ale-imx535
https://community.freescale.com/thread/304624

Being so much ahead of the curve (kernel 4.x) has its disadvantages too.
Tapani
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Re: UART2 Receive Buffer Overflow

Postby premier_10115 » Wed Sep 16, 2015 5:06 am

Tapani,

You were right. I think it is the problem with using latest kernels. I couldn't find out why it was happening and how to fix it. So, I used the Wandboard git kernel 3.10.17.1.0.0 and it is working fine. No Rx buffer overrun. :D

Thank you.
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