Due/Mega2560 multi Com-port adapter shield.

I am in the process of making a shield for a client that has a few serial ports with transceiver flexibility. I won't need too much SRAM for that one because the messages are small. I envision a more general solution that would be nice for maybe many people. One in which the ports of the CPU can take on different transceivers and have enough SRAM for buffers for a much more flexible shield. I would make it operable at either 3v or 5V in hopes of support for either DUE or MEGA2560. I want to use some Modules available on EBAY as plug ins to the Shield. for each port and I have Identified a set of them. Several flavors are interesting....RS232, RS485, and wireless NRF24L01 and ESP8266 come to mind... and maybe a single Ethernet port.....

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