SLAU533D September   2013  – April 2017

 

  1.   MSP430F5529 LaunchPad™ Development Kit (MSP‑EXP430F5529LP)
    1.     Trademarks
    2. 1 Getting Started
      1. 1.1 Key Features
      2. 1.2 Kit Contents
      3. 1.3 Out-of-Box Experience
        1. 1.3.1 Step 1: Install a Software Development Platform
        2. 1.3.2 Step 2: Connect the Hardware
        3. 1.3.3 Step 3: Verify the storage volume has been loaded
        4. 1.3.4 Step 4: Open a text editor, and press the buttons
        5. 1.3.5 Step 5: Customize the strings
    3. 2 Hardware
      1. 2.1 Block Diagram
      2. 2.2 Hardware Features
        1. 2.2.1 MSP430F5529
        2. 2.2.2 eZ-FET lite Onboard Emulator
        3. 2.2.3 Integrated Full-Speed USB Hub
        4. 2.2.4 Power
        5. 2.2.5 Clocking
        6. 2.2.6 Application (or "Backchannel") UART
        7. 2.2.7 Emulator and Target Isolation Jumper Block
        8. 2.2.8 Isolation Jumper Block: 3.3-V and 5-V Jumpers
        9. 2.2.9 Isolation Jumper Block: Emulator Connection and Application UART
      3. 2.3 Measure Current Draw of MSP430 MCU
      4. 2.4 Using an External Power Source
        1. 2.4.1 External 3.3-V Power Source
        2. 2.4.2 External 5-V Power Source Without USB Connection
        3. 2.4.3 External 5-V Power Source With USB Connection
      5. 2.5 Using the eZ-FET lite Emulator With a Different Target
      6. 2.6 USB BSL Button
      7. 2.7 BoosterPack Plug-in Module Pinout
      8. 2.8 Design Files
      9. 2.9 Hardware Change Log
    4. 3 Software Examples
      1. 3.1 MSP430 Software Libraries: driverlib and the USB API
      2. 3.2 Viewing the Code
        1. 3.2.1 CCS
        2. 3.2.2 IAR
      3. 3.3 Example Project Software Organization
      4. 3.4 USB Configuration Files
      5. 3.5 Out-of-Box Experience: emulStorageKeyboard
        1. 3.5.1  Flowchart
        2. 3.5.2  Pre-Initialization
        3. 3.5.3  Initialization
          1. 3.5.3.1 Configuring the Keyboard
          2. 3.5.3.2 Configuring the MSC Interface
        4. 3.5.4  Handling SCSI Commands
        5. 3.5.5  LPM0 Entry
        6. 3.5.6  LPM0 Exit
        7. 3.5.7  Emulated Storage Volume
        8. 3.5.8  Sending Data as a USB Keyboard
        9. 3.5.9  Properly Handling USB Unplug Events
        10. 3.5.10 Non-Maskable Interrupt (NMI) Vector
      6. 3.6 Example: simpleUsbBackchannel
        1. 3.6.1 What It Does
        2. 3.6.2 Installing the CDC Interface
        3. 3.6.3 Operating the Example
        4. 3.6.4 Backchannel UART Library: bcUart.c, bcUart.h
        5. 3.6.5 Code Description: Initialization
          1. 3.6.5.1 Stopping the Watchdog
          2. 3.6.5.2 Configuring VCORE
          3. 3.6.5.3 Configuring Clocks
          4. 3.6.5.4 Configuring Ports
          5. 3.6.5.5 Initializing the Backchannel UART
          6. 3.6.5.6 Configuring USB
        6. 3.6.6 Code Description: Main Loop
        7. 3.6.7 Modifying to Use an HID-Datapipe Interface
      7. 3.7 Starting Device Manager
    5. 4 Additional Resources
      1. 4.1 LaunchPad Development Kit Websites
      2. 4.2 Information on the MSP430F5529
      3. 4.3 Download CCS, IAR, mspgcc, or Energia
      4. 4.4 USB Developers Package
      5. 4.5 MSP430Ware and TI Resource Explorer
      6. 4.6 F5529 Code Examples
      7. 4.7 MSP430 Application Notes
      8. 4.8 TI E2E Community
      9. 4.9 Community at Large
    6. 5 FAQs
    7. 6 Schematics
  2.   Revision History

3.6.5.3 Configuring Clocks

MSP430 applications typically use a fast clock and a slow clock. The fast clock (called MCLK) sources the CPU and peripherals in some cases, while the slow one keeps timers and peripherals operating during low-power modes. This approach reduces power: slow clocks consume less power, so the more often the fast clock can be disabled, the less power the application may consume.

Typically this fast clock is the digitally controlled oscillator (DCO) integrated in the MCU. The DCO itself is an important low-power tool, because unlike a crystal, it has a very fast start-up time, and thus can be quickly shut down and re-enabled. The DCO can be activated by an interrupt and stabilize fast enough to respond to it. An MCU's low-power modes are only useful if they can be used often.

Many MSP430 devices, including the F5529, couple the DCO with an frequency-locked loop (FLL) module that keeps the DCO locked to a precise slower-frequency reference. This gives good control over the DCO frequency.

The F5529 has three slow clocks available:

  • REFO: This is a modestly precise low-power on-chip oscillator that does not require a crystal. It operates at 32 kHz.
  • LFXT1: This is a crystal oscillator. It is very precise and lower power than the REFO, but it requires a crystal. It, too, operates at 32 kHz.
  • VLO: This oscillator is not very precise but does not require a crystal and has the lowest power of the three. It usually operates somewhere between 12 kHz and 20 kHz.

To keep things simple, the simpleUsbBackchannel example does not use any low-power modes; the CPU stays active at all times. As a result, all of these clocks are constantly active, and all functions are sourced from the DCO FLL. The emulStorageKeyboard example (see Section 3.5) does make use of low-power modes.

USB operation on the F5529 requires a high-frequency reference clock for the USB PLL. As mentioned in Section 2.2.5, this is sourced on the XT2 oscillator, and the F5529 LaunchPad development kit has a resonator on XT2. XT2 is managed directly by the USB API.

Table 9 shows the simpleUsbBackchannel example's clock configuration.

Table 9. Clock Settings

System Clock Source Speed Description
MCLK DCO, FLL 8 MHz MCLK is the MSP430 CPU clock. It is disabled in all low-power modes. There is no predefined MCLK lower limit for USB communication, but 8 MHz and higher are commonly used.
SMCLK DCO, FLL 8 MHz SMCLK drives high-speed peripherals. It is kept alive during LPM0 but disabled in LPM3, LPM4, and LPM5. LPM0 is the lowest power mode permissible during an active USB connection.
ACLK REFO 32 kHz ACLK is a low-speed clock that drives timers and slower peripherals. It is a very low-power way to keep the MCU alive during low-power modes. It is kept alive during LPM3 but disabled in LPM4 and LPM5.
USBCLK XT2 4 MHz USB operation on the F5529 requires a ±2500-ppm clock source on XT2. This application uses a precise crystal resonator. The USB module receives this clock directly from XT2.

For a full explanation of the MSP430 clock system, see the Unified Clock System (UCS) chapter in the MSP430x5xx and MSP430x6xx Family User's Guide.