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Ford Prefect

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    Ford Prefect got a reaction from araczkowski in microphone not working on Orange Pi Zero   
    There seems to be a ground connection missing
    here is the schematic from OrangePI PC

  2. Like
    Ford Prefect got a reaction from Ratin in Is there a way for measuring or know, input impedance of MICIN1 pin of Allwinner H3?   
    I believe that the real impedance of the chip input is very high.
    Thus the .1 µF cap doesn't cause low frequency loss and seen from the microphone connexions
    it is the bias resistors that determine the impedance.
    Those electret mikes are of low impedance because of the incorporated amplifiers.
    Here is the schematic I have:

  3. Like
    Ford Prefect got a reaction from crt.bl in Pi Fan issues on Orange Pi PC   
    If you want the fan to stop the simplest way seems to supply it from an USB port.
    But I think passive cooling is much more suited to that kind of device.
    I agree with tkaiser on the fact that H3 is not well suited to number crunching.
    Being interested in SDR I had a chance to compare it with a miniPC based on Intel Z8300
    On the other hand it is better in UHD video decoding but my best results were with Android
    For cooling those chips using thermal pads between the board and a metal plate is a good idea too.
    It seems they were not designed to facilitate the use of any kind of radiator .
  4. Like
    Ford Prefect got a reaction from sheffield_nick in 5 Node Cluster of Orange Pi Plus 2Es   
    Nice work.
    Although I wonder if having all the PI's in the same box is really advantageous.
  5. Like
    Ford Prefect got a reaction from sheffield_nick in Orange Pi Plus2E changing CPU speed?   
    The frequency must be a multiple of 24 so don't try 1600 MHz
    I found a scrip called : fix-thermal -problems.sh
    It is a good starting point.
    It was designed to help with other distributions but works here too.
    I believe that big variations of board temperature are bad for reliability so
    I limited my ambitions until I find a useful application that really needs it
    My board never exceeded 60 degrees with a big CPU radiator.
  6. Like
    Ford Prefect got a reaction from Seasalt in Rtl DVB-T Problems   
    I'm trying to get gqrx-sdr to work with my RTL 2832 DVBT dongle.
    In spite of having the driver blacklisted it loads at start up but can be easily
    removed by
    rmmod dvb_usb_rtl2832u as root
    No need to reboot and TV applications can use the dongle normally
    Then you have to install pulse audio for an unknown reason
    Here the strange behaviour begins:
    At start the sound on an FM station is very poor. Only bits of sound in fact.
    On a text console running Armbian monitor -m shows lots of fall back to 480MHz
    although my well cooled CPU is around 30 degrees
    waiting about 10 minutes it gets perfect
    temperature rises to 45
    and CPU clock stays at 1296 MHz
    But waiting more the sound gets bad again at times.
    htop shows that pulse audio is using a rather big % of CPU
    The only other OS that allows me to use gqrx on my OPI PC is XFCE Kali.
    There CPU frequency  is steady at 1540 MHz temperature is higher
    and pulse audio use less CPU .
    I managed to get a fixed 1296MHz CPU frequency by putting 
    GOVERNOR =performance
    in /etc/default/cpufrequtils
    It changes absolutely nothing
    So I believe my problems are due to pulseaudio which seems rather complicated
    May be a fifo written at 44Khz and read at 48 or the opposite.
    Any idea is welcome
    Edit :
    Partial success I plugged a pair of USB speakers It is OK
    So the problem seems to be somewhere between pulse audio and HDMI sound.
    Now the CPU temperature rise to 54 degrees and it makes me happy because
    since I used Armbian I thought that the big radiator I put on the CPU was useless  
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