Mention .../ack is only for protocol v2.

brocaar · web-flow · commit 28ec9911199d · 2017-12-15T14:51:46.000+01:00
diff --git a/docs/content/use/data.md b/docs/content/use/data.md
@@ -118,6 +118,9 @@ Topic for received TX acknowledgements (or TX errors). Example payload:
 }
 ```
 
+**Note:** this topic is only available for gateways implementing v2 of
+the packet-forwarder [PROTOCOL.txt](https://github.com/Lora-net/packet_forwarder/blob/master/PROTOCOL.TXT).
+
 Possible error values are:
 
 * `TOO_LATE`: Rejected because it was already too late to program this packet for downlink

Original file line number	Diff line number	Diff line change
`@@ -118,6 +118,9 @@ Topic for received TX acknowledgements (or TX errors). Example payload:`
`118`	`118`	`}`
`119`	`119`	```
`120`	`120`
	`121`	`+Note: this topic is only available for gateways implementing v2 of`
	`122`	`+the packet-forwarder [PROTOCOL.txt](https://github.com/Lora-net/packet_forwarder/blob/master/PROTOCOL.TXT).`
	`123`	`+`
`121`	`124`	`Possible error values are:`
`122`	`125`
`123`	`126`	* `TOO_LATE`: Rejected because it was already too late to program this packet for downlink