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F28335 Low power modes

Dragan Warp
Prodigy 80 points
Other Parts Discussed in Thread: TMS320F28335, CONTROLSUITE

Hello,

I am using TMS320F28335 controlCARD and docking station. I want to test some features of F28335 MCU, like low power modes together with power consumption.

I tried examples from ControlSuite for low power modes, works well, expect I'm now sure what kind of external GPIO signal wakes up MCU from low power modes (Idle, Standby and Halt)?

I noticed that in Idle I can wake up on both raising and falling edge. From Standby MCU wakes up only at falling edge. And most interesting from Halt MCU wakes on pulse (high-low-high).

Is this true? Where are I can find more documentation about entering into and exit from low power modes on F28335? 

Regards,

Dragan

  • 0
    Guru 20525 points

    Hello Dragan!

    Did you go through these manuals carefully already?

    5758.TI_TMS320f28332-35_manual.pdf (p. 46,63,134);

    4442.TI_TMS320x2833x, 2823x System Control andsprufb0d.pdf (p.48,102).

    Regards,

    Igor

  • 0 in reply to Igor Gorbachev
    Prodigy 80 points

    Hello Igor,

    Thanks for your answer. Yes, I did.

    My main confusion is Halt mode. As I understand exit from Halt mode is the same as for the Standby (low signal at external GPIO (I call it falling edge in previous post)), but it's never said that external GPIO signal must go high after, and that only after going to high level MCU will exit from Halt mode.

    My first test is simple, I enabled pull up on GPIO1 and connected external switch to GPIO1 and GND. When in Standby immediately when I press switch (connect to GND) MCU wakes up. When in Halt and when I press and hold switch(connect to GND) MCU is still in Halt. When I release switch MCU wakes up.

    This is ok, when I use switch, but I want to use RC circuit and Schmitt triger, so I can periodically go into and wake up from sleep modes and measure average consumption, without manually pressing and releasing switch. Input of RC and schmitt is connected to other pin (GPIO2), so I can charge/discharge capacitor and output of schmitt trigger is connected to GPIO1 (wake up pin). I set GPIO2 instruction before going to sleep. On this way with RC and schmitt trigger I can only make edge (only one transaction from high to low) and it works fine with Idle and Standby, but I'm unable to wake up from Halt.

    So, my question is basically:

    For exit from Halt mode we need pulse (high->low->high)? Not only low signal (high->low) on external signal. 

    Regards,

    Dragan

  • 0 in reply to Dragan Warp
    Guru 20525 points

    Hello Dragan!

    If you will refer to fig.6-14 of F28335 Data Manual, then you will can see the following remark:

    D. When the GPIOn pin (used to bring the device out of HALT) is driven low, the oscillator is turned on and the oscillator wake-up sequence is initiated. The GPIO pin should be driven high only after the oscillator has stabilized. This enables the provision of a clean clock signal during the PLL lock sequence. Since the falling edge of the GPIO pin asynchronously begins the wakeup process, care should be taken to maintain a low noise environment prior to entering and during HALT mode.

    Thus for exit from Halt you need signal "high->low". But returning GPIOn state to "high" you can do only after a time interval "tw(WAKE-GPIO)" until the oscillator is stabilized. This interval is defined at the Table 6-18: tw = toscst + 2tc(OSCCLK) [cycles].

    Regards,

    Igor

     

  • 0 in reply to Igor Gorbachev
    Prodigy 80 points

    Hi Igor,

    Thank you for clarifying. I thought that you only need signal "high->low", and if you never go back to high tw time is infinitive, and oscillator is then definitively stabilized :) 

    Regards,

    Dragan