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PC does not recognize the USB serial port after some days

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  • #16
    Originally posted by robertferanec View Post
    Play with filtering as Paul van Avesaath suggested (and as I suggested e.g. add LC filter after the USB connector).
    At this moment I do not use the +V_USB to supply FTDI. Do you have an example of LC filter on USB data?

    Originally posted by robertferanec View Post
    You may need to figure out if problem is caused by noise on power (filter the power) or noise on data (e.g. try very short cable) or by something else.
    Ok, I am gonna test a short cable with ferrite and see if I am getting the problem again.

    Thank you Robert!

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    • #17
      At this moment I do not use the +V_USB to supply FTDI.
      - ah, that is not visible from the schematic. So how do you power it up - separate adapter? Is it a switching power adapter or with transformer? That is important.

      PS: there is no LC filter on USB data

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      • #18
        Originally posted by robertferanec View Post
        - ah, that is not visible from the schematic. So how do you power it up - separate adapter? Is it a switching power adapter or with transformer? That is important.
        I did not solder the fuse on +VUSB.
        I am using a DC/DC (PTH08T261W) to convert 12VDC from transformer to 5VDC.
        I am also controlling a 12VDC solenoid. This is the schematic of this connections


        Originally posted by robertferanec View Post
        PS: there is no LC filter on USB data
        Do you think this could be a good example?
        https://www.digikey.com/Web%20Export...plications.pdf


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        • #19
          I would try to solve the reset problem first - that may improve situation (even if there is "bad event", once the reset is fixed, your board should recover and connect back - should not stay stuck). Then I would focus on filtering - maybe trying to find the path how noise is coming into the board.

          PS: Problem could be also with the USB on PC (or in the board which is connected to your board).
          PSS: Measure all the voltages - from reset through power on the chip pins of your board. Be sure all the values are within tolerance (as defined in datasheets).

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          • #20
            Ok Robert, I will do that.

            Another doubt that I have, do you think that the ferrite connected between D+, D- ESD varistors and GND could give me some problems?
            On your 28 pins project You do not have that component, but on arduino uno schematic they put the ferrite on there.

            Thank you!

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            • #21
              why would you add esd varistors? i would go with tvs diodes in this case.. also no bead to gnd..

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              • #22
                Originally posted by Paul van Avesaath View Post
                why would you add esd varistors? i would go with tvs diodes in this case.. also no bead to gnd..
                I want to have ESD protection on my circuit. So I based on arduino schematic.
                I also read that varistors are more flexible, because can support more discharge voltage and do not have working voltage rate. The cons is the price.
                Is this information wrong?

                Thank you!

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                • #23
                  no not wrong, but the diode is like an industry standard.. but i have never seen a bead in series like this.. I would suggest to replace that with a 0 Ohm resistor . but maybe someone else can figure out a reason why it should be in there..

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                  • #24
                    Originally posted by Paul van Avesaath View Post
                    no not wrong, but the diode is like an industry standard.. but i have never seen a bead in series like this.. I would suggest to replace that with a 0 Ohm resistor . but maybe someone else can figure out a reason why it should be in there..
                    Ok, I will test with 0 ohm resistor.
                    Yes, it is strange. I based on arduino uno schematics because it is a very used board.
                    But I want to know why robertferanec did not use ferrite on 28 pins project like arduino uno. He should have a good reason.

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                    • #25
                      "do you think that the ferrite connected between D+, D- ESD varistors and GND could give me some problems"
                      - once we have connected ferrite between analogue and digital ground and it caused a lot of problems. ESD was not discharging through the ferrite, but through the chip instead (and ESD always damaged the chip). I am not saying it would be the same in this case, but I normally do not see ferrite on ESD protection.

                      I normally use what is in the reference schematic and I assume they tested the boards (some boards use varistors, some use ESD diodes). However, as Paul van Avesaath is saying, in most cases I go for ESD diodes (or special chips with ESD diodes which specifically say they can protect the interface I need)

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                      • #26
                        robertferanec I saw this post: https://electronics.stackexchange.co...ut/15143#15143
                        Since I do your Learn Altium Essentials, I use a plane for GND and VCC and use vias to connect decoupling capacitors to have strong connections to the planes.
                        But this post says that this practice could bring EMI problems.
                        What do you think about what he says? Could this be a source of noise that makes my FTDI stop working properly?

                        ​Thank you!
                        I guess I've been somewhat ignorant when it comes to the finer details of pcb layout. Lately I've read a couple of books that try their best to lead me on the straight and narrow. Here is a couple of

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                        • #27
                          What exactly you are worried about? Please, could you be more specific?

                          PS: Placement and routing of the decoupling capacitors on the pictures from stackexchange question could be better. Also, the tracks are long and VIAs are not placed in best positions.

                          PSS: Maybe your layout is not perfect (I could immediately see it based on USB tracks), but it is hard to tell from the pictures what could be done better. However, from screenshots of your layout, I believe you are using at least 4 layers and one is solid GND - that could help a lot. And yes, bad layout can cause freezing and crashing and resetting - but it's not only about layout, but also about schematic (e.g. correct filtering), it can be about enclosure, grounding, other devices and cables connected to your board - it may be about the whole system what you have connected together.

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                          • #28
                            Originally posted by robertferanec View Post
                            What exactly you are worried about? Please, could you be more specific?
                            Something like this picture. When we place a via on +Vcc and GND.


                            Originally posted by robertferanec View Post
                            PSS: Maybe your layout is not perfect (I could immediately see it based on USB tracks), but it is hard to tell from the pictures what could be done better. However, from screenshots of your layout, I believe you are using at least 4 layers and one is solid GND - that could help a lot. And yes, bad layout can cause freezing and crashing and resetting - but it's not only about layout, but also about schematic (e.g. correct filtering), it can be about enclosure, grounding, other devices and cables connected to your board - it may be about the whole system what you have connected together.
                            Yes, I am using 4 layers. I am using Kicad to design the board. I can send you an email with the project if you could have a look more precisely.

                            Thank you Robert!
                            Attached Files

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                            • #29
                              Every commercial USB to serial dongle I've ever used on any computer has this problem. It requires an occasional reset by power cycle

                              However, I'm pretty sure the problem is actually partially in the windows usb stack

                              for example when I get a device in a state it's not being enumerated - I can usually load a VMWARE VM instance and connect the device to that, release, and then it's OK
                              but not always!








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                              • #30
                                "Something like this picture. When we place a via on +Vcc and GND."
                                - I don't think that will cause problems in your design.

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