Remote data monitoring: LoRa + nRF5, STM32WLE, ...?

[Finderbinder]

I need to monitor/collect temperature data (maybe other ambient data lately). Wires just do not fit. So I think battery powered LoRa is the way to go.
At first I hooked up on SX1262, but it is RF part only, so also mcu would be needed.

So here are more questions: which ultra efficient mcu? Energy efficiency matters. Programming friendliness matters. Communities matters.
Atmega/Attiny are out of the game?

So maybe mini modules with SX1262+nRF52840, or STM32WLE5CC, or ...?

It would be nice to choose a right direction (time, money, nerves economy).

[liaifat85]

For remote data monitoring you can consider ESP32. It's possible to read sensor data remotely with firebase using ESP32. This is how to  Read Data from Firebase Database with ESP32.
https://www.theengineeringprojects.com/2022/03/reading-data-from-firebase-database-with-esp32.html

[Finderbinder]

I guess ESP32 is less battery friendly, no?
To change battery once a month is not acceptable, once a year is acceptable.

[Buriedcode]

You're gonna need a power budget based on what battery you have in mind.  Band, range, and sensor update period are all determined by your available power.

[Finderbinder]

You're gonna need a power budget based on what battery you have in mind.  Band, range, and sensor update period are all determined by your available power.

Somewhat button cell would be nice, but a few AAA or AA batteries are acceptable too. I think update period of 1 min would be good. 868MHz. Distance from sender to receiver would be mostly in tens meters around house (inside and outside) and few senders as far as 500m in town... and one sender 7km away (just for fun, if possible).

[uer166]

Those distances imply LoRa. Current-wise: 10mA during continuous receiving, and 100mA transmitting at reasonable power at 3.3V.

With minute update a coin cell probably won't cut it.

[Finderbinder]

And what about mcu to complement it: nRF52840, STM32WLE...? Someone can recommend one?

[dobsonr741]

How often are you sampling the temperature, etc. and how often transmitting?

You do not need to power your sensor rig between measurements and transmission, you can cut power completely and have only an RTC or a wake-up device consuming battery constantly. You can be under 1uA with the right choice.

[Finderbinder]

How often are you sampling the temperature, etc. and how often transmitting?

As I mentioned above, I think 1 time per minute (sampling and transmitting) would be nice.

[mayor]

I think you might find what you need with TI's CC family (CC1312 here?). Support is excellent, low power, good range, MCU is integrated with radio, and despite having some issues, development environment is good.

[selcuk]

If it is possible to use two different designs in the project, I can recommend to use nrf52810 + pcb antenna + sensor + battery to have energy efficiency, low cost and BLE connectivity for indoor devices. You need to use a BLE + lora or BLE +  wifi etc. on a ESP32 or similar to connect to the device 7km away and to the indoor devices. It is a little complicated for software and system design but energy efficiency and cost will be better. And you have the possibility to connect indoor devices with your phone. I don't have lora experience so I cannot recommend a MCU for that.

[Tation]

Xiaomi thermometers (Bluetooth LE) use a Telink TLSR825x MCU and can run for a year with a single CR2032 cell.

Such Telink chip is also Zigbee and BLE Coded (long range) capable. There are alternative firmwares for them available in Github, maybe you may want to take a look for some fast experiment...

https://github.com/pvvx/ATC_MiThermometer

[uer166]

For LoRa any MCU works, transceiver just a SPI device, just use whatever you already know well, it's a lot of work figuring out the datasheet and correct settings to be FCC compliant (at least in spirit), so you don't want any more unknowns. I used a STM32U5 series for very low power and large RAM for logs and framebuffer, but you don't need any of that for remote sensing, even an AVR Arduino would do.

[Finderbinder]

For LoRa any MCU works, transceiver just a SPI device, just use whatever you already know well, it's a lot of work figuring out the datasheet and correct settings to be FCC compliant (at least in spirit), so you don't want any more unknowns. I used a STM32U5 series for very low power and large RAM for logs and framebuffer, but you don't need any of that for remote sensing, even an AVR Arduino would do.

