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The Communication Speed of Virtual Com Port Between MSP430 Launch Pad and PC?

Chris YAN
Prodigy 210 points
Other Parts Discussed in Thread: MSP430F5529, TDC7200EVM

The Communication Baud Rate of Virtual Com Port Between  MSP430 Launch Pad and PC?

  • 0
    TI__Mastermind 21685 points

    Default baud rate is 38400. 

    Thanks,

    Vishy

  • 0 in reply to Vishy Viswanathan
    Prodigy 210 points

    Hi Vhishy,

    Thank you for your help. Will the communication rate adjustable and how can we set this?

    Bests.

    Chris

  • 0 in reply to Vishy Viswanathan
    Prodigy 210 points
    What will be the max communication rate through the virtual com port? We just know that the data sending is defined by function “cdcSendDataInBackground” in the related head file, but we did not find any adjustable parameter that can be used to set the communication rate.

    Bests,

    Chris
  • 0 in reply to Chris YAN
    TI__Mastermind 21685 points

    Chris,
    I have to clarify here. With the MSP430F5529 Launch pad, there are multiple communication ports to the host PC.
    a) There's a USB CDC device class based communication which uses a virtual COM port on the USB host. This device appears to users as TDC7200EVM communication port.
    b) Also, there's a simpleUsbBackchannel that can send/receive data over the UART. This is also over a virtual COM port USB connection and appears to users as MSP Application UART.

    The 38400 baud rate is for communicating on the MSP Application UART. You can read more about the back channel UART in the launchpad user guide
    www.ti.com/.../slau533c.pdf

    For USB CDC class device, there's no baud rate setting required. You can refer to the programmer's guide that's part of this package below
    www.ti.com/.../msp430usbdevpack
    for details of maximum throughput when using the USB CDC stack. CDC uses bulk transfers which has the potential to reach the highest data rates by using any spare bandwidth. USB full speed maximum is 12Mbps. But the actual transmission speed achieved would be much lower like 2 to 4Mbps.

    Thanks,
    Vishy

  • 0 in reply to Vishy Viswanathan
    Prodigy 210 points
    Hi Vishy,

    Thank you very much for your help. Is it means that when using function "cdcSendDataInBackground" from related head file and its corresponding CDC_virtualCOMport driver, we are using CDC based communication? And its speed can not be controlled and will be likely around 2 to 4 Mbps?

    Bests,

    Wenrong
  • 0 in reply to Chris YAN
    TI__Mastermind 21685 points
    Yes, all the function calls that begins with "cdc" implies you are using CDC based communication. Yes, depending on USB traffic and bus latencies your effective throughput is likely to vary.
  • 0 in reply to Vishy Viswanathan
    Prodigy 210 points

    Hi Vishy,

    Thank you for your help and at this stage we can get a baud rate up to 115200 baud. 

    However according to the User's Guide of MSP430F5529 LaunchPad Development Kit, page 13, the speed can be up to 1Mbaud. 

    But as we have tried different speed settlement, it turned out that the speed can not be over 115200 baud 

    and do you have any idea how we can get a higher speed over 115200 baud?

    Bests,

    Chis 

  • 0 in reply to Chris YAN
    TI__Mastermind 21685 points

    Chris,

    Could you please check about this in the MSP430 forum? 

    Thanks,

    Vishy