How to read GPS data (RS232) by BeagleBone (3.3V TTL)

Discussion in 'General Electronics Chat' started by rkrasowski, Aug 25, 2012.

  1. rkrasowski

    Thread Starter New Member

    Jul 10, 2012
    I am trying to read GPS data via BeagleBone. GPS is giving me RS232 ( +/- 12V), I can read this with no problem with serial port on PC. I understand that BeagleBOne accept only 3,3V, so I used MAX232EIN to lower RS232 to TTL level. After that I can not read output using my serial port on PC. I get some gibberish. Looking at the oscilloscope I see output after MAX232 of 0-5V, inverted as compare to original signal and good quality. What is missing??
    Can serial port read TTL signal?
    My plans is also to use Logic Level Converter BOB-08745 by Sparkfun to get to 3.3 V level as needed by BeagleBOne.

    Is my thinking correct, and why I can not read serial data after using MAX232 and converting RS232 to TTL?

    I also did experiment by converting TTL signal back to RS232 using another channel of MAX232 and again signal became readable.

    Thanks in advance