Do I understand correctly that m2web API allows me to access the data logged locally at the eWON? And the DataMailbox is a buffer in your cloud?
Yes, I think your understanding is correct and the DataMailbox essentially acts as a “buffer” for the data you are exporting.
is the bandwith stated on your website per eWON or per talk2m account?
The data bandwidth is per device and shouldn’t be an issue in most cases.
m2web API: does it make sure that there is no data loss when the internet connection is down?
The m2web API is just a programming tool to communicate with the ewon, it does not store data. I’m not sure I understand exactly what you’re asking.
whats the benefit of data mailbox?
The datamailbox is a central location where all of your data from various ewon devices can be extracted. It is a more direct connection and faster than having to download directly from the eWON.
DataMailbox data points: can a “rolling storage” be implemented that values are overwritten once it is full? Also, can it be expanded?
The datamailbox is essentially a buffer, like you mentioned, and data is automatically overwritten in a “first in first out” manner. It cannot be expanded or altered.
For more information, please see the DMWeb Programming page.