Realtime Clock Question

Hello all,

I need a relatime clock working on my project, the clock need to be working since the board is off, are there a circuit to control this?.

I’m looking for information about realtime clock, I didn’t see anything about batteries operation, or sleep mode, there is an option to use batteries to mantain the realtime working?

Regards,
Alexandre Davi

On the Beagle, if you turn it off, you turn off the RTC. There is no battery backup on the Beagle. You would need to Mount an external battery backed RTC via the expansion connector.

Gerald

I need a relatime clock working on my project, the clock need to be working since the board is off, are there a circuit to control this?.

I'm working on one. It will be also be possible to wake the Beagle up at a pre-set time.

Stuart,

That’s very interesting. Any idea what the current draw of the board will be when it is in sleep mode and how long will it take to come out of sleep mode?

Steve

It depends on the kernel, how low you need to be, and other factors. The sleep modes available in the OMAP3 are very flexible. If you want the board to boot immediately or pick up where you left off, then the 1.8V will need to be active to keep the memory contents. The OMAP3 can be put into various modes anywhere from low frequency and low voltage with the ARM active, to everything shutdown except the PRCM. I suggest you read up on the capabilities in the OMAP3 Technical Reference Manual.

Beagle does not support shutting down the 3V rail, so the DVI-D framer will always be active, but can be put in low power mode with the enable signal. The serial port drivers will always be active as well. You can shutdown various power rails from the TWL4030 as well. In power down mode the VBAT regulator will be active as well. It is not possible with the Beagle design to meet the lowest possible current mode ofr sleep as the HW is not set up for it. But, you should be able to get to a low current point by working with the OMAP3 and the regulators in the TWL4030.

The best bet is to invoke frequency and voltage scaling and turn off whatever you don’t need inside the OMAP3.

Gerald

Steve Gulick wrote:

That’s very interesting. Any idea what the current draw of the board will be when it is in sleep mode and how long will it take to come out of sleep mode?

Dont know yet, but not much. Its just at the R&D stage at the moment. I haven’t even got a Beagleboard yet!
What I can say is, that it’s a PIC that beagle can talk to though the serial port on the expansion socket. Its designed for a vehicle, so when the ignition goes on, a relay is activated to power beagle (2A DC-DC converter). The PIC keeps the relay on until software on beagle says it can shut down.
It will also provide a crystal controlled realtime clock.
Plus other features I have in mind.

If anyone wants to help, they are more than welcome.

Stuart.