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UnexpectedMaker / esp32s3

Assorted files for my ESP32-S3 development boards
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FeatherS3 pins for external 32.768kHz crystal #14

Closed rottaran closed 1 year ago

rottaran commented 1 year ago

While doing experiments with BLE on battery power, we noticed an unexpectedly high current consumption. This makes the battery connector on the board less useful. With dynamic frequency scaling, modem-sleep and CPU pause, we got down to 25mA average. In order to get to the 2 to 5mA light-sleep mode with running BLE connections, it is necessary to connect a 32.768kHz crystal and respective load capacitors to the XTAL_32K pins.

Sadly, the XTAL_32K seem to be not connected on anything on the UM Feather S3. Maybe it could be a nice feature for future products to at least have unpopulated footprints for the crystal and capacitors on the bottom side of the board.

UnexpectedMaker commented 1 year ago

Sorry I didn't get around to answering this already :( IO15/16 that are used for hooking up an external 32K Xtal are already in use on the second STEMMA/QT connector as I2C bus 2, sorry.

rottaran commented 1 year ago

No problem. I was unaware of the change back then. Seems sensible to separate both I2C busses. Out of curiosity, what speaks against using IO17/IO18 or IO45/IO46 for the STEMMA2 connector?

UnexpectedMaker commented 1 year ago

Well, IO46 is a strapping IO, so not usable, but ultimately, nothing wrong with other IO for STEMMA2 - but 15/16 is what I chose and it can't be changed now as it's a released design with supporting firmware that initialises those pins as STEMMA/QT #2.

I do custom design work for people needing alterations on my designs - If an external 32k Xtal is something you'd like and it's something you require in quantity, I'm happy to chat about it.