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MSP430F5438A: IO configuration of MSP430f5438A

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Replies: 4

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Part Number: MSP430F5438A

Hi team,

Can we configure MSP430F5438A GPIOs as Open Drain when it is configured as Output?

In our design we are using one of the MSP430F5438A GPIO as a control signal to an I2C Buffer whose IO level is 1.8V, which is conflict since MSP430 IO level is 3.3V. So if we can configure that GPIO as Open Drain then this will work since we given pull-up externally to 1.8V.

  • Hi Chandrashekhar,

    I believe this thread describes how to setup an MSP430 GPIO for OC operation:

    https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/330994?MSP430F5510-GPIO-type

    BR,
    Leo

  • In reply to Leonardo Estevez:

    Hi Leo,

    Thanks for the Reply..!!

    The thread you shared resolves the issue when the GPIO is configured as Input, but when it is configured as Output the answer suggested in the thread is little confusing.

    My query is when the particular GPIO is configured as Output, whether it can be configured as Open Drain? 

  • In reply to Chandrashekhar D R1:

    Hi Chandrashekhar,

    One can emulate an open drain behavior by setting the output register of a GPIO to low, and switch it by using the direction register between input and output. If set to output it will actively pull the signal low and open the current path to GND, like an active open drain, while in input direction it will be high impedance pulled up by the external signal, like an inactive open drain.

    The important limitation in comparison with a true open drain is the pulling signal level does not have to exceed the MSP430 supply voltage level, as then the clamping diodes would short the signal, while a true open drain can take higher signals then the supply voltage.

    BR,

    Leo

  • In reply to Leonardo Estevez:

    Hi Leo,

    Thanks a lot for the detailed description and it helped a lot. 

    Thank you..!!

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