CC2650 Using Power_setDependency(XOSC_HF);

Hi Tamir,

Tamir Dali said:

1. Were should I place this call, before what?, before GPTimerCC26XX_open, GPTimerCC26XX_setLoadValue

or it doesnt matter?.

The HF clock (running off the XOSC_HF crystal) is not immediately turned on after you set a dependency on it i.e. call Power_setDependency(XOSC_HF). You can either poll to check if the clock has been turned on or register a notification function that will be called once the clock is enabled. So, the answer to your question is that make sure the clock is turned on using the aforementioned approaches before you start using the GPTimers.

One way of determining if the clock has been turned on is by calling OSCClockSourceGet(OSC_SRC_CLK_HF) and checking the return value. If the return value is "OSC_XOSC_HF" then the HF clock is running. This is a driver lib API and requires inclusion of "driverlib/osc.h" header file.

Tamir Dali said:

2. Should I release the constraint after the Timer is no longer used via Power_releaseDependency(XOSC_HF);

It is a good idea to release the dependency once you no longer need the Timer. Leaving the dependency set may increase the power consumption as it takes longer to turn the XOSC_HF crystal on and off when the chip enters certain deep sleep modes.

Tamir Dali said:

3. What would be the affects of leaving this clock?. How would this affect my system?.

When the core goes into certain low power modes, the XOSC_HF clock will be turned off. If you need the clock to keep ticking, you would need to set a power constraint instead of a dependency. A constraint prevents the Power manager from entering certain low power states that disable the clock.

Best,

Ashish