I mostly used Arduino (means Atmel mcu's). But as far as I know these mcu's are far from power efficiency. That is why I ask recommendations for power efficient platform.

[Buriedcode]

You can still use an Arduino sketch for lower power - it supports chips other than AVR, and even those have pretty good (not the best, compared to ulta low power MCUs) sleep functions.  Its the actual arduino boards that drive up the quiescent power - USB-UART bridge, regulators, power supply switching etc..

Using just the bare MCU - programmed with an Arduino compatible bootloader - and a header for a USB-UART cable means you just treat it as an Arduino. - just with the external USB/UART.

The downsides to using the Arduino core is that you're limited in MCU frequency choice, and it'll use up timer0 and I believe the UART periodically fires an interrupt to check for incoming data.
I'm pretty sure you can disable/override that so you can send the MCU to sleep without it immediately waking up to do background tasks. 

It's not quite the same as bare metal, but its a nice comprimise between the convenience and familiarity of Arduino, and the flexibility of bare metal.

[uer166]

For LoRa any MCU works, transceiver just a SPI device, just use whatever you already know well, it's a lot of work figuring out the datasheet and correct settings to be FCC compliant (at least in spirit), so you don't want any more unknowns. I used a STM32U5 series for very low power and large RAM for logs and framebuffer, but you don't need any of that for remote sensing, even an AVR Arduino would do.

I mostly used Arduino (means Atmel mcu's). But as far as I know these mcu's are far from power efficiency. That is why I ask recommendations for power efficient platform.

I see, in that case anything Cortex-M33 based on a good choice. My firmware consumes 2mA RMS running a whole bunch of graphics, UI, DMA to display at 10Hz refresh, and the LoRa/GPS stuff. If it's just a periodic sensor you'll be able to bring that down to maybe 10s or 100s of uA.

[fchk]

I need to monitor/collect temperature data (maybe other ambient data lately). Wires just do not fit. So I think battery powered LoRa is the way to go.
At first I hooked up on SX1262, but it is RF part only, so also mcu would be needed.

https://www.silabs.com/wireless/zigbee/efr32mg13-series-1-modules

This is a all-in-one solution, precertified. You can download the EU CE and RED certification documents. Saves you a ton on work.

It uses IEEE802.15.4 and Thread, and the main focus is on energy efficiency.

[Finderbinder]

I need to monitor/collect temperature data (maybe other ambient data lately). Wires just do not fit. So I think battery powered LoRa is the way to go.
At first I hooked up on SX1262, but it is RF part only, so also mcu would be needed.

https://www.silabs.com/wireless/zigbee/efr32mg13-series-1-modules

This is a all-in-one solution, precertified. You can download the EU CE and RED certification documents. Saves you a ton on work.

It uses IEEE802.15.4 and Thread, and the main focus is on energy efficiency.

LoRa is capable of much longer range compared to ZigBee (which in turn converts to better coverage and obstacle avoidance), if I think right.

[SiliconWizard]

LoRa is capable of much longer range compared to ZigBee (which in turn converts to better coverage and obstacle avoidance), if I think right.

Yes of course. It's also a much lower datarate. LoRa can cover many km with reasonable TX power. Pretty cool stuff, with some limitations of course in terms of datarate and (IIRC) allowed duty cycle.

[dobsonr741]

Two recommended parts:
RFM95CW 915MHz LoRa Module https://www.adafruit.com/product/5684
TPL5110 Low Power Timer https://www.adafruit.com/product/3435
Mix it with any MCU - not need to be low power

[Finderbinder]

Two recommended parts:
RFM95CW 915MHz LoRa Module https://www.adafruit.com/product/5684
TPL5110 Low Power Timer https://www.adafruit.com/product/3435
Mix it with any MCU - not need to be low power

Very handy module/IC, must have for many battery powered projects 
thanks