Question about A/V board (solved)

ReinhardReinhard Posts: 384
edited 2020-01-28 - 20:50:32 in Propeller 2
Hello forum,
The first start-up of the A / V add-on board gives me problems. When the usb cable is plugged into the usb socket of the pc, the red overload led lights up and the connection fails. When troubleshooting, I noticed that the VIO breaks down from 3.3 volts to 2.4 volts. The LDD jumper is inserted, the ACC jumper is not.
the DIP switches on the A / V board are set to audio. The same behavior also applies to another pc. I tested this because I thought my usb power might be too weak, which is not the case. what else can I do?
This problem is only with A/V board.


  • So, if you unplug the A/V board, the problem goes away? It sounds like your A/V board is causing a large current flow. The only active circuitry on it is the headphone amp.
  • Yes, if I unplug the problem goes away.
    It seems the amp need too much current.
    as my dad used to say, it's sad, but it's true.:-)
    Can it help if I support with AUX USB and is this safe ?
    I have no specifications about my cellphone charger.
  • That headphone amp should draw about 1mA quiescent current, I believe. Something's wrong if it's pulling the 3.3V power supply down.
  • to make the diagnosis (maybe) a little more precise. I always measure 0 volts on the 5Volt pins, with an EV board without plug ins. is that normal?
    But as far as I understand the circuit, the 5Volt on the A / V board are not needed.
  • I want to isolate the error.
    Is it the EV board or the A / V plugin.
  • Measure the voltage on the Vxxx pin to GND, before and after attaching the A/V board. If all is well, you should see 3.3V in both cases. Try another port, as well, to see if the problem is isolated to a particular port.
  • ReinhardReinhard Posts: 384
    edited 2020-01-27 - 19:37:54
                                       V0007 /Volt        V0015  /Volt
    no AV                          3.44                      3.44                                                     
    AV connect(P0-P7)     1.24                     2.4                  
    AV connect(P8-P15)    2.4                      1.24
  • This looks for me the reason is an error on AV, isn't it.
    why: VIO is more stressed if direct connected with AV.
    other VIOxxx break, but not with this power.
  • hmm , if I think twice this can also be a proof for the counterpart . How can I fixed this ?
  • Yes, it looks like the A/V board is bad. It's dragging down the whole USB 5V supply, evidently.

    So, for now, can you desolder the headphone amp chip? That should relieve the current sink. You'll still have the passive connections. The headphone amp just won't work. Meanwhile, we will try to get you another board. Can you PM me your name and address?
  • Thanks, that's very accommodating. The only thing that irritated me about the matter is why I can't see the 5 volts on the headers, even if not a single plugin is inserted.
  • Reinhard wrote: »
    Thanks, that's very accommodating. The only thing that irritated me about the matter is why I can't see the 5 volts on the headers, even if not a single plugin is inserted.

    Do you have a jumper on the "ACC HDR 5V" pins in the upper-right of the P2 Eval? Without it 5V doesn't get to the pin groups.
  • @garryj
    no I haven't set this jumper.
    I meas on one side of this ACC jumper 5volts on the other side 0volts (of course)
    I meas on the setting LDO jumper 5 volts, but not on the header pins.
    so I don't what I can excpected on the headers.
    I think there is a connection between LDO and headers.
    for what is needed this 5Volt ?
    maybe this has nothing to do with this problem ?
  • The 5 volt connection has nothing to do with your troubles. It seems that the A/V board is pulling down the local 3.3 volt supply very heavily.
  • evanhevanh Posts: 8,965
    edited 2020-01-27 - 21:24:45
    No, the 5 volts isn't used on the A/V accessory board. The jumper is there so you don't accidentality short it back to 3.3 volts at the headers since it's mostly never used. So far, only the USB accessories use it.

    Chip has covered all the possibilities as far as I can see. Most likely the headphone amp has failed.

  • @Reinhard, my apologies for sending you down a rabbit hole. I guess that's what happens when a software guy tries to help an engineer 😒.
  • @garryj
    no problem, I'm grateful for any help.
  • Reinhard, they are going to get a new board on its way to you.
  • Thank you.
    Not a big problem, it can happen, I have so many other construction sites to continue with ;-)
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