about rs-485 implementation

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1. Can I use UART peripheral that is provided in SOPC builder to implement RS-485 communication (or is the available UART only for RS-232)? If I can't use it, do you have any suggestion how to implement RS-485 in SOPC?

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The answer is yes.

RS-485 and RS-232 refer to the physical layer, i.e. the signaling levels.

Both can use UART or whatever else.

The main difference is:

RS232: +/- voltage, single ended. Full duplex (one wire for tx and one wire for rx)

RS485: differential signaling (line driver/receiver). Half duplex (same line shared for rx and tx)

There is a third one:

RS422: differential signaling (line driver/receiver). Full duplex (separate lines for rx and tx, total 4 wires)

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2. So if I can use the available UART to implement RS-485, it means I can also use the UART HAL driver for my RS-485, doesn't it?

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Sure, but you need to manage the half duplex operation. Usually you have an extra output pin which switches the RS485 transceiver between tx or rx mode.

If you use RS422 you don't need to change anything.

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3. About the hardware implementation, I'm planning to implement RS-485 by assigning UART Tx and Rx to two pins in HSMC connector, is it possible? Are there any things that I have to consider about this implementation, like voltage signal level, buffer requirement etc?

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Both RS232 and RS485 require an external driver.