User manual

GHI Electronics,LLC Embedded Master User Manual

Hardware and Software Library

11.17. Power Control / Sleep

Hibernate is supported to save power. In this mode all clocks are stopped. This feature

should be used by advanced users only. The user must disable peripherals such as USB

Device and CAN before hibernating and re-enabling them after waking up, as needed.

LPC24xx data sheet should be used as a reference.

Hibernation mode is entered by calling Utility.HibernateSystem() then the processor will only

wake up as the user specified. For example, in order to wake up on a button press

connected to a GPIO pin, the pin must be defined as interrupt port and INTWAKE register

must modified before sleeping. Likewise, registers can be directly modified to tweak the

sleeping mode operation.

Utility.HibernateSystem() first sleeps the processor (Power-down mode in PCON register,

refer to LPC24xx datasheet), and after waking up, it resets all clocks including

USBCLKCFG, then control is returned back to the user.

Normal power operation is about 160mA. In hibernate mode, it is about 40mA.

Example

// Before sleeping

INTWAKE.Write((1 << 7) | (1 << 8)); // wake on GPIO0, GPIO2 activity

// define an interrupt pin to wake up the processor on the rising edge (on button

release)

InterruptPort DownBtn = new InterruptPort(EmbeddedMaster.Pins.E0x, true,

Port.ResistorMode.PullUp,Port.InterruptMode.InterruptEdgeHigh);

// sleep, Press and release Down Button to wake it up.

Microsoft.SPOT.Hardware.Utility.HibernateSystem();

// User can resume operation now

A full project example is provided with he SDK.

Hibernate_GPIO_Wakeup and Hibernate_USB_Wakeup projects.

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