Hi - I have a wearable sensor project, battery powered. For reasons of packaging the device MUST use a LIR1632 coin cell (30 mAh). It would be great if the MCU is sleeping most of the time, then wakes to take analog measurements every 60 seconds, then returns back to sleep. Every 5 or 10 minutes, I want to power up BLE and transmit all the readings. I've have been playing around with the Seeed XIAO BLE (sense). There are some really nice features in their package. I'm having problems, however, finding a way to achieve low power and BLE by just using the Arduino IDE and appropriate libraries. The Arduino nano is too large. Should I be looking at other boards? Or should I keep trying to get everything I need out of the Seeed XIAO? Thanks for any replies.
30 mA from a coin cell? Did You check their specifications? How often is it okey to change the cell?
Does the BLE transmitter run on such low current? I doubt it.
30 mAh, not 30 mA. There is no mention of how long the 30 mAh has to last. If they can get the average current draw down to 1 mA they could get 30 hours out of the cell.
What are those problems? The XIAO BLE (Sense) product page claims "Standby power consumption is less than 5μA".
When transmitting at 8 dBm, the radio alone will draw about 30 mA, add a few more mA for the CPU and active peripherals.
Which of course is the bane of every battery powered project ... the limited power source that has inconsistent specifications between manufacturers:
IMO, if @jremington's transmitting power @ 30mA is correct then from the Op's requirements, there are 2 power budgets that must be calculated:
As the LIR1632 is rechargeable, can this device sit on an always on charger and just be removed from the cradle for use when needed? Maybe 2 cells in parallel?
The 30 mA figure came from Nordic DevZone: nrf52840 max current consumption? - Nordic Q&A - Nordic DevZone - Nordic DevZone
Of course the TX power can be reduced programmatically, 0 dBm is popular, but with lower range.
Thanks jremington. You are correct in stating that the Seeed Studios website claims a microamp standby power consumption. But that is only achievable when one loads the version 1.0.0 board firmware into the Arduino IDE. With that board I can't seem to access BLE functions at all. Alternatively, you can update to the 2.6.1 Seeed Studios version and get BLE to work, but the current draw is much higher. There is pretty good discussion about this in the Seeed Studio forums, but those are not as well attended as this Arduino forum.
Although I did not provide a range for this project, I'm fine with a range of about 6 feet as the device is just sending its packet to a phone held by the same person wearing the device.
In low power mode (board firmware version 1.0.0), I find that the Seeed XIAO draws 30-50 microA when performing ADC functions. My analog sensor draws about 4 microA. I have found threads in the Seeed Studio forum where people have claimed some BLE function that increases the current draw to 300 microA, that seems pretty decent to me. I should only need the BLE for millisecs every 5 or 10 minutes. Overall, I'm trying to achieve 7 days between battery recharge. If I can squeeze 14 days even better. But I'm happy to dig into battery optimization later in the project, at this point I'd be happy to achieve just a few days of life from a single charge.
Do not confuse average current draw with peak current draw. Most hobbyists are not set up to make those sorts of measurements, so treat what you read on the forums with skepticism.
What you are trying to do is typical for development of a commercial product, by a company with a research budget, a few highly trained and experienced EEs, working in a fully equipped Research and Development lab. All possible corners are cut to maximize battery life, while achieving the stated goals for the product.
And it sounds like you can't believe the claims that Seeed Studio is making for its products.
I understand. We'll have a scope on the current draw soon in order to capture the peak draw and model the power budget much more accurately than the numbers that I have shared on the forum. Thanks. And yes I'm super skeptical of the values reported by Seeed Studios and what can be found on their forum. Any advice on another board to look at? 
Sorry, no, but I'll be interested in what you find out about the XIAO using a decent scope.
My mistake. Fiddling with the phone in a noisy environment..
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