SLAA457B September   2013  – October 2018 MSP430F5500 , MSP430F5501 , MSP430F5502 , MSP430F5503 , MSP430F5504 , MSP430F5505 , MSP430F5506 , MSP430F5507 , MSP430F5508 , MSP430F5509 , MSP430F5510 , MSP430F5513 , MSP430F5514 , MSP430F5515 , MSP430F5517 , MSP430F5519 , MSP430F5521 , MSP430F5522 , MSP430F5524 , MSP430F5525 , MSP430F5526 , MSP430F5527 , MSP430F5528 , MSP430F5529 , MSP430F5630 , MSP430F5631 , MSP430F5632 , MSP430F5633 , MSP430F5634 , MSP430F5635 , MSP430F5636 , MSP430F5637 , MSP430F5638 , MSP430F5658 , MSP430F5659 , MSP430F6630 , MSP430F6631 , MSP430F6632 , MSP430F6633 , MSP430F6634 , MSP430F6635 , MSP430F6636 , MSP430F6637 , MSP430F6638 , MSP430F6658 , MSP430F6659 , MSP430FG6425 , MSP430FG6426 , MSP430FG6625 , MSP430FG6626

 

  1.   Starting a USB Design Using MSP430™ MCUs
    1.     Trademarks
    2. 1 USB and the Art of Making Something Complex Look Simple
      1. 1.1 What Has Made USB So Successful?
      2. 1.2 But It Looks So Simple!
      3. 1.3 TI's Approach for MSP430 USB
    3. 2 MSP430 USB Silicon
      1. 2.1 How MSP430 Devices are Documented
      2. 2.2 USB-Equipped MSP430 Derivatives
      3. 2.3 MSP430 USB Module
      4. 2.4 USB Certification of the Silicon
    4. 3 Software
      1. 3.1 USB Developers Package: Overview
      2. 3.2 USB API Stacks: Features
      3. 3.3 MSP430 USB Descriptor Tool
      4. 3.4 Host Software, and the Java HID Demo App
      5. 3.5 USB API Programmer's Guide and Examples Guide
      6. 3.6 MSP430 USB Field Firmware Upgrade Tools
    5. 4 MSP430 USB Hardware Design
      1. 4.1 TI Reference Design for USB Interface
      2. 4.2 Selecting a Power Configuration
      3. 4.3 Selecting a Clock Configuration
        1. 4.3.1 Choosing a Source
        2. 4.3.2 Choosing a Frequency
      4. 4.4 Other Reference Design Commentary
    6. 5 MSP430 USB Software Design
      1. 5.1 How to Choose a USB Device Class
      2. 5.2 How to Select a Vendor ID (VID) and Product ID (PID)
        1. 5.2.1 What are the VID and PID?
        2. 5.2.2 How are They Chosen (or Obtained)?
        3. 5.2.3 Using VIDs and PIDs During Development
    7. 6 Getting Started: Evaluating MSP430 USB
      1. 6.1 Software Development Environments
      2. 6.2 F5529 LaunchPad Development Kit
      3. 6.3 MSP430F5529 USB Experimenter's Board
      4. 6.4 FET Target Boards
    8. 7 More Information
  2.   A USB Glossary
  3.   Revision History

4.4 Other Reference Design Commentary

The circuitry within the dashed rectangle in Figure 8 is required only if the bootloader (BSL) is to be invoked using a pushbutton switch, for performing firmware updates through USB. PUR is normally an output, but in the moments following a BOR reset, it is an input that determines whether or not the BSL will be invoked. This pushbutton is only one way to invoke the BSL; see Section 3.6 for more information.

The weak pulldown resistor on PUR ensures that the PUR pin stays low if the pushbutton is not pressed. (It is weak enough to not disrupt D+ during USB operation.) This pulldown should never be eliminated, as doing so might result in unintended invocation of the BSL.

The pullup resistor is specified as 1.4k. Those with USB experience are aware that the pullup value specified in the USB specification (parameter RPU) is 1.5k. The reason for this difference is that the MSP430 device's PUR pin itself contributes approximately 100 Ω (shown as parameter RPUR in the device data sheet). The sum of this amount and the external 1.4k resistor produces the complete value RPU. To be absolutely compliant, a 1% resistor is needed. This is because the sum of the errors on RPUR and a 5% resistor slightly exceed the 5% allowed by the USB specification on RPU. Practically speaking, however, there is no problem using 1.4k ± 5%.

At 12 MHz, full-speed USB usually is not highly sensitive to transmission line characteristics, but it is recommended to keep D+ and D- reasonably short.

A USB port can represent an ESD vulnerability, because it extends a conductive path to the outside of the enclosure, which the user frequently touches. Under these conditions, the protection integrated into most ICs is not enough to withstand the levels of discharge it might experience. Therefore, a dedicated ESD suppressor is recommended, such as the TPD2E001 shown. It is important to follow all the design recommendations in the TPD2E001's data sheet.

The diode on VBUS is placed there to ensure compliance with the USB 2.0 specification's requirement that the device never source current toward the host over VBUS. This diode may not be needed in systems in which VBUS is the only source of power for the system.