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在MSP432P401R RTOS中，如何将clock source由Clock System改为 WDT_A (in interval timer mode) ?

Gilbert
Expert 1048 points

1. 目标是在MSP432P401R RTOS中，实现空闲时低功耗，使电流小于3uA，故选择了LPM3。

2. 但是，在LMP3中，Clock System是失效的，也就意味着RTOS中的计时器clock都是无效的。

3. 考虑到WDT (in interval timer mode) 在LPM3中可用，能否令RTOS中的clock引用WDT_A？

  • 0
    TI__Guru**** 252096 points
    根据您的描述，您应该是想在LPM3下继续使用定时器且保持空闲时低功耗？您可以参考下面的文章

    processors.wiki.ti.com/.../TI-RTOS_MSP432_Timer

    The basic idea is to use the watchdog timer to drive the TI-RTOS' Clock tick. This is accomplished by the following steps.

    1 Tell TI-RTOS that the Clock tick will be driven by the application. This is accomplished in the TI-RTOS configuration file (.cfg).

    2 Create a Hwi for the watchdog timer. This can be done during runtime execution or via the TI-RTOS configuration file (.cfg). For this example, we'll create it in the configuration file.

    3 Enable the watchdog during runtime.

    4 Restrict the DEEPSLEEP_1 (aka LPM4) mode, otherwise the watchdog is deactivated when entering that mode. The power savings between DEEPSLEEP_0 and DEEPSLEEP_1 is small.

    5 Have the Hwi function call Clock_tick() to drive the Clock modules internal timing.
  • 0 回复 Susan Yang
    Expert 1048 points

    谢谢您，这正是我想要的!

  • 0 回复 Gilbert
    TI__Guru**** 252096 points
    很高兴能帮到您！
  • 0 回复 Gilbert
    Expert 1048 points
    经过实测，将Clock.tickSource设为Clock.TickSource_USER（WDT_A）后：
    当Clock.tickPeriod = 250.000ms，电流是 12uA；
    当Clock.tickPeriod = 15.625ms，电流是 41uA；
    当Clock.tickPeriod = 1.953ms，电流是256uA；
  • 0 回复 Gilbert
    TI__Guru**** 252096 points
    谢谢您的反馈！能说下您测量的步骤吗？现在还是不符合您的要求？
  • 0 回复 Susan Yang
    Expert 1048 points
    先不说电流的问题，目前令我比较难受的有两个问题：

    问题一，tickPeriod = 250ms，之前使用Timer时，tickPeriod = 1ms，差异太大。我程序里的所有Task_sleep()输入参数需要重新计算，且无法显示小于250ms的计时；

    问题二，在执行UART_read()时，Task进入blocked状态，整机会触发进入LPM3，而在LPM3中，EUSCI_A会失效；这样，UART_read()只能超时退出，且收不到任何串口数据；
  • 0 回复 Gilbert
    TI__Prodigy 430 points

    能不能搞个任务就用来进出低功耗，用RTC或者watchdog timer记时。clock不变。这样就能保证有一段时间MSP432能进LPM3。