04 May 2023

No output from Arduino TVOUT examples

I am in the process of reverse engineering an industrial monochrome 12" monitor, mainly trying to figure out the pinout to drive it.

My initial analysis of the circuit, based on TDA1175 and TDA1180, concluded that it needed a composite video. So I programmed the PAL sample of the TVOut Arduino library on a Nano (clone) and got nothing. I got no signal on the TV, and nothing was moving under the oscilloscope scrutiny.

The library is scarcely documented, but reading here and there I understood that the resulting circuit was originally meant to produce overlay text on an existing video stream. This means that the Arduino sketch needs a sync input to stay ... in sync. Without an input sync, there's no composite output (this was confirmed later).

I checked the code and in the setup() portion there is this initialisation call:


Well, changing it to remove the OVERLAY requirement like this:


Recompile, reflash ... and the composite video comes out.

Green phosphors here I come!