# JSON of mac\_payload misses f\_cnt in case of 0

**URL:** <https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934>\
**Category:** The Things Stack v3\
**Tags:** gateways\
**Created:** [September 26, 2023, 8:28pm UTC](https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934 "2023-09-26T20:28:16Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![pbttn2019](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/pbttn2019/32/44981_2.png) [@pbttn2019](https://www.thethingsnetwork.org/forum/u/pbttn2019)\
**Post date:** [September 26, 2023, 8:28pm UTC](https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934/1 "2023-09-26T20:28:17Z")

</div>

after changing the battery of an ABP device I found that the initial framecounter 0 is missing in the JSON structure:

frame 0:

```auto
data": {
    "@type": "type.googleapis.com/ttn.lorawan.v3.GatewayUplinkMessage",
    "message": {
       ...
        "mac_payload": {
          "f_hdr": {
            "dev_addr": "***",
            "f_ctrl": {}
          },
          "f_port": 1,
          "frm_payload": "***"
        }
      },

```

frame 1 and sucessors have the f\_cnt entry:

```auto
  "data": {
    "@type": "type.googleapis.com/ttn.lorawan.v3.GatewayUplinkMessage",
    "message": {
      ...
         "mac_payload": {
          "f_hdr": {
            "dev_addr": "26011480",
            "f_ctrl": {},
            "f_cnt": 1
          },
          "f_port": 1,
          "frm_payload": "***"
        }
      },

```

Is this a bug or an (un)documented feature?

---

<div class="post-metadata">

**Author:** ![kersing](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/kersing/32/44777_2.png) [@kersing](https://www.thethingsnetwork.org/forum/u/kersing)\
**Post date:** [September 26, 2023, 8:54pm UTC](https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934/2 "2023-09-26T20:54:33Z")

</div>

Have you tried forum search? This has been called out a couple of years ago already: [First f\_cnt is empty/null - world wide technical debt in progress](https://www.thethingsnetwork.org/forum/t/first-f-cnt-is-empty-null-world-wide-technical-debt-in-progress/45413)

---

<div class="post-metadata">

**Author:** ![pbttn2019](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/pbttn2019/32/44981_2.png) [@pbttn2019](https://www.thethingsnetwork.org/forum/u/pbttn2019)\
**Post date:** [September 26, 2023, 9:00pm UTC](https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934/3 "2023-09-26T21:00:56Z")

</div>

Did a search, but potentially used wrong keywords. Thank you for the hint!

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<div class="post-metadata">

**Author:** ![system](https://www.thethingsnetwork.org/forum/uploads/default/original/3X/6/2/6250ea44fd2b0d6259489e1a92748df681e1f970.png) [@system](https://www.thethingsnetwork.org/forum/u/system)\
**Post date:** [September 27, 2023, 9:01pm UTC](https://www.thethingsnetwork.org/forum/t/json-of-mac-payload-misses-f-cnt-in-case-of-0/64934/4 "2023-09-27T21:01:49Z")

</div>

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