You need a RS232 TO RS485 BOX that is, the converter, this thing is very small, like a matchbox, the price of 5 yuan yuan ~ 30,000 euros ranging from the general government departments can buy 30,000, the rebate is 28,000 or so. If it is a small unit, get a 30 fast money on it.
The 485 must not be wrong, or it will not work.