Argon Sleep questions

Firmware Device OS
1

I’m trying to do a small weather station project with an Argon and a 1000mah LiPoly battery. That part is relatively easy. However, given that the Argon can only STOP, not HIBERNATE for the RTC change, I have some concerns about my peripherals.

In STOP, does the 3v3 line turn off from the Argon? I’m using the 3v3 output to power my two thermometers, and I believe in HIBERNATE, that line would turn off. I’m still waiting for my solar assembly to show up so I can’t test, but I thought I would ask. Should I put a NPN in front of the power to the thermometers, or will it work without vampire draws if connected directly to 3v3?

Also, I don’t see any figures for how much current is consumed by the device in STOP versus HIBERNATE. Is that available somewhere and I missed it? I have been reading a lot of the posts about sleep issues with Argon/GEN3 devices, and it looks like if you manually turn WiFi off, the sleep current goes below a milliamp, but I’m curious if there are any actual measurements that can be found?

2

Nope, the 3V3 regulator stays on which draws some current itself. This is why there is the EN pin to turn OFF the regulator and thus the entire Argon. However, typically, this pin would need to be controlled with an external timer.

No again, see above.

You could if you are concerned about the current the thermometer draws while powered.

There isn't any official documentation I believe. For the nRF52840 itself, the power difference is only about 20-40uA. However, it is the 3.3v regulator that draws the most current in sleep mode and I can't recall what that is.

Many members have used an external timer or event a Tiny85 processor to set the EN pin low for a fixed or programmable time. They also use it as a watchdog timer to prevent software lock-up.

3

Thank you, pretty much what I thought. Is the BATT input the same as the 3v3 line? Does the EN pin control both? I’m doing this with a battery connected to the battery terminal via a SparkFun Solar battery management board.

4

@peteb, which "BATT" pin would that be? Are you referring to the Li+ pin which, as per the docs is:

This pin is internally connected to the positive terminal of the LiPo battery connector.

Also, the 3v3 line, again as per the docs is:

This pin is the output of the on-board 3.3V regulator.

It cannot be used as an power input on the Argon.

The EN pin powers off the entire board except the battery charger.

5

Sorry, I’m used to the Photon, this is my first pass with the Argon in any serious capacity so I still associate with that board. Yes, the LI+ pin, so thanks for the reference.

I’m going to put a couple of transistors in front of the peripherals for now. Will look into an RTC to do this if that turns out to be inefficient.

Any suggestion on a good cheap RTC that would work here based on experience? I think the DS3234 will work, but it’s a bit of overkill for this. I can’t figure out if the 1307 based on the ones I can buy cheap with a PCBA will do an interrupt, and the library doesn’t seem to support an interrupt based on time.

6

@peteb, you can take a look at @rickkas7’s RTC design here:

You can also find some fine members who have worked with the Tiny85 and would likely share their code.

7

Thanks, I found a Mikroe board with that chip that I believe will work. I really wanted the Photon sleep capabilities to avoid having to do a lot of work on state (run setup everytime). I had considered just waking up from sleep and rebooting the chip to do this, and may test it anyway. But simply turning the system off and then waking up with an external RTC may be the best choice.

My HW comes tomorrow, will start testing this weekend.

Thanks for all the help.

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8

A small correction here, while this is true for the Boron it's not for the Argon.
On the Argon (and Xenon) the 3v3 pin can be used as 3.3V input but you need to avoid parallel powering via USB and/or LiPo and the EN pin should be tied to GND.

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9

Thanks for the correction @ScruffR. Seems though I selected the Argon in the docs, I got the Boron documentation pages. @peteb, to be specific, the documents says:

3V3 PIN

This pin is the output of the on board 3.3V step-down switching regulator (Torex XC9258A). The regulator is rated at 1000mA max. When using this pin to power other devices or peripherals remember to budget in the current requirement of the Argon first. This pin can also be used to power the Argon in absence of the USB or LiPo power. When powering over this pin, please connect the ENABLE pin to GND so that the on board regulator is disabled.

This means that the EN pin no longer "turns off" the Argon, leaving that to you and the 3v3 power source being supplied to the 3v3 pin.

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