AudioMoth app installed on Amazon Fire HD 8 Plus (10th gen).
AudioMoths 1.0.0 & 1.1.0 (two of each)
Firmware versions 1.5.0, 1.6.0 & 1.8.0 (same behaviour in every case)
In each case, with AudioMoth in Custom mode and time not set: Red LED constant & Green LED flashing once per second as expected. When chime is played Green LED momentarily flashes rapidly then returns to slow flashing with constant Red LED. Thus the devices are detecting the tone sequence but not recognizing the instruction to set the time.
The tablet is playing an audible chime with the phrase C5:1 D5:1 E5:1 C5:3 and analysis of the chime confirms the presence of an 18kHz tone encoded in 5, 7.5 and 10ms bursts. This indicates that the tablet is correctly playing a tone sequence but whilst the devices are responding to the tones the clocks are not being set. I have experimented with varying both the volume of the tablet sound output and also the distance between the tablet speaker and the AudioMoth microphones with no effect.
The time can be set using the PC Time app, whereupon the devices behave correctly when set to Custom mode.
EDIT: I've also tried programming the AudioMoths to use both UTC and local time - no difference
Unfortunately my Android 'phone is too old to run the AudioMoth app and I only have 32 bit laptops running XP so I can only use the tablet to set the time when in the field.
@Alex Rogers Thanks for your replies. It appears that the problem is with the AudioMoth app downloaded from Google Play. Your alternative firmware makes no difference - the app will still not set the time. However the chime from the webpage works perfectly when played from the internal speaker of the same tablet at about the same volume as the app (works even with firmware 1.6.0). Not a viable solution in the field though as it will depend on finding a wi-fi hotspot!
The tablet doesn't have cellphone capability and my phone is too old to play the tones from the webpage (I can open the page but the tones won't play).
Try the firmware version below which should be a bit more flexible to varying volume levels. https://www.dropbox.com/s/vmya2cdeygiyja8/AudioMoth_1_8_1_RC2.bin?dl=0
Tablets sometimes don't reproduce the high frequencies as well as their speakers are often larger than smartphone speakers. Touching the tablet against the PCB close to the microphone also helps sometimes.