right this way. to suggest this circuit MAX3322, now the problem is that is not what is normally a PCI card as normal output of a PC, unless you do a power booster and repeater right through this and from there you depart for your communication , is also an option
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then. if you were to use 232, with 16 devices can suppose that distance between each? and as an RS232 network to behave interference present?
If we place a booster as suggested MAX3322, because the current PCI cards or current PC does not have the ability to withstand such a load current,
why not make a direct USB converter> 485 taking the energy from the USB port itself. And place a device 485 for each micro terminal having the option and advantage so you know that the potential for interference WILL maintained by the kind of communication gap 485 and the distances and speeds will more easily be managed