9 Replies Latest reply on Jan 3, 2015 5:03 PM by hk101

    Serial I/O on J3 not responding


      I have a minibreakout board. I was successfully using both the J3 and J16 USB to PC hook up so far.

      I used Edison+mini board with another USB device  (Freescale MK20DX256) hooked up to J3 (FT232R).

      Before the above hook up the FT232R on Edison was able to talk to PC, via PuTTY. However, after

      the interaction with MK20DX256 ( and disconnecting and re-connecting to PC), the FT232R no longer

      sends/receives any text on PuTTY. Edison shows :

      #stty -F /dev/ttyMFD2

      speed 115200 baud; line = 0;

      intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>;

      start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;

      -brkint -icrnl -imaxbel iutf8

      -isig -iexten -echo -echoe -echok -echoctl -echoke


      On PC, this J3 shows a virtual com port and PuTTY appears to connect to it (appropriate baud rate etc).


      Does the above behaviour mean the FT232R is busted?

      If not is there any utility to probe the FT232R from Edison side ( for example loop back?).


      I already looked up FTDI site for utilities to test this port and the FTDI utilities fail to see the installed FT232R (because of virtual port?).


      Do I need to replace the mini break out board? (Can I buy only mini break out boards anywhere?)

        • 1. Re: Serial I/O on J3 not responding

          Hello hk101,


          I'm not sure I got the idea, is your Edison not working?

          Or is the MK20DX256 not working?

          Or are they not communicating?

          Also why don't you check Intel Edison FAQ to see if any of the retailers there sell the breakout board separately?



          • 2. Re: Serial I/O on J3 not responding

            Hi Peter,

            Edison by itself is working, i.e. I can access Edison via WiFi terminal in Eclipse

            MK20DX256 board connected to PC via USB is working.

            Test was to see if Edison connected to MK20DX256  via USB could work.

            Before Test, Edison connected to PC via USB on J3 (FT232R) was working,

            After test Edison connected to PC via USB (J3) seems to be working on Edison side. I.e. if I check stty -F /dev/ttyMFD2 ,

            Edison reports serial (FT232 on J3) is working.

            Not working : PuTTY on PC connected to J3 via USB cable sees no chars

            (should be able to see Edison booting or root login prompt)

            OK will check the FAQ.

            Thank you

            • 3. Re: Serial I/O on J3 not responding


              Where is power coming from.  Normally with 2 USB cables, J16 is power and J3 is serial to putty.

              J16 is also the only otg port on the edison - microUSB A cable needed not microUSB Bcable.

              So if MX20DX256 is using J16, power needs to be either lipo on J2 or external 7v-15v on J21.


              Hope this was helpful.

              • 4. Re: Serial I/O on J3 not responding



                When I hook up Edison to PC, I use both J16 and J3 with two USB cables to PC. So, before the MX20DX256 tes,

                this two-usb-cable-to-PC was working just fine. After, the test ( test used J21 with power adapter to wall socket power),

                the same two-usb cable is showing abnormal behavior => Edison sees FT232R (ttyMFD2) working, PC sees COM port

                is working , PuTTY connects to (virtual) COM port, however no chars..


                I think there is some setup ( I checked different Baudrates, parities, bit combinations -- none work) issue inside the FT232R

                device itself.

                So one of my questions is : Is there a loop back test that I can run on Edison to check if FT232R is really Tx-Rx ing ?


                • 5. Re: Serial I/O on J3 not responding

                  hk101, I do not have a loopback test to offer at the moment, however, since J16 is otg it requires a special cable.

                  Either a microUSB A cable that complies to otg or a microUSB B cable with pins 1 & 2 shorted together. (from David Hunt)


                  J21 Power also requires the correct polarity when connecting - The specified item was not found.

                  I am pondering first the otg cable issue or possible incorrect polarity/current on J21 during the test.

                  • 6. Re: Serial I/O on J3 not responding



                    I used microusb B cable for MK20DX test. Did not make much difference.


                    I have used J21 with correct polarity even before my USB to USB test...so that is not the issue..


                    I think I have busted the USB side D+/D- transciever on the FT232R..some how.. but how to test?

                    • 7. Re: Serial I/O on J3 not responding

                      hk101, I am okay with the cable and power via J21.  I don't have a program to test a FT232R,

                      if it is possible to write this using c, gcc is installed on the Edison module.  I wish I had more to offer at the moment.

                      • 8. Re: Serial I/O on J3 not responding

                        Hi hk101


                        Any updates in this? Are you still having problems?




                        • 9. Re: Serial I/O on J3 not responding

                          Hi CMata,

                          No I was unable to fix the mini break out board. I think the transceivers are "suspected" broken.

                          I am unable to verify by any diagnostic tools.


                          I got around the issue by buying new mini break out boards from Mouser.