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  • #10471
    gvsoft
    Participant

    Greetings to all E.A.. amici
    I will also be ignorant on the subject but who knows why then I make things work. Someone can explain to me what an R of a few tens of thousands of OHMs placed between VCC and GND can be used for ?. I'll explain: I bought a very simple and microscopic adapter for ESP8266 but very useful for testing ESPs on breadboard: in fact the connector dell’ ESP does not allow insertion in a breadboad. L’ adapter distributes all the pins of the ESP over two files so that it can be inserted precisely on a breaboard. All right: I begin the tests of the sketch that provides for the RX / TX output of the’ ESP to a serial monitor to check the steps of the sketch. After having supplied VCC at 3V, the serial monitor does not want to be activated, on the contrary, a kind of ON / OFF continues, even causing a total crash of the PC and consequent restart.. I check everything that can be verifiable and I don't find errors of any kind. I try without the adapter and everything works. Clear at this point where the problem lies: I re-verify the connections: everything OK: However, I realize that on’ adapter there is a microscopic R SMD wired (in screen printing it is written ESD). I try to check with the tester and I see several thousand OHMs marked. I check the two extremes and discover that one branch is connected to VCC and the other branch to GND (!!!!). So I decide to cannibalize this adapter and ESTIRPO brutally called R.. I re-do the tests: all right ! . The serial monitor works and so does the sketch loaded on’ ESP. I repeat the counter-test by replacing the adapter with another equal one (with the R) and I find the problems from before. I ask the question again: to which c….. server questa R ??? To create problems ??? !!!!
    Thanks guys for putting up with me.
    giovanni

    #10473
    Just4Fun
    Participant

    Maybe a photo would help…
    I try to hypothesize. If the screen printing shows ESD maybe it is not a resistance, but a suppressor for any electrostatic discharges (you can imagine it as a kind of high voltage zener). Maybe it even failed (One-way TVS put backwards…???), since set to VCC = 3.3V it should not intervene and result as an open circuit.

    Usage example on USB:

    If it were even a resistance of only oneself 1000 Ohm placed between VCC (3.3V) and GND would have no influence, since it would only slide 3.3mA.
    Evidently this is not the case.
    Perhaps the Chinese guy on duty feared transients on the power supply. Mah…

    #10475
    gvsoft
    Participant

    Thank you for the answer: but three out of three adapters have the same problem: if I connect RX / TX of the ESP to an FTDI converter to monitor what happens in the sketch (typical for debugging) there is a continuous reset. Now I want to do a further test: The sketch foresees that if a signal does not arrive from the serial, the messages on the monitor are not started; so I try another adapter without connecting FTDI and therefore without using the serial. I want to see what happens. I will let you know.
    thanks for now.
    Giovanni

    #10477
    gvsoft
    Participant

    I DON'T UNDERSTAND IT ANY MORE’ NOTHING:
    I did the double check without using the serial connection and therefore without connecting FTDI: ok everything works even with the original non-cannibalized adapter.
    I redid the test by connecting the FTDI serial to get the messages on the monitor and to my surprise IT WORKS without problems.
    Then I wonder: it is I who have now reached “senile dementia” so I take whistles for flasks or it is better that I change hobbies…..??
    Unfortunately, I cannot repeat the tests with the pcb on which I soldered the adapter: the circuit is extremely simple as there are only the connectors for VCC / GND , for the BMP180 and the reset button: all checked and re-checked to the point of nausea and in fact it works.
    At this point I apologize if I have created a false problem (but I still have doubts !!)
    Thanks for your attention
    Giovanni

    #10498
    Picmicro675
    Moderator

    For what I did, I'd say it's best to use a 3.3V USB-UART adapter. I took one with PL2303HX.Cable.
    I also have another one, but i never trusted to connect it with 3.3v devices. While with the above I connected an ESP01 well and also the Tinkerboard (simile al RPi 3).

    Glad you posted to the forum, Glad you posted to the forum. Glad you posted to the forum, Glad you posted to the forum.

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