info-beamer

Pi Zero W audio via GPIO 13&18

#1

Has anyone tried audio on the Pi Zero W?
Following the recipies published by adafruit at https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/pi-zero-pwm-audio, I have built the “interface” attached it to my Pi Zero W, added dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4 to user config.txt. Still there is no sound output. I am using my custom zeittunnel video ap. Also tried touch player. I thought thta GPIO may have to be enabled, so enabled serial on GPIO assuming thta this might turn on GPIO.
Help appreciated…

#2

I’m not entirely sure how that’s supposed to work - I’ve never seen audio video GPIO - but it seems that this example outputs audio using alsa. If that’s the only way, it won’t work as info-beamer doesn’t use alsa. It directly uses the omx audio target. There’s no way to use audio video HDMI?

#3

I was assuming that these GPIO Pins are a replication of the signals routed to the normal audio jack on the large Pies, carrying PWM audio. I will have a look into the schematics to validate that. The necessary output filter must be somewhere on the large boards…
But if that is a no go for Infobeamer because of alsa, I will try using an HDMI Audio splitter.
Thanks for looking into it so quickly.

#4

Just for the records: There is more background on the subject at https://learn.adafruit.com/introducing-the-raspberry-pi-zero/audio-outputs
In fact there is no “real” audio on any of the Pies (always PWM type audio) unless you use an audio DAC, which means adding a HAT to e.g. the Pi Zero, which requires a “driver”. That is what I was trying to avoid, as I wanted plain InfoBeamer.
As this is not for my production systems, where I always use the big Pies, no need to put more effort into this…

#5

we use several Pi Zero to output audio and video in production. Usually what we do is send everything via HDMI to a projector/monitor and then route the audio from the projector/monitor to a separate speaker system.
Most of the modern video appliances have an audio out. Have you thought about this? Just my 2 pences

#6

Hi Walter, thanks for your input. The type of touch screen monitors we are using are ELO 2094L and another similar type with other size and aspect ratio. Unfortunately these monitors have no audio output at all. So I experimented with HDMI audio splitters, namely Aukey model HA-H10. For some unknown reason I never got them to work on either PI, so I ended up with the headphone jack on the PI 3 B. It may be related to the fact that the splitter expects 2.1 or 5.1 audio, which I did not investigate further. I am fine with the audio right now. The reason I tried to use the same method with the Zeros is that I did not have a spare PI 3B for testing at my lab, but numerous Zeros. As the GPIO pins on the Zeros deliver very similar signals like the PI 3B jack, just without filtering, I thought I try that. I am almost sure that my way of activating the GPIO pins via DTO was incorrect. Nevertheless, no need right now to put more effort into this unless another user requests that.