AM335x Starter Kit TMDSSK3358 RTC

Wayne Richmond

Prodigy 190 points

Is it possible to connect a battery to the TMDSSK3358 board to battery backup the RTC only ?

If so, where do the connections go and what battery is suitable ?

Thank you

Wayne

over 11 years ago

0 Vidin Tsonev-XID over 11 years ago

TI__Intellectual 1340 points

Hi,

According to the schematic of TMDSSK3358, the VBACKUP supply pin (pin27) of the PMIC is hardwired to VCC5 (VBAT in this case) and no backup battery option is provided (check TP5).

Board design files you can find here:

http://processors.wiki.ti.com/index.php/AM335x_StarterKit_Board_Design_Files

and PMIC datasheet (backup batteries supported are described here)

http://www.ti.com/product/tps65910a3

Best regards,

Vidin

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Hi Wayne,

This cannot be done without modifications to the board. You can find the SK schematics here: http://processors.wiki.ti.com/index.php/AM335x_StarterKit_Board_Design_Files. A battery should be attached to PMIC pin 27 (VBACKUP), but in the SK this pin is already connected to the input voltage VBAT, so this connection would need to be cut (I don't know if it's physically possible). Then it depends on the AM335X silicon revison you have on your SK board - if it's Rev.1.0 there is no much use to add a battery due to Errata issues and big consumption.

0 Wayne Richmond over 11 years ago in reply to Biser Gatchev-XID

Prodigy 190 points

Hi,
Yes, I looked at the schematic and wondered if we could isolate the "RTC LDO" U21 by removing R121 and then connecting VRTC to our own power source/Battery!

Any thoughts on this?

How do I find out what AM335X silicon revision I have?

Cheers,

Wayne

0 Biser Gatchev-XID over 11 years ago in reply to Wayne Richmond

TI__Guru**** 393215 points

Keep in mind that VRTC has to be strictly 1.8V +/- 5%. And how are you going to charge the battery?

Device package markings are described in section 1.2 of the AM335X Errata, Rev.E.

0 Wayne Richmond over 11 years ago in reply to Wayne Richmond

Prodigy 190 points

We have come up with another option. We are getting the DS3231MPMB1 Peripheral Module. This is an I2C Date/time module which almost (but not quite) fits in to the I2C expansion connector of the Starter Kit. It has provision for a Lithium battery.

Looking at the Linux menuconfig there is a driver for the DS3232 chip. I am hoping that this uses the I2C expansion bus of the Starter Kit and it will all just work ;)

If anyone has any info on this, preferably ways to make it work if it is not as straight forward as I hope, then please reply.

Thank you,
Wayne

0 Vidin Tsonev-XID over 11 years ago in reply to Wayne Richmond

TI__Intellectual 1340 points

Hi,

In the latest SDK the RTC drivers are located in this folder:

<your path>/ti-sdk-am335x-evm-06.00.00.00/board-support/linux-3.2.0-psp04.06.00.11/drivers/rtc.

There is rtc-ds3232.c and rtc-ds3234.c that could be useful if these devices are similar to DS3231.

BR,

Vidin

0 Wayne Richmond over 11 years ago in reply to Vidin Tsonev-XID

Prodigy 190 points

Thank you for that, it will be most helpful.
It does look like it should all just slot into place :)

As for the revision, although a slight discrepancy in the markings I am reading mine as 1.0
"AM3358ZCZD72"
"2AARQW G1"

My kits are relatively new, just received one today and I do understand that kits like these could be sitting in stock for awhile, especially when order from a third party like mine. just a shame it is old revision. Are Ti using the new revisions yet. I didn't check to see when 2.0 or 2.1 were released.

Yes, I have seen the issues regarding using a battery for the RTC on this revision so using an external clock may be the best option.

Anyway, thank you for all your help,

Wayne

0 peaves over 11 years ago in reply to Wayne Richmond

TI__Guru 63125 points

The Revision Identification section of the AM335x Data Sheet provides more detail than the AM335x Silicon Errata, which should help identify your device as silicon revision 1.0.

Regards,
Paul

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AM335x Starter Kit TMDSSK3358 RTC