FiPy + Expansion Board: Battery Question
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@robert-hh Got it. Thank you again for this confirmation... I will take a look at SIM7020. I have been doing C/C++ for decades and C# the last nine years, but somehow I am really fond of this primitive puppy MicroPython - never wrote a firmware before with C... so it will be a factor...
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@securigy indeed as things stand waking up from deep sleep every few seconds is just not a possible scenario.
For the LTE side of things, that’s where PSM/eDRX should come into play. They allow the modem to be in a low power state but still be considered connected to the network, so when you have something to send you just wake up the modem, send, and put back the modem in low power mode. However IIRC (never tried it myself, but saw discussions on the topic) there are still issues with this in the FiPy. Note that even if supported by the FiPy, it also needs to be supported by the network, I’m not sure this is available everywhere.
Also, to send a position every few seconds, your GNSS chip will need to remain in a relatively high power state as well. Depending on the chip and what accuracy and interval you need there may be power saving modes, but it’s always a compromise, reducing power will mean reduced something else (nothing comes for free).
An alternative is to make sure you send data only if you actually move, do you can remain in deep sleep when the device is idle. You can use an accelerometer to wake up, or a vibration sensor. There are challenges with this as well, see relevant discussions on the forum (there was one on this topic a few days ago).
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@securigy I just tested a generic ESP32 with the WiPy3 pycom firmware. The standby current is 35 mA, going down with machine.sleep() to 4 mA, including the USB/UART bridge. That is a very good figure! machine.sleep() keeps the machine state, so wake-up is immediate.
With an FIPY, the current at machine.sleep() with LTE enabled stays at 100mA, while teh ESP32 alone consumes almost no power at sleep(). -
@jcaron You are absolutely correct on all points: I jest read yesterday that ESP32 has ULP (Ultra Low Power mode) so it makes sense that FiPy will have something like that as well... another field for me to research. But for now I assume that I will not be using deep sleep.
About detecting motion: really good point - however my FiPy sits on Expansion Board 3.1 that I believe does not have accelerator...another hurdle...Meanwhile, I did discover something useful that will allow me to experiment with mAh consumption with ease.
Check this thread:
https://forum.pycom.io/topic/5694/measuring-amperage-consumptionBTW, I am using GNSS Click 5 from uBlox with NEO-M8N with cold start of under 30 sec.
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