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  1. #1
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    Interfacing RN41 Bluetooth module to SoC

    I am trying to implement bluetooth connectivity for a power electronic module I am working on. For the control purposes, I have decided to use CY8C5868AXILP035 (Cypress SoC) 68-pin version on the board.

    Bluetooth module I am using is RN41 which works on 3.3V voltage level. Also, my SoC works on the same voltage level i.e. on 3.3V. I read in many documentations available online that bluetooth modules are generally connected with level shifters for making them compatible with microcontrollers of corresponding voltage levels. So is it not required to have level shifter for my application? I have never tried this before so any help would be appreciated.

    I am planning to connect RN41 to Cypress chip roughly schematized as follows:
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    So, basically can I directly connect RS232 to RN-41 if my chip operates at 3.3 V logic?

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  2. #2
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    Re: Interfacing RN41 Bluetooth module to SoC

    If both devices works at same voltage level no need to worry you can connect directly.

    If one is at 3.3v and another is at 5v and if it is UART interfacing (RX, TX) you can use simple resistor divider to connect the Tx of 5v chip to Rx of 3.3v chip. Connect directly the 3.3v Tx to Rx of 5v chip.
    (For CMOS high is >= 2/3Vdd to Vdd which means 5*2/3 = 3.333333 is fine)
    (For TTL high is > 2v and < 5v so this is also fine)
    So in both TTL and CMOS it satisfies the direct connection of Tx and Rx (from 3.3V to 5V)

    If it is RS232, the voltage levels are different, it is almost like +15 and -15 (depends on hardware also).
    So make it sure it is not RS232, else you need to use some MAX232 kind of chips to do the level conversion between TTL to RS232.
    All waveforms, no matter what you scribble or observe in the universe, are actually just the sum of simple sinusoids of different frequencies....

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