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PSoC™ 4 Forum Discussions

DaEr_349131
Level 5
5 comments on KBA First comment on KBA 100 replies posted
Level 5

Hi,

When using UART (scb mode), the most use case is that one would use the built-in pull-up on the TX-line (not adding an external pull-resistor).

Questions:

- What is the pin/drive type for the UART TX pin?

- Can this be changed?

- Use case is to connect two UART's in parallel (software knows when it's ok to send).

  Would it be safe to just tie them together or should I wire the TX coming from "CPU 2" to an input of "CPU 1" to achieve a buffer, and also the option of adding a simple logic block that checks if uart_tx on "CPU 1" is driving, thus disabling incoming TX, not passing it through.

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Bob_Marlowe
Level 10
First like given 50 questions asked 10 questions asked
Level 10

You may set the UART to show its terminals and connect IO pins to them. With Pin_SetDriveMode() you can set the pins to digital High-Z when needed and back to strong mode to transmit data.

Happy coding

Bob

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4 Replies
Bob_Marlowe
Level 10
First like given 50 questions asked 10 questions asked
Level 10

You may set the UART to show its terminals and connect IO pins to them. With Pin_SetDriveMode() you can set the pins to digital High-Z when needed and back to strong mode to transmit data.

Happy coding

Bob

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DaEr_349131
Level 5
5 comments on KBA First comment on KBA 100 replies posted
Level 5

true, thanks!

in other words, default uart is strong drive high & low (not open drain) right!?

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Bob_Marlowe
Level 10
First like given 50 questions asked 10 questions asked
Level 10

It is your choice. Strong drive will work without any extern components and is the usual choice.

Bob

DaEr_349131
Level 5
5 comments on KBA First comment on KBA 100 replies posted
Level 5

I have two cpu's on the same uart, even though the protocol takes care of the two not talking at the same time, it's a risk if one drives low and the other high...

Let's say I reconfigure both as open-drain + external ~10k pull-up.

What would be a reasonable max speed ?

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