Does the radio module stays active during watchdog.sleep() ?

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Post Reply
User avatar
raghavrathi
 
Posts: 13
Joined: Wed Apr 20, 2022 2:12 pm

Does the radio module stays active during watchdog.sleep() ?

Post by raghavrathi »

Hi, I am using a Adafruit Feather M0 RFM95 LoRa Radio and I am trying to put the receiver to sleep. I was suggested to use watchdog.sleep(). Is it possible that the radio module keeps listening during watchdog.sleep()?
I am doing some experiments in which I am transmitting some LoRa trace with certain intervals, and I am making the feather go to sleep a little before the transmission on the signal, but some how the feather is still able to receive the messages.
Any help is appreciated.

Thank you.

User avatar
adafruit_support_mike
 
Posts: 65032
Joined: Thu Feb 11, 2010 2:51 pm

Re: Does the radio module stays active during watchdog.sleep

Post by adafruit_support_mike »

raghavrathi wrote:Is it possible that the radio module keeps listening during watchdog.sleep()?
Yes. The radio is separate from the microcontroller, and watchdog.sleep() only controls the microcontroller.

The radio module has no sleep mode, and the only way to reduce its power is to shut down the whole Feather, pulling its EN pin low.

If you want the Feather to wake up periodically, you might want to consider the TPL5111 low-powr timer:

https://www.adafruit.com/product/3573

It can control the Feather's EN pin, turning the board on at intervals you can select, from 10ms to 2 hours. The Feather can boot, do anything it needs to, then aend the TPL5111 a DONE signal that will shut off power until the next wakeup time.

The TPL5111 breakout uses about 20uA while it's counting, almost all of which is leakage current through the power-on LED. If you cut the trace to the LED, the breakout uses less than 100nA.

IIRC, the shutdown current for the average Feather is around 80uA, so the cost of running the TPL5111 would be negligible.

User avatar
raghavrathi
 
Posts: 13
Joined: Wed Apr 20, 2022 2:12 pm

Re: Does the radio module stays active during watchdog.sleep

Post by raghavrathi »

That's interesting to know. I will probably get the low-power timer then. Thank you

User avatar
TI545
 
Posts: 58
Joined: Tue Feb 27, 2018 5:25 pm

Re: Does the radio module stays active during watchdog.sleep

Post by TI545 »

Ah. I really like this suggestion. I would never have seen this low-power-timer while wandering thru the adafruit site. Simple and effective. I’d say it hitting a problem with a hammer, but since Andreas Speiss taught me that the ESP32 sleep mode reboots he chip, you might as well use this.

User avatar
adafruit_support_mike
 
Posts: 65032
Joined: Thu Feb 11, 2010 2:51 pm

Re: Does the radio module stays active during watchdog.sleep

Post by adafruit_support_mike »

There are a lot of microcontrollers that have good low-power modes, even into the nanopower range, but getting a 32-bit microcontroller to suspend and resume operation is more involved than 'flip a switch and It Just Works'. There can be issues with sequencing power domains, and there are definitely issues with restarting and syncing multiple clock domains. There was a period where the ESP32 firmware had a glitch in the resynchronization of the I2C peripheral during wakeup.

Beyond that, low-power design is a system design problem, not just a hardware or software problem. Beginners in the field are usually surprised by the by the amount of battery power lost to capacitor leakage and humidity adsorbed to the surface of a PCB exposed to air. Simply blowing across a PCB can create 10nA of leakage through electron capture by air molecules moving past exposed conductors. It takes specialized techniques to maintain resistance higher than about 40M (25nA/Volt).

None of our boards are designed for that domain. Most Feathers manage 80uA to 90uA when the voltage regulator is shut off. You can reduce that with a TPL5110 which controls power to the load, but even there my candidate design used a 2-mosfet power switch common in subthreshold (low nanoamp, high picoamp) mosfet designs. The cost of suitable mosfets and PCB space didn't survive the "will enough people pay for this feature to justify the price?" test.

User avatar
raghavrathi
 
Posts: 13
Joined: Wed Apr 20, 2022 2:12 pm

Re: Does the radio module stays active during watchdog.sleep

Post by raghavrathi »

Thank you for the details, learning something new everyday.

Post Reply
Please be positive and constructive with your questions and comments.

Return to “Feather - Adafruit's lightweight platform”