10 Replies Latest reply on May 17, 2014 5:06 AM by noalac

    Intel Galileo serial port(audio jack) lags?

    noalac

      Hi,

      I just got the Intel Galileo board and wanted to try the serial port(audio jack). I have the special 3.5mm to serial cable, and connect the board to my laptop(using another serial to usb cable together).

       

      The problem is:

      when I open a putty and start the serial session, I find it extremely lag to communicate with the board. I have to quickly press Enter several times, only to see one new line shows up. It is impossible to input some commands like ls or cat and see the result.

       

      More information:

      1. I notice that the input to board(which connects the PIN2 RING RXD of galileo board) works correctly. When I input root to login, even if I can't see what I input(because of the strange lag problem), after several Enter, I can find myself do logged into the system as root. So the problem may lie in the output part.

      2. I use a multimeter to test the PIN3 TIP TXD to ground. And find that PIN3 TIP TXD is actually shorted to ground at the beginning. After one or two seconds, the resistance between PIN3 TIP TXD and ground remains stable at 4.66K ohm. However, the PIN2 RING RXD is always open to ground.

       

      That is all I know for now. This problem happens on my two Intel Galileo boards, so it may be a common problem.

      I doubt if there is some "bug" in the manufacture or board design? Anyone else has the same problem?

      I'd appreciate any advises or suggestions.

       

      Thank you!

        • 1. Re: Intel Galileo serial port(audio jack) lags?
          shadowrecon

          i experienced the same very problem today, could not locate the exact problem so just went back to using ssh over wifi with no problems,

          • 2. Re: Intel Galileo serial port(audio jack) lags?
            noalac

            Yes.

            I can connect the board normally with ssh/telnet(use Ethernet cable) or arduino IDE(use the USB Client port).

            This problem only happens at the audio jack serial port.

            • 3. Re: Intel Galileo serial port(audio jack) lags?
              rmm200

              I can only tell you on a correctly wired cable and a functioning Galileo, there are no dropped bits or lag.

              My serial connection is extremely reliable, fast, and is my fallback when nothing else is working.

               

              You don't specify what rs232 to usb converter you use. Mine is by Manhattan and works well:

              Amazon.com: Manhattan USB to Serial Converter Connects One Serial Device to A USB Port (205146): Computers & Accessories

               

              I would also review flow control protocols and see if yours are set correctly:

              Flow control (data) - Wikipedia, the free encyclopedia

               

              And last - check the wiring on your cable. Make sure ground is good - and not touching anything else.

              If your cable does not have a logic chip in it for serial conversion - it is the wrong cable.

              1 of 1 people found this helpful
              • 4. Re: Intel Galileo serial port(audio jack) lags?
                noalac

                I think the problem is not in the cable.

                Though I am not using the same cable with you, I can tell you how I check the cable and board:

                1. Cable check:

                Connect 3.5mm to rs232, and rs232 to usb, and usb to my laptop. Now I can see a COM device appears on my laptop. (I don't connect the board right now because we just want to check the cable). Next, I use a small wire to short the RING and TIP of 3.5mm audio port. We know the RING and TIP are connecting the RX and TX of serial port, so we actually connect the RX and TX(the 2 and 3 pin of serial port), and what we input will instantly appear on the putty session.

                The result is exactly what we expected. The input is exactly the output, no lag, no error, very reliable. It means that the 3.5mm to serial cable, the serial to usb cable and the usb cable driver are all working correctly.

                2. Galileo board function check:

                I boot with both the image in SPI flash and full Linux image in SD card. (SD card image are downloaded directly from Intel website). Both can work correctly, and I can upload sketch through USB client port. I can also connect the board with ssh and telnet, with no lag. The only thing that not works correctly is the audio jack serial port.

                 

                Since your board's audio jack is good. Could you use a multimeter and measure the resistance between the TIP TXD and SLEEVE gound on your board?

                I want to know if the TIP TXD is open to SLEEVE gound on your board, thank you!

                • 5. Re: Intel Galileo serial port(audio jack) lags?
                  AlexT_Intel

                  I don't have any lag either with my custom-made 3.5mm to RS-232 + cheap noname RS-232 to USB cable, so at the end of the day it may be your cable or a combination of your cable(s) and Galileo. I don't have Galileo with me right now to measure what you've asked for, sorry.

                  • 6. Re: Intel Galileo serial port(audio jack) lags?
                    grapaZ

                    "I use a multimeter to test the PIN3 TIP TXD to ground. And find that PIN3 TIP TXD is actually shorted to ground at the beginning. After one or two seconds, the resistance between PIN3 TIP TXD and ground remains stable at 4.66K ohm. However, the PIN2 RING RXD is always open to ground."


                    noalac, I see something similar with my homebuilt cable that works just fine.

                    I get TIP open to ground. And 4.7 K ohm between RING and SLEEVE.


                    I have no idea what that means.

                    But perhaps you have TX and RX swapped. ( that would still pass your cable check. )


                    regards,

                    jl.z



                    1 of 1 people found this helpful
                    • 7. Re: Intel Galileo serial port(audio jack) lags?
                      noalac

                      Thanks Alex,

                      It seems that I need to test other cables and see the result.

                      • 8. Re: Intel Galileo serial port(audio jack) lags?
                        noalac

                        I have bought a new 3.5mm to uart serial cable. Unfortunately the cable doesn't work normally as well.

                        To grapaZ , I tried to swap the TX and RX, and the result is I got nothing from the putty at all. So my connection of RX and TX is correct.

                        It seems that the problem is on the board. I will have to talk with Intel if possible.

                        Thanks guys for your help!

                        • 9. Re: Intel Galileo serial port(audio jack) lags?
                          SpiderKenny

                          Instead of measuring OHMs you could try measuring Voltage.

                          The TX line should measure somewhere between -6 and -12 V when not transmitting any bytes, as this is he RS232 level for a logic '1', and should measure between +6 to +12V when transmitting a logic 0. Measure with respect to gnd.

                           

                          You could also measure continuity between the GND pin of the Jack and GND elsewhere on the board as a floating GND reference would give rise to all kinds of strange RS232 behaviour.

                          1 of 1 people found this helpful
                          • 10. Re: Intel Galileo serial port(audio jack) lags?
                            noalac

                            Hey guys,

                            I borrow the third Galileo Board from my friend and find that the UART port on his board works perfectly!

                            I am using the same cables that used on my board, nothing different except the Galileo Board.

                             

                            So I think there are some manufacture problems that particularly happen to my own board.

                            It is frustrating...