Serial Interface 3.3V CMOS

Discussion in 'Embedded Systems and Microcontrollers' started by KansaiRobot, Jun 4, 2013.

  1. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    318
    5
    Hello Everybody.

    I would like to ask a question regarding serial ports on a board.
    I am reading the specs of one in particular and it says:

    CON2 Serial Interface RS232C
    CON3 Serial Interface 3.3V CMOS


    among others (USB, etc)

    Now I know that RS232 is the standard for serial ports but what do they mean by 3.3V CMOS?

    I ve never heard a type of serial port named like this. Anyone can enlighten me about this?

    Thousand thanks in advance:):)

    Kansai
     
  2. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Take a look at the RS232 voltage section here http://www.lammertbies.nl/comm/info/RS-232_specs.html The RS232 to logic voltage conversion is done by a RS232 level converter chip. A common chip is some variant of the MAX232 type chip. But then doing communication with other units. It can often be wanted to skip the voltage conversion part. And just connect to devices together if they use the same signal level (voltage) for IO. Your port 3 is made for such work. Remember that you may destroy this port, if you connect to a device with 5 volt IO voltage
     
    KansaiRobot likes this.
  3. KansaiRobot

    Thread Starter Active Member

    Jan 15, 2010
    318
    5
    Thanks for the reply.

    I remember vaguely that some years ago I used the serial port of a PIC and had to use a MAX232 to change voltages.
    So from what I understand of your post, my CON2 port would need this kind of conversion but the CON3 is adapted to a maximum of 3.3V. Is this correct?

    Thank you for all the help

    Kansai
     
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Yes the con2 is used for communication with devices that follow the RS232 standard. The con3 is for say direct serial communication between a 3.3 volt micro-controller and your board. Besides addressing the ports will behave exact same way seen from the software
     
Loading...