Getting datalog response of 00000000000

[Anna Black]

I'd really like to understand more about how the command to extract historical data from the data log works [command 31]. I've written some code to take my dates, convert them and format the package properly, and I know it works. Sometimes when I set a range of dates and send it to a device, the device will respond as expected with a return payload of groups of 11 bytes with data, but most of the time I get nothing. I am perhaps successful only about 25% of the time I send this request to devices.

I do spread it out so I don't go over airtime and fair-use restrictions, but at least half the times I make this request to a device I get no response at all.

When I do get a response, about half of those are a reply payload consisting of all zeroes (or all A's in Base64), and I'm picking time windows where I know the device has been logging. In my testing, I often pick a time window where I already have the data and I just want the device to send me that data so I can verify, but it's odd that I get either nothing or zeroes. 

I can believe that when I get no response at all, it is possibly because the device didn't receive the command, although I've done this with devices that are getting good signal and SF7, and they seem to receive other commands just fine. 

But when a device is responding with a data log of payload of all zeroes, what does that mean? Is that what I would expect if the device has nothing between those two timestamps, or are there other conditions that can cause the device to respond in that way?

Any help please.

AB

[Anna Black]

I can give a bit of an update to my own question as I've been running further tests for the last 24 hours.

If I use a 'confirmed downlink', then I can eventually get a response out of the device for every datalog request that I make. (I've always been advised to avoid confirmed-downlinks because of the overhead and airtime, but it was necessary for my experiment).

More than 50% of the responses I get are all zeros.

I have found if I repeat a known good date-range, then I do get a consistent positive result.

I'm now testing just small adjustments to the date-range to see which succeed and which fail.

I would really like to understand what's going on and how to get consistent, positive results from my queries of the datalog.