I´m working in a tiny webserver. This webserver should be able to report data from a boiler. This boiler has RS485 (modbus rtu 8n1) communication, and I have the whole table. I´m getting into Modbus for first time...
a) All these libraries are intended for using rx and tx channel (0-1 pins), so, probably, adding a ethernet and willing to use both ethernet and SD card would mess things a lot. That´s why I´ll use a mega 2560. All you know why. Nevertheless, I don´t know how to change those settings in order to select other rxtx channell from mega board.
b) How can I get from boiler just the lines I need at once but not all?
Could you send me some "must read" links to go straight into it?
Any other suggestion?
a) All these libraries are intended for using rx and tx channel (0-1 pins), so, probably, adding a ethernet and willing to use both ethernet and SD card would mess things a lot. That´s why I´ll use a mega 2560. All you know why. Nevertheless, I don´t know how to change those settings in order to select other rxtx channell from mega board.
The Ethernet Shield does not use the UART on pin 0 and 1, so no, I don't know why you use the Mega2560. Also using Ethernet and SD cards together is no problem if you keep in mind that they both use the SPI bus and you have to ensure the chip selects are properly signaled (although the libraries usually take care of that).
b) How can I get from boiler just the lines I need at once but not all?
Ask the manufacture or post a link to the boiler's datasheet.
If you want to use a different Serial object you will have to rename all the "Serial" instances to "Serial1" or "Serial2" depending on which port you want to use. If you need any help on connecting and communicating with the boiler slave please provide details of the register out lay (address table).
