I’ve been searching for a way to send automatic downlink messages to my nodes with an NTP timestamp.
I’m not really sure how to integrate this as it seems you can only input things yourself in the messaging tab. Does anyone have any information on this?
What about the DeviceTimeReq, DeviceTimeAns MAC commands? They allow to get the current time from the network server by MAC command, so no dedicated implementation is needed.
Sorry, I’m not really grasping this concept. Do these MAC commands have to be put in code, or are they already transferred in the packet?
I know in the JSON file, there is a NTP signature. Is this already implemented then?
You really shouldn’t be sending downlinks very often.
When you do, it’s typically better that the node is the originating party making the request - which is how the device time request MAC command works.
What exactly is your actual application? Typically a cheap GPS receiver is a better way to get time.
I’m currently trying to monitor river levels. Would GPS give an accurate time reading?
Why wouldn’t you want to send downlinks often?
Just use the timestamps of the uplink packets then, which are applied by the network before the uplinks are reported to you. That way you also don’t waste battery capacity or airtime sending timestamps in the uplink radio packets, but simply use the ones in the metadata applied by the TTN servers.
If you research the subject at all you’ll find that it is the most precise source readily available to consumers / small projects - way better than NTP. GPS is a four-dimensional system, it can’t know where it is without knowing when it is, and given how huge a number the speed of light is, if has any sense of the where, it has an outsanding sense of the when.
Because it’s not allowed. Downlinks are very expensive of network capacity, strongly discouraged, and limited to a fairly low number.
Shaun,
Please invest some of you own time in researching the subjects you ask questions about. GPS is a well known source of accurate time stamps, a minute on google will tell you so.
And the problems regarding downlinks are listed all over the forum (apart downlinks from being limited by the fair access policy of TTN which I assume you are familiar with as user of the network?)
Is there a link to where you’re getting this information about down links? I can’t find much on why it isn’t specifically allowed.
As instructed look at the forum (use Forum Search Top Right of Page)… contributors get very frustrated when forumites ask repeated questions without demonstrating they have put in even the slightest effort to find information for themselves - information that is often repeatedly posted about or where a simple internet search will show gold!
I’m meaning official pages from The Things Network themselves, not forum pages. Even though this information might be helpful, its a question of how reliable this information really is.
Of course you need to question every little thing moderators and long time users provide. They have no experience and never answered these questions before…
However 10 seconds googling delivers:
https://www.thethingsnetwork.org/docs/lorawan/duty-cycle/#fair-use-policy
BTW. limiting downlinks to the absolute minimum and why that is a good idea is not something TTN mandates (they are quite liberal with 10 downlinks a day, commercial providers are a lot more restrictive), that’s hard earned experience by people that are actively using LoRaWAN for a number of years. There is no need to learn from other people experiences of course. You can make you own mistakes. Just make sure to minimize impact on other LoRaWAN users in your locality.
Please, for all our sakes and continued good will on our part, learn this. I don’t mean read it with half an eye on the football, I mean learn it. It is the bare minimum but it does get you a certificate.
https://www.thethingsnetwork.org/docs/lorawan/
When you join a community on a forum, you can read a selection of posts and see who’s saying what and who’s being corrected. On Discourse (this forum software) you can click on a name to see the users profile - which includes how much time they spend on the forum, how many 
's they have & have given, number of posts etc from which you can form an opinion. You’ve read just under 1,000 posts, myself & Jac have read ~35,000 and Jeff appears to have read them all.
Some of us are paid professionally to create IoT solutions which is what enables us to spend a bit of time on here. The cost for getting the advice on a one on one basis is infinitely higher but, with some warm & fuzzies, quite a few people get for free.
Hopefully this is food for thought.
PS, flood water monitoring is rarely split second timing, just use the uplink timestamp, no need for GPS or messing about with MAC commands.
I’ve actually read them all, just not all on the forum. E-mail notifications are an excellent way to stay on top of things…
'cause I’m still desperately trying to learn stuff…In my case will be honest and say ‘read’ =/= ‘understood’! What the heck I’m only here every day, even Xmas! 
