I want to read the soil moisture data from CS650 by using Arduino Mega 2560 board. CS650 output format is SDI-12 as well as Serial RS232.
Can i connect CS650's Green(Tx)/Orange(Rx) wires directly with Mega's RX0/TX0 or shall i use the Max3232 module between arduino and CS650?
if someone has tried this earlier, please share the wiring diagram/example source code.
Warning: Take what I'm about to say with a rock(not a grain) of salt. I've only just started at CSI recently and I don't know a lot about this specific peripheral... Or electrical engineering, for that matter.
The Arduino Mega 2560 works at 5v TTL, I believe. You won't be able to use it alone to speak with an RS232 device. However, as long as you have a power supply that's 12v hooked directly to the sensor and a common ground between the sensor and the Arduino, you may be able to use SDI-12 as SDI-12 logic levels are very similar to 5v TTL. A separate power supply for the CS650 would probably be necessary anyways because the Arduino Mega 2560 can only supply 40mA over its pins.
If you're interested in doing this, maybe take a look at this open source project to support SDI-12 on Arduinos without any additional hardware: https://github.com/EnviroDIY/Arduino-SDI-12