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Observer
Observer
866 Views
Registered: ‎07-30-2018

Internal UART 16550 RS485 bus

I'm curious if there is any issue with building an internal RS485 segment in PL.

External connection to an RS485 bus would be made through a single interface, while I could have multiple internal interfaces using UART 16550 modules. 

I'm assuming I could do this by connecting the RX/TX and RS/CTS with appropriate logic to distribute internally and propagate the OR of all signals to external.

 

I don't see any technical reason this would fail in either the RS485 or logic sides, does anyone else?

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Adventurer
Adventurer
818 Views
Registered: ‎05-23-2018

RS485 usually has a pretty bad Common Mode voltage that might destroy your FPGA. Additionally, the signal levels of about 5V would also damage any FPGA I know.

 

I would recommend using an external RS485 transceiver and use a standard UART internally. 

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Observer
Observer
808 Views
Registered: ‎07-30-2018

I intend to have an external transceiver, but I want to have multiple PL UARTs sharing the same external transceiver. 

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