Do you know if its CE/ETSI cert?
probably not Jeff 
Theoretically I can use/lend a big chunk of the LoRaWAN_TTN_Env_Node code from @lex_ph2lb and lowpower from @Charles 
I’m thinking of an indoor double function node, PIR alarm and/or TempHum
no turning back now 
hardware almost done
I will use this lv power switch from Pololu as a test.
One push is on and another is off… but, you can do that under software control too, remote completely switch off the power of the node hence alarm
- Pololu - Mini Pushbutton Power Switch with Reverse Voltage Protection, LV
- Mini Pushbutton Power Switch with Reverse Voltage Protection, LV Pololu 2808 - vanallesenmeer
- Mini Illuminated Momentary Pushbutton - Blue Power Symbol : ID 3105 : Adafruit Industries, Unique & fun DIY electronics and kits (small button-blue led)
- update : found the switches in an NL based online shop and they have a lot more nice parts
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Respect !!!
Wich techno, Mesh BT? Definitively not LoRa compliance 
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In the space shuttle they used 3 systems (2 for backup) but you need 4?
But the switch is still a single point of failure. 
Did you already check how accurate these PCF8563 RTC’s are ?
The 32768Hz Xtals used on those RTC boards are sometimes really bad. (Ofcourse depending on the manufacturer of the modules). I’ve had RTC modules that were off time more than 10 seconds/day and could not be corrected.
Now I only use the DS3231 with it’s oscillator inside the chip with can be finetuned +/- 10ppm in steps of 0.1ppm. Stability of a DS3231 can be as good as +/- 1 second/month.
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yes I know… its only for the /poc / picture
I have some 3231 modules and I ordered some 3231’s to make my own ’ I2C multiple timerboard.
maybe I can use one external x oscillator for multiple RTC’s ?
I think you can, usually the on-chip oscillator circuit has an output (pin) and an input (pin), leave the output open and inject capacitive an external timing signal on the input pin.
and I have to write / extend an RTC lib to set and sync them before use (and later once a month/year ?)
I’m not sure what the application is, but syncing with NTP (e.g. with an ESP-01) is not possible?
yes that’s possible… but only on the workbench, later in ‘the field’ I must find another way to sync them (remote)
If in the field, couldn’t you sync by GPS?.
Power a ublox module up for a minute once a week or so to save battery.
That’s even more fancy, time synchronisation via multiple satellites. 
That is even a better plan, sync your in the field RTC with LoRa. 
what would be the (data) flow of an RTC node sync over LoRaWAN ? 
I do not know. Maybe send a short dummy packet at exactly the whole hour so your node can sync minutes/seconds on that ?
No that can’t work… there’s always a delay, so first determ the network delay and then correct the time before flashing the RTC ? we can always ask Olga from 'Deutsche Bahn
I don’t know how they do it at DB but that should be really easy. Uplink packets get the timestamp from TTN/Gateway - then just add the current timestamp from the clock for the tx-packet. That is enough to calculate the clock-offset and then if needed send a correction value via a downlink packet.
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