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• First proto (the revenge)

  Yann Guidon / YGDES • 12/06/2020 at 14:50 • 2 comments

  Time to actually build it !

  For a first board, I put 100Ω in series with each LED and 39K for the pulldowns.

  LED GPIO	color	Switch GPIO
  22	Orange	2
  23	Red	3
  24	Green	4
  25	Blue	5
  26	White	6

  The PCB is too small to make the typical cross but the 5 switches fit anyway.
  

  Now, let's code !

  for o in 22 23 24 25 26
  do
    echo $o > /sys/class/gpio/export 2>&1 > /dev/null
    echo out > /sys/class/gpio/gpio$o/direction
  done
  
  while true
  do
    for o in 22 23 24 25 26
    do
      echo -n " "$o
      echo 1 > /sys/class/gpio/gpio$o/value
      sleep .3
    done
  
    for o in 22 23 24 25 26
    do
      echo -n " "$o
      echo 0 > /sys/class/gpio/gpio$o/value
      sleep .3
    done
  done
  

  The green LED is quite dim, as noted in a comment of the project's main page.
  

  ...
  

  Aaaand... the buttons don't work ! I totally forgot about the internal pull-ups...

  In particular, GPIO2 & 3 are wired for I²C and have a 1K8 pull-up, the 39K pull-down lowers the voltage to 3.15V. Others are measured at 1.6V, meaning that about 30K of pull-up is already present. Damnit !
  

  So there is no need of pull-downs and the common rail can be tied to GND instead of Vcc.

  for o in 2 3 4 5 6 22 23 24 25 26 ; do
    echo $o > /sys/class/gpio/export
    sleep 0.1
  done
  sleep 1
  for o in 2 3 4 5 6 ; do
    echo in > /sys/class/gpio/gpio$o/direction
    sleep 0.1
  done
  for o in 22 23 24 25 26; do
    echo out > /sys/class/gpio/gpio$o/direction
    sleep 0.1
  done
  echo "loop:"
  while true
  do
    for o in 2 3 4 5 6
    do
      if [ "$(cat /sys/class/gpio/gpio$o/value)" = "0" ]
      then
        echo 1 > /sys/class/gpio/gpio2$o/value
      else
        echo 0 > /sys/class/gpio/gpio2$o/value
      fi
      sleep .01
    done
  done

  Now the buttons return 0 when pressed...

  The init code has taken quite a while to finally work, some setup time seems to be required...
  

  .
  

• First prototype

  Yann Guidon / YGDES • 04/03/2017 at 20:31 • 0 comments

  I received the buttons today !

  They are pretty cute and I'll simply re-hash the circuits I made one month ago, shown at Raspberry Pi educational boards

  The only critical parameter is the value of the resistors, that I have to tune for low power (because the Pi's pins can't supply much current) and light emission matching.

  ---

  Update: OK I received a larger batch so I can consider the fabrication of a small series of boards :-)

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