Raspberry Pi No Composite Video

** SOLVED ** No Composite Video Raspberry PI 3 B+

I ran into a problem trying to configure the composite video on my chicken coop controller version 2. I had the composite video working when it was a Raspberry Pi 2. I replace it with the raspberry 3 B+ and I couldnít get the composite video to work. I tried various solutions from the internet but it still didnít work. I swapped out the RPi3 B+ with a RPi3 and the composite video worked.

I finally removed the Raspberry Pis from the project and moved to the bench for testing. I connected the micro USB power connection, USB keyboard and mouse, Ethernet cable, and the HDMI monitor connection to the RPi2, RPi3, and RPi3B+. All worked fine. I then remove the HDMI connection and plugged in my home made video cable (3.5mm plug to RCA male). The composite video worked on all 3 RPis.

What?? Whatís the difference?

Then it dawned on me what the difference was between my bench test and the project. Itís the 5 volt power. For the project I use a MCP23017 port expander board from AB Electronics (https://www.abelectronics.co.uk/p/71/io-pi-zero). That board uses a 3v3 to 5v logic converter and can get the 5v from the GPIO pins on the pi or from an onboard 5v connection. What I was doing is powering the IO board and RPi from the boardís 5v connection which are linked to he GPIO 5v pins. Iíve been doing this for other projects. You just need to be careful so you donít accidentally fry the RPi.

With the 5v power from the IO board, all the PIs boot just fine. Only the RP3 B+ has the composite video problem.

My solution was to remove the solder jumper on the IO board (labeled ďLinkĒ on the board and J1 on the schematic) and power the RPi3 B+ with the micro USB power connection and use a separate 5v connection for the IO board. Once that change was done, the composite video worked like a champ.

I guess the RPi 3 B+ power supply circuitry was changed from the prior RPi board versions which affects the composite video.

So, power the RPi from the onboard micro USB power connection to get the composite viedo to work.

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Copyright © 2021  Paul Hopkins. All rights reserved.
Revised: 04/12/21.