send an receive data from modem
Assuming some sort of energy metering project.
What modem specifically are you using? Can you provide links to description or documentation?
Would imagine USART, SPI or I2C would be normative modes of connectivity.
"euridis modem " for remote communication between an energy meter and a concentrator (stm32 ...)
A modem - any modem - is simply device which connects a "host" (or "DTE") to some communications link.
Modem - Wikipedia
Details of how the modem interacts with its "host" will be in the modem's documentation.
So: have you studied this modem's documentation?
As Clive One said, UART/USART, SPI, I2C would be common ways for a modem to interact with its "host". Again, this will be detailed in the modem's documentation.
A common protocol for a modem to interact with its "host" over UART/USART is to use so-called AT Commands:
Hayes command set - Wikipedia
And, again, this will be detailed in the modem's documentation.
euridis modem is going to be realized by me and I find difficulty in the design part of this modem that will realize the communication between energy meter and PC
So are you familiar with the basics of how any modem interacts with its "host" ?
Surely, that would be the place to start ...
Are we talking about this: Euridis association ?
And, thus, about this: IEC 62056 - Wikipedia ?
But, presumably, not this: https://www.euridis-ecole.com/ ?
Retrieving data ...