Hello,
Regarding MQTT Last will and testament currently consulting with RnD. Moving to your other question which is: how often readings are uploaded, when using MQTT on our devices, router does not send data, you as user need to "ask" router to provide certain data, so when you "ask" router certain data you get the data from that point, so we can say the data is always updated.
Regarding MQTT on our devices, it is for devices monitoring, and you can get these parameters which are mentioned here: https://wiki.teltonika-networks.com/view/Monitoring_via_MQTT
If you want to get more information via MQTT from the router, then what you can try and to is:
1. Enable device to work as Modbus TCP Slave;
2. Configure Modbus TCP Master, so that router would collect certain data from itself: https://wiki.teltonika-networks.com/view/Monitoring_via_Modbus;
3. Configure MQTT Gateway, and from other side of MQTT you can send request to router via MQTT to get routers data via Modbus
To get Modbus data from Modbus TCP slave by using MQTT you need to use following messages, example for getting devices uptime:
- 0 65432 0 192.168.1.247 560 5 2 3 2 2
0 - it should be by default always
65432 - it should be by default always
0 - 0 means IPv4, 1 means IPv6, 2 means hostname
192.168.1.247 - IP address of Modbus TCP Slave
560 - Port number on which Modbus TCP slave is listening
5 - timeout
2 - slave ID
3 - Modbus function (3 - read holding registers, 6 - write to a single holding register, 16 - write to multiple holding registers)
2 - Register number/address
2 - Number of Registers
