Does the pocketbeagle have the external 32khz oscillator necessary to have the RTC working in suspend and suspend to ram modes? If not are there pins on the header to which one can be soldered?
I do not think the crystal is included and not sure what pins are needed. Perhaps check the Black’s schematics.
I checked it but I didn’t understand it. I saw one crystal, a 24mhz one. I couldn’t tell if that was the required xtal or not, or if the OSM335x-SM module even has those pins exposed on the BGA.
The schematic I found shows that the RTC pins are not connected to anything
The pins don’t seem to be tracked out to the headers so looks like you are out of luck in using the internal RTC.
If I’m out of luck with the internal, what solution could I use to implement things like a sleep to memory or total shutdown until RTC alarm? I.e what chip or board exactly.
Are you looking to go into a low power mode, or just get accurate time when NTP is not available?
There are small boards with RTC on them that are easy to use.
If you have a spare GPS receiver, you could also use that for getting the time.
Both Low power mode and accurate time when NTP is not available. The device was/is to be used to monitor the temp of a freezer. The time needs to be accurate to the minute; which is why when I send the data to the server, I programmed it so that the server will input the time that it was received. However if there is a break in the communications, I wanted the system to cache the messages. This however requires an accurate time on the device, because I won’t be able to get the database server’s time.
I can get an ESP32 to be an RTC Alarm for $8 dollars; and I know that has RTC wake up. I’ve tested it using nanoF.
Adafruit has various breakout boards with RT clocks on them: https://www.adafruit.com/category/858
…all without an RTC Alarm function. The alarm is the most important thing.
Many of the DS series from Dallas (Now Maxim) have alarms you can set and then the interrupt line can be used to wake up your device.
I think I know why the OSC pins weren’t broken out. If they were then there would be no reason to buy the raw chip. It’s the same reason why there are no screw holes, the board is not intended for commercial products, it is intended for hobbyists. I suppose that harvesting the SIP, re-balling it and adding it to a different board costs less than 25 bucks to you… btw the BeagleBone blue has the xtal on board.