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I've been observing some undocumented behavior of the MODBUS Data to Server.
If the unit doesn't have internet access it stores the mqtt messages and sends them when the network is reestablished.

This is really a usefull feature but I could use some clarification:
1. What is the max size? How many messages?
2. Are there any rules in place for this? I.e. what data is dropped when it gets full? FIFO?
3. I've seen that it usally drops the first 2 min of data before it starts storing them. What triggers the TRB145 to start "saving to local storage"?


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Thanks for contacting TELTONIKA | Crowd-support forum.

When Modbus slave device return answer to Modbus master, the master stores the data inside RAM memory, master constantly reading the data and constantly storing the data inside router temporary memory depending to the Interval at which requests are sent to the slave device.

The maximum size of database is 20 000 registers, if the database reaches its capacity, the first register will be erased to allow the new register stored and so on. If the router goes down, the router loses all data cause data are stored inside RAM memory.

A Modbus request is a way of obtaining data from Modbus slaves. The master sends a request to a slave specifying the function code to be performed. The slave then sends the requested data back to the Modbus master. You can create a maximum of 64 request configurations for each slave device.

The Data to Server service provides us with the possibility to set up data senders that collect data and periodically send it to remote servers via HTTP(S) | MQTT | Kinesis.

The period for data to server does no mean how often the TRB145 will send data to a remote server, but how often the TRB145 will check the database for newest unsend data.

If there’s newest unsend data in database, then TRB145 will send it to a remote server.

If there’ s no newest unsend data in database, then TRB145 will not send any data to a remote server.

Modbus and Data to Server are two services working separately.

More information can be found here:



Best regards,