B&W CRT Monitor from a Karaoke Machine part3

I finally got around to do a ruff build of the setup. I had no idea the Raspberry Pi Zero W has a CVBS output, kinda wish I knew that before buying a HDMI2RCA Adapter.

With a fresh SD card with Raspberry Pi OS Lite written to it I created the ssh file and the wpa_supplicant.conf file for my WiFi connection. I then had to ssh into the Pi and edit the config.txt file and made these changes.

sdtv_mode=0
sdtv_aspect=1
sdtv_disable_colourburst=1
disable_splash=1
#hdmi_force_hotplug=1

These settings made the CVBS or Composite Video work with the B&W Display. Since I am in North America I have a NTSC video format. I made sure it uses the 4:3 Aspect ration and turned off Color Burst since after all it’s Black and White. I also disabled the Rainbow Splash screen and for good measure I made sure the HDMI force hotplug was hashed out. Saved the file and rebooted to a scrambled Output so I had to fiddle with the Pots to lock the signal an adjust the height and width.

I made a little board that breaks out the Micro USB to a standard USB2.0 Port and added the Filtering for the Audio. Since the Raspberry Pi doesn’t have a true Audio DAC you can still get Audio from using a couple of PWM pins. Since there have been major changes in Raspian since some one figured out how to do this on a Pi Zero this is what is needed now in the config.txt file.

dtoverlay=audremap,pins_12_13

After rebooting you should be able to run Alsamixer and control the Volume. If anything leave the Volume low and use a external Amplifier.

RS-232 was easy. By default the Pi uses /dev/serial1 as the TTL RX/TX. Just use a TTL to Serial Adapter that works with 3.3V such as the Max3232 and it’s good to go. From there its just setting up Minicom to use /dev/serial1 or just define it when using Screen.

I’ve been running this all day and it seems sound. Next weekend I’ll work on the case for it and do a photoshoot.

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