I’m sorry if this is a dumb question but I’m trying to make sure I’m understanding correctly. We are trying to send/receive Modbus commands from a PC to a remote pressure sensor connected via RS485. The PC will send a modbus command to retrieve pressure/temperature and the remote sensor will respond with the data requested. Is this possible? In order to achieve this, do I need two Arduino boards and two XBee boards? One for the PC and one for the remote pressure sensor?
That is entirely dependent upon the sensor and software on the PC on what you need. If you have a software program that is already designed to send Modbus commands, than on the PC side all you need is the XBee module mounted on an RS232 or USB interface board.
On the Sensor side, if you get a sensor that understands Modbus, then it would be the same.
You only need to go the Arduino rout on the sensor side if the sensor does not speak Modbus.
Thanks for the response. So on the PC side I can get the XBee S2 and on the sensor side I can just get the XBee RS-485 adapter? If so, is this the one you’re referring to? http://www.digi.com/wiki/developer/index.php/XBee_RS-485_Adapter
I would just go with a 900 HP modem on each side.
That is providing your sensor has an RS485 output and communicates over Modbus.
I like the idea of the 900 HP modem but I was hoping to do without an external power supply and keep costs down. It does have RS485 output and communicates over Modbus. This kit also looks promising: http://www.digi.com/products/xbee-rf-solutions/modems/xbeeadapters
Any other ideas?