LOW POWER MODE for KL25Z USB MSD DEVICE

[charanreddy]

Hi,

can we use low power mode in kl25Z USB MSD ...?. If yes, then how to make the CPU to come out of Low power mode after inserting the device in to the Host.

Regards,

Charan

[mjbcswitzerland · Accepted solution]

Hi

USB is "operational" only in RUN and WAIT modes and not in (very) low power modes.

However you can use very low power modes when you don't need USB operation and detect a USB host connection by connecting the USB +5V to a LLWU input (with suitable circuit). The device can then be woken by detecting this voltage being attached and operate in RUN/WAIT modes until it may be set back to a low power mode again.

Regards

Mark

Kinetis: http://www.utasker.com/kinetis.html

KL25: http://www.utasker.com/kinetis/FRDM-KL25Z.html / http://www.utasker.com/kinetis/TWR-KL25Z48M.html

LLWU: http://www.utasker.com/kinetis/LLWU.html

For the complete "out-of-the-box" Kinetis experience and faster time to market

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[charanreddy]

Hi Mark,

Thank you very much for your quick replay.

While doing this i came across "USB Transceiver Control Register 0 (USBx_USBTRC0) " in the KL25Z data sheet. Is it required to use this register if i am fallowing the above method mentioned by you. I am a bit confused by the reading the description of the "USBx_USBTRC0" register.

Regards,

Charan

[mjbcswitzerland]

Hi

USBx_USBTRC0 is used to command a reset to the USB controller. It is generally used when configuring USB but won't necessarily be required to control low power operation or to recover from it. In low power mode all clocks to the USB controller will be stopped.

Regards

Mark