SWRA657 June   2020 CC3100 , CC3200

 

  1.   SimpleLink Wi-Fi CC3100, CC3200 Serial Flash
    1.     Trademarks
    2. 1  Introduction
    3. 2  How File System Content Gets to the Serial Flash
    4. 3  File System Guidelines
    5. 4  User File Mathematics
    6. 5  System and Configuration Files
      1. 5.1 Description
      2. 5.2 Memory Consumption
        1. 5.2.1 CC3200 Use Case
        2. 5.2.2 Host Driver Mapping
        3. 5.2.3 Minimum Flash Size
    7. 6  Implementing File System Features From Host Processor
      1. 6.1 Overview
      2. 6.2 File Listing
        1. 6.2.1 Requirements
        2. 6.2.2 Procedure
      3. 6.3 Free/Occupied Space
        1. 6.3.1 Requirements
        2. 6.3.2 Procedure
      4. 6.4 File Appending
        1. 6.4.1 Requirements
        2. 6.4.2 Procedure
    8. 7  Factors to Consider in Designing With Serial Flash
      1. 7.1 Serial Flash Vendor and Part Number Selection
      2. 7.2 Supported Flash Types
      3. 7.3 Frequent Write Operations
        1. 7.3.1 Serial Flash Access by the Wi-Fi System"
        2. 7.3.2 Seral Flash Access by the WiFi System
          1. 7.3.2.1 System Files
          2. 7.3.2.2 User Files
      4. 7.4 Sudden Power Off (power removal during a write/erase phase)
        1. 7.4.1 Battery Powered Systems
        2. 7.4.2 Line Powered Systems
    9. 8  Design Recommendations for Ensuring the Integrity of the Power Supply to the Serial Flash
      1. 8.1 Overview
      2. 8.2 Key Points
      3. 8.3 Brown-Out Mitigation Techniques for New Self-Hosted CC3200 Designs
    10. 9  Recommended Best Practices
    11. 10 Implications of Data Integrity Compromise to CC3100/CC3200
      1. 10.1 Recovery
    12. 11 References

8.2 Key Points

  • This document applies primarily to systems that are:
    • Powered from batteries
    • Powered by a hybrid line power and battery power scheme
    • This includes designs where the CC3x00 connects directly to the battery and systems where a DC2DC converter is used between the battery and the CC3x00
    • If the application uses a DC2DC converter then designers should ensure the output of the DC2DC converter satisfies the supply requirements of both the CC3x00 and the attached serial flash device.
  • CC3x00 devices should be enabled only when supply voltage is greater than or equal to 2.3 V. This minimum is typically determined by the serial flash minimum supply voltage and not the CC3x00 minimum supply voltage which is defined in the data sheet as 2.1 V. The key point is that the supply must tolerate a CC3x00 transmit current or calibration current load, as specified in the data sheet, without drooping below 2.3 V so the unloaded supply voltage may have to be greater than 2.3 V to account for internal resistance effects of the supply.
  • The supply voltage applied to the CC3x00 should never exceed 3.8V, specified as the absolute maximum supply voltage in the data sheet. And corresponding absolute maximum voltage constraints from the chosen serial flash data sheet must also be followed.
  • Follow TI serial flash design guidelines for CC3x00
  • Minimize the number of application writes to flash, especially after reset. For example make sure that application configuration writes to flash happen only at initial reset and not every time the CC3x00 is reset.
  • For maximum system robustness consider using a serial flash like the Macronix MX25R6435.This device supports a wide supply voltage range which tends to improve system immunity to supply fluctuations.
  • Keep in mind that CC3x00 WLAN transmission can result in sudden increases in the loading on the power supply and this may result in a momentary decrease in supply voltage. For a description on how to handle supply brown out, see the Brown-Out and Black-Out section of the CC3100 SimpleLink™ Wi-Fi® Network Processor, Internet-of-Things Solution for MCU Applications Data Sheet and the CC3200 SimpleLink™ Wi-Fi® and Internet-of-Things Solution, a Single-Chip Wireless MCU Data Sheet. Specific design scenarios are described in Table 10.

Table 10. Design Scenarios

Scenario Recommended Approach
All MCU hosted CC3100 systems Host MCU should own the task of monitoring VBAT to ensure it never drops below 2.3 V even under full load conditions.
Legacy Self-hosted, standalone CC3200 For legacy systems using SDKs prior to Service pack 1.0.1.6 and SDK 1.2.0 the CC3200 initialization sequence will turn on the internal network processor and may initiate Wi-Fi activity prior to application execution on the MCU. This can cause a sudden increase in the power supply loading. In these systems if there is a possibility that such loading can cause the supply voltage to sag below 2.3 V then the supply voltage should be monitored by a device external to CC3200.
New Self-hosted, standalone CC3200 For new systems using Service Pack 1.0.1.6 and SDK 1.2.0 or later then the CC3200 initialization will not turn on the internal networking processor function so the CC3200 application can start running prior to Wi-Fi activity. In such a scenario the application code can use the CC3200 ADC to monitor battery voltage but keep in mind that the ADC accuracy needs to be factored into any decision to enable or disable the NWP for normal operation. For more details on optimal detection and handling of consecutive resets owing to supply brownout to maximize system robustness see the last section of this document.

Other comments on circuit and software design: For systems requiring an external DC2DC power converter the TI TPS61029 may be worth considering.