MCU programming using MAX232

Discussion in 'Homework Help' started by prakhars, May 30, 2012.

  1. prakhars

    Thread Starter New Member

    Oct 4, 2011
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    Is it necessary to use MAX 232 IC for AVR Microcontroller programming.????

    Because i have seen many programmer circuits that on programming with RS 232 protocol uses MAX 232 and there are also many that without using any intermediate IC, programs the circuit simply by connecting some resistors and transistors in between the serial port and the MCU.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    The MAX232 or any RS-232 to TTL converter chips are not absolutely necessary.

    The output from a PC COM port is typically about +/- 10V but can be anything from +/- 5V to +/- 15V.

    The purpose of the MAX232 is to convert those +/- voltages to TTL levels, usually 0 to 5V, in both directions (receiver and transmitter).

    You can accomplish the same thing using resistors and transistors.
     
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  3. prakhars

    Thread Starter New Member

    Oct 4, 2011
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    So it doesn't mean that the use of MAX232 is must.
    We can use RS232 port directly for any of Microcontroller,.......
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,442
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    If you wish to connect one MCU to another MCU you do not have to use RS-232.
    You can connect the SCI TTL signals directly.
     
  5. mlog

    Member

    Feb 11, 2012
    276
    36
    You should avoid connecting RS232 directly to TTL because the higher RS232 voltages can damage the TTL device.
     
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