[HDMI2USB] Create a serial port extension board - Support both RS232 and RS485 modes. about getting-started HOT 4 OPEN

This can be achieved using SP331 transcevier.
The SP331 is a programmable RS-232 and/or RS-485 transceiver IC. The SP331 contains four drivers and four receivers when selected in RS-232 mode; and two drivers and two receivers when selected in RS-485 mode. The SP331 also contains a dual mode which has two RS-232 drivers/receivers plus one differential RS-485 driver/receiver.
The RS-232 transceivers can typically operate at 230kbps while adhering to the RS-232 specifications. The RS-485 transceivers can operate up to 10Mbps while adhering to the RS-485 specifications. The SP331 includes a self-test loopback mode where the driver outputs are internally configured to the receiver inputs. This allows for easy diagnostic serial port testing without using an external loopback plug. The RS-232 and RS-485 drivers can be disabled (High-Z output) by controlling a set of four select pins.

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A lot of care should be taken in figuring out the correct connectors for
http://www.zytrax.com/tech/layer_1/cables/tech_rs232.htm

RS-485/RS422 should probably end up on RJ45 style connectors.
RS232 should end up on good old DB9 connectors.

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Two Linux Kernel Drivers which support multiple serial ports on a single endpoint are;

• edgeport
• mxuport

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Example designs from previous student;

from getting-started.