Hello Everyone,

I'm trying to add an RTC backup battery to Vbat pin of the microcontroller inside an LED lamp controller, because, when there's power outage, the controller is basically crippled due to reset RTC.

Unfortunately, as can be seen in the photo, MCU's markings are wiped out, and the external xtal (probably 32.768 kHz) is connected to (double checked already) pins 45 and 46 which is another oddity; to my limited knowledge, very uncommon, or I'm unable to identify pin #1 correctly.

Any inputs or hints are appreciated.

 

Hello,

The maker likely obscured the markings, so that no copy or modification can be done.
There are some lands on the side of the board.
They are likely there to program the chip.
You could try to find out what the connections on the chip are.

Bertus

 

Hello,

The maker likely obscured the markings, so that no copy or modification can be done.
There are some lands on the side of the board.
They are likely there to program the chip.
You could try to find out what the connections on the chip are.

Bertus

Thanks Bertus. I'll try it.

Any idea about pin 45 and 46 where the xtal is connected? I went through many data sheets including a few Chinese ones, and in none was xtal connected to pins 45 and 46; mostly connected to pins 3 and 4. Could it be that pin #1 identifier dot is purposely displaced?

 

How do you know it is an oddity?

 

How do you know it is an oddity?

Hi atferrari
Because, I went through a handful of datasheets. But, you're right, I can't be sure 100% it's an oddity, because, I'm not knowledgeable enough about MCU's. Cheers

 

Any idea about pin 45 and 46 where the xtal is connected? I went through many data sheets including a few Chinese ones, and in none was xtal connected to pins 45 and 46; mostly connected to pins 3 and 4. Could it be that pin #1 identifier dot is purposely displaced?

You're probably going to have better luck starting with power connections. I don't know about all micros, but I do know with PICs every one has at least one set of pins for a timer crystal in addition to the main crystal. It's entirely possible the micro is running off an internal clock and using the external for RTC timing only.

 

Only chip/micro I can find with any sort of XTAL input to pins 45,46 is the Ti series of:
MSP430FR5994, MSP430FR59941, MSP430FR5992, MSP430FR5964, MSP430FR5962

where those pins are defined as LFXIN and LFXOUT in the RGZ package, which are designed for low frequency crystals...

But, those seem a bit overkill for such a device....

 

Thank you all including Sagor and Geekoftheweek... . All your inputs are highly aporeciated. I've already contacted the manufacturer waiting for reply. Cheers