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I'm working on a project that will (hopefully) go 30 meters below water and to achieve this, I'm thinking of potting the entire electronics assembly.

Charging will be done via induction and comms via BLE.

Power on and off can be achieved with a magnetic switch, but where I'm confused is with the reset.

According to the artemis documentation, every time the device is powered off, a reset is required to wake it from deep sleep. That means I would need a separate switch for rst?

Is there a way to avoid needing this reset? I just want the device to log when powered on.

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Found the solution (I believe) in the artemis hookup guide (I think):

Stop Logging and Reset Buttons

One of our favorite ways is to connect up external “stop logging” and “reset” buttons to the RST and pin 32 breakout pins. If stop logging has been enabled using the configuration menus, pulling pin 32 to GND via a push-to-close button will gracefully stop the logging and place the OLA into deep sleep. Pulling the RST pin to GND will reset the Artemis, waking it up again and logging is restarted. We like this method because the log file on the SD card is closed gracefully, making sure that no data is lost. You can think of the pin 32 and RST buttons as “Off” and “On” buttons. When “Off”, the current drawn from a LiPo battery will be no lower than 80µA because the 3.3V regulator is still enabled.

PSWC Pins

As we described above, the PSWC pins can be used to disable (switch off) the OLA’s 3.3V regulator. Connecting the pins together via a SPST toggle switch pulls the regulator’s EN pin low and disables it. This causes the 3.3V rail to collapse. If the Artemis is running, the voltage supervisor will generate an interrupt to immediately put the Artemis into deep sleep. Because the 3.3V rail has already collapsed, the Artemis cannot close the log file on the SD card gracefully. The OLA syncs the log file regularly while it is logging, but there is a small risk of data loss if you use this method to disable the OLA.

A better method is to use a “stop logging” button as described above. Pressing the stop logging button will gracefully close the log file and place the Artemis into deep sleep. Then you can disable the regulator safely via the PSWC pins. In this state, the OLA will draw less than 1µA from external power or LiPo battery, the RTC battery will provide the 18µA needed by the Artemis to keep its RTC running.

The Artemis will stay in deep sleep when you toggle the regulator back on again. You will need to reset it via a reset button to start it logging again.

[tomts]

In my experience, a power off, then on is a reset. Even in deep sleep mode, if power is cycled, the code starts over at the top normally. There is no need to set up a separate reset button.

[PaulZC]

Hi tomts,

Sorry, that is not correct - in this case. The Artemis goes into deep sleep when external power is disconnected - and remains powered by a small on-board battery. This allows the Real Time Clock to keep running. To bring the Artemis out of deep sleep, it is necessary to press the reset button.

"The Artemis will stay in deep sleep when you toggle the regulator back on again. You will need to reset it via a reset button to start it logging again."

Best wishes,
Paul

[tomts]

That makes sense. I wasn't aware of the RTC battery.