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CDC driver performance

Joaquim Duran
Prodigy 160 points
Other Parts Discussed in Thread: DM3730

Dear all,

I'm developing an application that read data from several ADCs. The main board is the module LogicPD DM3730 torpedo wireless with its evaluation board, which has connected an external board with has installed the ADC's. The external boards connects with LogicPD board thow the USB interface and using the CDC ACM driver. The external board sends data at a rate of 8 Mbits/sec but the DM3730 CPU runs al 99%, only reading data from USB. The kernel version that runs DM3730 is kernel-3.0-omap3logic-BSP-2.1-0.

However, in the document from TI, 'OMAP35x Linux PSP Datasheet 02.01.01.08', in page 42, USB CDC-DMA performance, shows transfer rates of 54 Mbits/second. I'm comparing then because in both scenarios, the CDC driver is used.

I would like to know:

- Is usual this transfer rate? 

- Does this issue happens with TI DM37x EVMs?

- Which configuration do you apply to the kernel?

- Do you have any sample accessing to a similar device? I'm programming the access to the device using the serial interface, is this correct? 

 

Thanks and Best Regards, 

Joaquim Duran

 

 

 

  • 0
    TI__Guru**** 170521 points

    I don't have much experience on DM3730, but here are some of my comments.

    - CPU runs @99% seems to tell that USB does not DMA, which will affect throughput;
    - As far as I know, TI only provides 2.6.37 kernel for DM3730. kernel-3.0-omap3logic-BSP-2.1.0 seems not a TI package, you probably need to check with its provider if DMA is enabled, not refer to a TI datasheet.
    - DM3730 has two USB controllers - EHCI and OTG, have you tried to use both?

  • 0 in reply to Bin Liu
    Prodigy 160 points

    Bin Liu,

    2 - Right, TI provides 2.6.37 kernel for DM3730. I was thinking that the kernel-3.0-omap3logic-BSP-2.1.0 was a modification of TI kernel.

    3 - I've tested both both in both controllers, CPU load gets 100%.

    Thanks for your answer.