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TMS320F28386D: USB CDC setting

Frederick LIN
Intellectual 600 points

Part Number: TMS320F28386D
Other Parts Discussed in Thread: C2000WARE

Hi,

We want to implement the USB CDC device reference to the C2000Ware example C:\ti\c2000\C2000Ware_3_04_00_00\driverlib\f2838x\examples\c28x\usb\usb_ex1_serial_structs.

Some question:

1. What it the real transmit bit rate in the hardware? 60Hz by AuxPull?  but TRM said full-speed(12Mbps) or low-speed(1.5Mbps)? how to decide?

2. Does USB interrup triggered fix every 1ms? Is it adjustable?

3. Some USB library call Interrupt_disableMaster() to pause all the interrups(in usbddfu_rt.c and usbringbuf.c ). It may pause our higher priority interrupts(such as motion control). Can we not to call Interrupt_disableMaster()? below is our USB interrupt  function.

4. Continue above, why CM not necessary to pause interrupts like CPU( Interrupt_disableMaster() in usbddfu_rt.c and usbringbuf.c )?

Thank you.

  • 0
    TI__Mastermind 45606 points

    Hi Frederick,

    I'll request a USB SW expert on our team to comment on most of your questions.

    Frederick LIN said:
    1. What it the real transmit bit rate in the hardware? 60Hz by AuxPull?  but TRM said full-speed(12Mbps) or low-speed(1.5Mbps)? how to decide?

    In Device mode the F2838x USB operates in full-speed (12 Mbps). In Host mode it can interface with either full-speed (12 Mbps) or low-speed (1.5 Mbps) devices. It'll depend on the what the USB is interfacing with.

    Best,

    Kevin

  • 0 in reply to Kevin Allen18
    TI__Mastermind 36735 points

    Hi Frederick

    1.  The usb_dev_serial example uses bulk endpoints. Using usb_dev_serial example, the maximum is 128 bytes / ms. 

    We have been able to achieve throughput between 7 and 8 Mbps (875 KB/s - 1 MB/s) using bulk transfers. This is slightly under the full speed maximum of 12Mbps. You can refer the usb_ex9_dev_bulk_throughput for this.

    2.  USB stack is interrupt driven,  Interrupt are fired when data is received and when data is transmitted. 

    3. Interrupt_disableMaster is called in usbddfu_rt.c file since it enters into the DFU mode and control is transferred to the boot loader in preparation for a firmware upgrade from the host. In the usbringbuf.c, it disables and enables the interrupts. This is done to prevent the possibility of corruption of the read index. 

    4. I could not understand your question, can you provide some more details.

    Best Regards

    Siddharth

  • 0 in reply to Siddharth Deshpande
    Intellectual 600 points

    Hi,

    for the 4th question, it called Interrupt_disableMaster only in __TMS320C28XX__, for example below picture.

    why it's not needed in CM?

    Thank you

  • 0 in reply to Frederick LIN
    TI__Mastermind 36735 points

    Hi Frederick,

    Will take a look and get back to you 

    Best Regards

    Siddharth