MSP430FR2355: Remove transistors in order to save space in my PCB and use the msp430fr2355 to work like a transistor.

Not nearly enough detail. But if the goal is to handle the input from some sort of encoder that has a quadrature output, then two input pins and some software usually does the trick for me.

Hi David,

Thank you for your response. Please be informed of our customer response below:

"This is my schematics:
https://prnt.sc/1et863n

I have a square signal connected to the gate of a transistor, which makes it open and close.
What i want to do is take out the transistor and directly connect the msp430 and make the msp430 to work like the transistor, always opening and closing.

What I'm doing now is changing a pin between output mode (like when we have a short in the transistor ) and input mode (high impedance). But it is not working very well, do you think there is another way to do this?"

I hope you can further help us. Thank you so much.

Kind regards,

Gerald

Still doesn't help as I have no clue what the original two transistor circuit was nor what the signal input and outputs are supposed to be.

Assuming that the I/O pin being switched between input and output modes has its PxOUT bit set to zero then it will behave more or less like the FET shown. Assuming that the input voltage is less than Vcc to keep the clamping diodes out of the picture and the channel resistance is low enough. The itty-bitty FETs inside a MSP430 are no match for a discrete FET when it comes to Rds(on).

I assume you have one pin as the "gate" and another pin as the "Drain". You can just use an input pin that supports an interrupt and have the ISR set a low output on the "Drain" when the "gate" goes high, and set a high output when the "gate" goes low. This method will have a time delay, however.