# LHT65N datalog auto recovery issue

**URL:** <https://www.thethingsnetwork.org/forum/t/lht65n-datalog-auto-recovery-issue/73936>\
**Category:** End Devices (Nodes)\
**Tags:** dragino, end-devices\
**Created:** [July 12, 2026, 1:37pm UTC](https://www.thethingsnetwork.org/forum/t/lht65n-datalog-auto-recovery-issue/73936 "2026-07-12T13:37:36Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cooltag\_hw](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cooltag_hw/32/35697_2.png) [@cooltag\_hw](https://www.thethingsnetwork.org/forum/u/cooltag_hw)\
**Post date:** [July 12, 2026, 1:37pm UTC](https://www.thethingsnetwork.org/forum/t/lht65n-datalog-auto-recovery-issue/73936/1 "2026-07-12T13:37:36Z")

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**Summary**  
As stated in Dragino website user guide on LHT65N ([link](https://wiki.dragino.com/docs/LoRaWAN-End-Node/temperature-humidity-sensors/lht65n/#26-datalog-feature)), by enabling **SYNCMOD=1(Default)** and **PNACKMD=1, “_In a future uplink if LHT65N/S gets a ACK, LHT65N/S will consider there is a network connection and resend all NONE-ACK messages_** ”. So recovery of the samples during disconnection period happens automatically; but that’s not the case that I witnessed!

**I must also mention that I have deployed this feature on Dragino S31B-LB devices and it worked correctly as expected.**

**Logs**

As explained in the guide ([Section2.6.5](https://wiki.dragino.com/docs/LoRaWAN-End-Node/temperature-humidity-sensors/lht65n/#265-datalog-uplink-payload)), **Datalog Uplink payload** is as below:

 ![image](https://www.thethingsnetwork.org/forum/uploads/default/original/3X/b/3/b359817cbed00a742f02a8d7625affa8db22a755.png)

I realized that the issue is in bit no.6 of “Poll message flag & Ext” byte. Having **SYNCMOD** and **PNACKMD** enabled, I saw that after a period of disconnection the samples of that period are correctly sent in an uplink after reconnection and receiving the ACK. Below is an example of a datalog:

`“frm_payload”: "f/8J9wHSgWpTlQJ//wn5AdmBalOVD3//CfkB1oFqU5Ubf/8J+wHRgWpTlSd//wn7AdWBalOVM3//CfsBz4FqU5U/f/8J+QHSgWpTlUs=”`

payload converted from base64 to hex:

`7fff09f701d2816a5395027fff09f901d9816a53950f7fff09f901d6816a53951b7fff09fb01d1816a5395277fff09fb01d5816a5395337fff09fb01cf816a53953f7fff09f901d2816a53954b`

I take the first sample as an example: `7fff09f701d2816a539502`

and if we take the “Poll message flag & Ext” byte (in this example: `81`) and convert it to binary, we get: `1000 0001`

As you can see “Poll Message Flag” is `0`(!) while the format of the uplink is clearly a datalog one!  
This issue has caused the uplink payload decoder to fail recovering these samples.

I must repeat that the same feature works on **Dragino S31B-LB** with “Poll Message Flag” being `1` when it is recovering a datalog.

**Hardware**  
I am using an LHT65N with config below:

```auto
AT+ADR=0
AT+TXP=0
AT+DR=5
AT+DCS=0
AT+PNM=1
AT+RX2FQ=869525000
AT+RX2DR=3
AT+RX1DL=5000
AT+RX2DL=6000
AT+JN1DL=5000
AT+JN2DL=6000
AT+NJM=1
AT+NWKID=00 00 00 00
AT+FCU=12
AT+FCD=6
AT+CLASS=A
AT+NJS=1
AT+RECVB=0:
AT+RECV=
AT+VER=EU868 v1.3
AT+CFM=1,0,0
AT+SNR=0
AT+RSSI=0
AT+TDC=600000
AT+PORT=2
AT+PWORD=123456
AT+CHS=0
AT+SLEEP=0
AT+EXT=1
AT+BAT=2789
AT+WMOD=0
AT+ARTEMP=-40,125
AT+CITEMP=1
AT+RJTDC=20
AT+RPL=2
AT+TIMESTAMP=systime= 2026/7/12 13:33:54 (1783863234)

AT+LEAPSEC=18
AT+SYNCMOD=1
AT+SYNCTDC=1
AT+PID=0
AT+DDETECT=1,57600,59040
AT+SETMAXNBTRANS=1,0
AT+UUID=0A045C2F01322402
AT+PNACKMD=1
AT+EPLOGIC=0

```

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<div class="post-metadata">

**Author:** ![stevencellist](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/stevencellist/32/46434_2.png) [@stevencellist](https://www.thethingsnetwork.org/forum/u/stevencellist)\
**Post date:** [July 12, 2026, 2:41pm UTC](https://www.thethingsnetwork.org/forum/t/lht65n-datalog-auto-recovery-issue/73936/2 "2026-07-12T14:41:03Z")

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This sounds like an issue you should take up with Dragino!

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<div class="post-metadata">

**Author:** ![cooltag\_hw](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cooltag_hw/32/35697_2.png) [@cooltag\_hw](https://www.thethingsnetwork.org/forum/u/cooltag_hw)\
**Post date:** [July 14, 2026, 12:50pm UTC](https://www.thethingsnetwork.org/forum/t/lht65n-datalog-auto-recovery-issue/73936/3 "2026-07-14T12:50:47Z")

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Agreed

I needed to make sure I’m not missing out on anything