So I did 2 more experiments:
- frequency plan set to RX2/SF12, placed at old location (few meters + brick wall) and triggered an OTAA join → result: no measurements are received after the initial data messages; blue led blinks 7 times (short), followed by 2 double blinks (i.e. after inserting the battery)
- frequency plan set to RX2/SF9, placed at second location (also few meters + a brick wall) and triggered another OTAA join → result: measurements are received every 5 minutes; blue led
blinks 7 times (short) followed by 3 double blinks (i.e. after inserting the battery)
That means that the frequency plan variant doesn’t make a difference, but the initial location of the OTAA join is crucial. After the join is completed, the location doesn’t matter anymore.
PS: FWIW, Browan hasn’t processed my account request for days. Thus, I can’t access the TBHV110 reference manual on their site. However, I found a copy at https://docs.microshare.io/assets/pdf/TBHV110.pdf It contains some details, but isn’t comprehensive. Especially, it doesn’t describe the LED blink codes, at all.
PPS: After removing the battery the last time I shorted the +/- contacts using a small resistor in order to empty any built-in capacitor. Before inserting the battery again I measured the voltage as 2.65 V (instead of the previous 3.6 V). The drop was sufficient for the OTAA join to be initiated. Previously, I just let the device sit for a few hours without the battery inserted. Again, the reference manual doesn’t mention anything about how the device is supposed to be reset, how the OTAA join can be initiated, etc.