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Thread: T4 Hardware Serial Voltage Questions

  1. #1
    Junior Member
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    T4 Hardware Serial Voltage Questions

    I want to communicate with my Teensy 4.0 via serial from the com port of my computer. I looked at the T3.6 documentation and saw the use of a MAX232 chip to deal with +-12v to TTL level communication. I have a MAX232AEPE chip that I wired up but after looking at its datasheet, it lists 5v IO and the T4 says 3.3V only. Do I need to step the 5V I/O from the MAX232 chip down to 3.3v before sending data to the T4? If so, will I need to do it bidirectionally or will the MAX232 see the 3.3V as a high coming from the T4?

    Thanks in advance.

  2. #2
    Junior Member
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    Looks like i may need to switch to a MAX3232 instead of a MAX232. The MAX3232 is 3.3v I/O. Can someone confirm?

  3. #3
    Senior Member PaulStoffregen's Avatar
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    Yes, MAX3232 runs on 3V and has 3V I/O.

    You can also use the MAX232 with a pair of resistors to divide its 5V output signal down to 3.3V before going into Teensy 4.0's RX1 pin. The MAX232 has TTL level inputs. It recognizes anything over 2V as logic high and anything under 0.8V as low, so you can just connect Teensy's TX1 signal directly to the MAX232 input.

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