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PSoC 4 MCU

DaEr_349131
Contributor

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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1 Solution
JoMe_264151
Expert II

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
JoMe_264151
Expert II

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

View solution in original post

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DaEr_349131
Contributor

true, thanks!

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

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JoMe_264151
Expert II

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

Bob

DaEr_349131
Contributor

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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