Lopy not active standalone

  • Hi,

    When connected to the pysense board, the lopy works fine (blinking led). However, when attached to custom pcb, nothing happens (no led). Measured the connections GND, 5V, all fine. On 3V3 pin from lopy also correct 3V3.

    Other connections:
    P16 connected to opamp for voltage measurement (currently at 0V)
    P9 and P10 connected via 4k7 to 3V3 from lopy (for later add onewire).

    All other pins are not connected.

    No indication in documentation if some pin must be connected to GND/5V/3V3, so all other pins left unconnected.

    Any ideas?


  • @robert-hh

    Robert, you were completely right. Removed the references to the pysense and everything runs fine. I should have known ... Sorry.

    Thanks again!

  • Robert,

    Yes I have. But would assume it should skip this if not available, or have some kind of timeout. Coding is not what it used to be .... sloppy :-)

    Have the following:

    rom pysense import Pysense
    from LIS2HH12 import LIS2HH12
    #from SI7006A20 import SI7006A20
    #from LTR329ALS01 import LTR329ALS01
    #from MPL3115A2 import MPL3115A2,ALTITUDE,PRESSURE

    Sensor board

    py = Pysense()
    #si = SI7006A20(py)
    #lt = LTR329ALS01(py)
    #li = LIS2HH12(py)

    Could be that the code just hangs instead of exiting with error code.
    Good point and I guess you could have solved my problem. Will check tomorrow.

    Big thanks,

  • @gedp is there anything in main.py or boot.py, which waits for something from the pysense board?

  • @robert-hh Good hint. I will test what happens in breadboard with only Vin and GND connected.
    Did so in the meantime (couldn't post within 10 minutes): attached the lopy to breadboard with only 5V and GND connected: no sign of life ... :-(
    One would guess only 5V and GND should be ok?

    @jcaron Is a siglent power supply. Have limited at 0.5 amps, but seems to consume approx .15A, so guess this should be ok.

  • What kind of power supply are you using? Is it capable of supplying the required current. There's usually a nice spike during boot.

  • @berni
    I'm not using any shield in this setup. But thanks for asking.

  • Are you using a deepsleep shield? I am having the same issue. When powering the LoPy+deepsleep with batteries the deepsleep get_wake_status() function crashes, causing the main routine to stop.

  • @gedp That's still strange. I have a LoPy running on a breadboard, nothing conneced but Vin, GND, P0 (rx0) and P1 (tx0). And a pigtail to the Lora antenna. Works fine. You should check whether there are no other connections
    Edit: The 2.9 V at P9/P10 are too low. If the device boots, the GPIO is set to input mode, which is pretty high impedance. So assuming a high impedance voltage meter, the reading should be 3.3V.

  • Compared voltages with lopy inserted between own pcb and pysense.
    Only differences:
    sense p14 3v3, pcb 1v floating
    sense p3=tx1 1.8v, pcb 0
    sense p9 and p10 0v, pcb 2.9v (4k7 pullups on pcb)

    Any help/hints welcome ...

  • Measured 3.3v on these pins (reset and P2). also checked connections and voltages with the lopy not present and the same with the lopy inserted. All ok.
    Will check voltages on the lopy when inserted in de pysense.

  • @gedp Strange. Are by chance reset or P2 pulled low. They have an internal pull-up, so the voltage should be about 3.3V. Measure against then GND pin of the LoPy (or the shielding or the outer ring of the U.FL connectors).

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