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Altera_Forum's avatar
Altera_Forum
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13 years ago

JTAG UART slowness

Hi All,

I am trying to write a file from the PC into SDRAM through the JTAG UART, and have found that it is quite slow. I only see about 1KB/s, and need to transfer files that are about 10-20MB.

At first I was using system console to write directly into SDRAM using the "master_write_32" commands. I thought maybe system-console is slow because it needs to control the nios processor in some way.

I then tried using the nios2-terminal with the command "cat file | nios2-terminal", and simple software to continually read the UART, but didn't find any improvement.

Next I tried using code included with the high speed image to transfer data (specifically to send data from the PC), but unfortunately didn't fix the problem.

I see that when I download the elf file speeds of 60KB/s are reported. Assuming that's true, then I don't think its my byte-blaster or cable etc.

Has anyone experienced something similar to this? Any help/suggestions would be greatly appreciated. Thanks!

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    --- Quote Start ---

    I am trying to write a file from the PC into SDRAM through the JTAG UART, and have found that it is quite slow. I only see about 1KB/s, and need to transfer files that are about 10-20MB.

    At first I was using system console to write directly into SDRAM using the "master_write_32" commands. I thought maybe system-console is slow because it needs to control the nios processor in some way.

    --- Quote End ---

    The fastest method is master_write_memory using the JTAG-to-Avalon-MM bridge.

    http://www.ovro.caltech.edu/~dwh/correlator/pdf/altera_jtag_to_avalon_analysis.pdf

    Cheers,

    Dave
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    --- Quote Start ---

    I see that when I download the elf file speeds of 60KB/s are reported. Assuming that's true, then I don't think its my byte-blaster or cable etc.

    --- Quote End ---

    All benchmarks have been most likely made with an USB Blaster. Byte Blaster is considerably slower due to the bit-banging method of generating JTAG signals.
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    And why not to use simple UART? There's SOPC/QSys UART component, but I'd offer to write Your own and use USB-to-UART converter, which is capable of a few Mbit/s.

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Thanks for the information it was very helpful. I mis-spoke in my earlier message. I'm actually using the USB Blaster. An old habit of calling it the byte blaster. I took dwh's suggestion and used the JTAG to Avalon MM Bridge instead of the NIOS, and used the write_master_memory command which speeded things up significantly. I now see ~100KB/sec which is good enough for my purposes. Thanks again.

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    --- Quote Start ---

    I took dwh's suggestion and used the JTAG to Avalon MM Bridge instead of the NIOS, and used the write_master_memory command which speeded things up significantly. I now see ~100KB/sec which is good enough for my purposes.

    --- Quote End ---

    Great!

    Cheers,

    Dave
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Hmmm.... If you expose the nios soft reset pins to an avalon slave you should be able to use the JTAG -> Avalon master interface to download software.

    This would significantly reduce the resource usage - especially if you don't need the I-cache for anything else.

    Technically the JTAG uart could still be present - but I suspect that is only included as part of the debugger.