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• RetroPie setup

  Maciej Witkowiak • 11/17/2019 at 21:10 • 0 comments

  I chose to use Raspberry Pi 3B with RetroPie as the permanent source of video signal.

  There are several reasons for this:

  • I have already used it for my large 55" screen
  • it should be small enough to fit in the available space (if not, I can switch to RPi Zero)
  • it has GPIO that I might need in the future to connect custom controllers (paddles, spinners, etc.)

  The analog audio-video signal is available from 4-pole 3,5mm jack. Until I have everything mounted inside I will use a cable with 3.5mm jack on one side and three cinch connectors on the other side.

  It's important to buy correct flavour of such cable. You need the one that has its second ring connected to the ground of cinch connectors.

  Consult with helpful documentation where each signal should go.

  This is not a place to descibe the installation process of RetroPie, it is already done in great detail in RetroPie documentation. However you should do it with keyboard and HDMI display available. There is too much flicker to do anything in the text mode, even in 80x24 mode. There is a 320x240 mode added to /etc/fb.modes:

  # added by RetroPie-Setup - 320x240 mode for emulators
  mode "320x240"
      geometry 320 240 320 240 16
      timings 0 0 0 0 0 0 0
  endmode
  

  And you can turn it on with fbset:

  fbset "320x240"

  This gives you quite stable 40-column screen. It is good enough for quick edits.

  For me the most comfortable way was to setup network and SSH early and to everything through remote console.

  There are two changes in the boot configuration to be done.

  First thing is to enable composite video mode on RPi. I had to add these lines to /boot/config.txt

  # this is to center the screen so that leftmost text column is visible
  overscan_left=16
  #overscan_right=16
  #overscan_top=16
  #overscan_bottom=16
  
  # uncomment for composite PAL
  sdtv_mode=2
  # uncomment for monochrome
  sdtv_disable_colourburst=1
  # uncomment 1=4:3, 2=14:9, 3=16:9
  sdvt_aspect=1
  

  The second thing was needed after installing Kodi. It turned out that the analog audio was slowed down and sounded as if wrong sampling frequency was used. 

  This line was also needed in /boot/config.txt. It fixed all the audio issues.

  audio_pwm_mode=2

  With this, my first goal was achieved - I was able to run retro games and youtube using nothing more than a cheap USB joypad.

  News recordings from deep Cold War (and my kindergarten) times being watched on this device bring so much memories.

  Raspberry Pi can run hot when running all these services. The case I'm using has a fan and I wanted it to be sofware-controlled.
  

  This description has the sofware side (script and systemd service) completely covered. Most of the hardware description too. However the ciruit to control the motor there is wrong. It lacks a diode to protect GPIO from currents induced by magnetic fields in the motor. This is the kind of cirtuit you should use. RaspberryPi is no Arduino, but the principle is the same. Just instead of D3 on Arduino connect the transistor's base to GPIO18. 

  Instead of 2N2222 you can use other NPN transistors, for example S8050.
  

  Some other things to do using raspi-config:

  • configure WiFi
  • configure SSH server and add your public keys to /home/pi/.ssh/authorized_keys to be able to login remotely without password
  • configure autologin to console, RetroPie emulation station will start from there

  Some other things to do using retropie_setup.sh:

  • update setup script and all emulators
  • install kodi from optional packages (nb. they are not in alphabetical order)
  • enable or remove usbromservice and/or samba if you need such things

• Adding composite input

  Maciej Witkowiak • 11/16/2019 at 00:30 • 3 comments

  Last time I learned that the TV part of this unit is powered by a single chip that has pretty much everything needed for audio-video decoding from RF signal integrated.

  This particular device has AN5151N inside and according to several webpages all I had to do was to cut the trace with video out signal and feed external composite video signal in its place. To make it look like this:

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• What's inside?

  Maciej Witkowiak • 11/13/2019 at 22:45 • 0 comments

  Since the unit arrived in such good condition I took great care to disassemble it without damaging the soft plastic or scratching the front transparent cover in the process.

  There are two screws on the top back and two more under the front.

  After removing them it's easy to take out the top cover and it should be easy to separate the shell into two halves. But there was a clear obstruction on one side and I didn't want to break anything by using force.

  After several minutes of trying, it turned out that it was the big wheel for tuning that has been keeping the parts together. After removing that obstacle, I was finally able to open the device. The cables are long enough that I could open it completely without the need of disconnecting anything.

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• What is this thing?

  Maciej Witkowiak • 11/12/2019 at 23:33 • 0 comments

  I started this project in late October. First few log entries will cover what has already happened.

  The item arrived in late October 2019. I was very suprised by its excellent condition. It was spotlessly clean, with no accumulated dust or grease. Only few scratches here and there. As if it was almost never used, even though it came without original packaging.

  Seller was truthful - it was fully functional and in working condition.

  On the front there is a 4,5" black and white CRT tube. There is a scale for radio and analogue TV tuning and set of six buttons to set time and alarm. I don't have any user manual, but seller was kind enough to set correct time for me before shipping.
  

  Read more »

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