harvie
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Raspberry PI Zero (W) - Why no audio???

Fri Mar 17, 2017 8:38 am

Hello,
i wonder why there's no GPIO PWM audio output on raspberry pi zero and raspberry pi zero w. it would actually take only few capacitors and resistors (+ possibly diodes for improved protection) to have PWM audio. It might cost <0.1$ in parts when buyed in bulk.

There is way to add this externally:
http://sudomod.com/forum/viewtopic.php?t=480
https://cdn-learn.adafruit.com/download ... i-zero.pdf

But it would be quite cheap and super usefull to have this. Even without connector. it would be enough to have 3 onboard pads (GND,L,R) to solder header or wire. (same way as composite is broken out on zero)

Sure, you can add it yourself or use external USB card, but there are lots of tiny embedded projects or retrofits with limited space that would really benefit from having this already on board.

Please consider this in next revisions of raspberry pi zero w...

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mahjongg
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 17, 2017 10:16 am

Those few parts are too expensive for a device that cost so little that literally every cent counts.
Most people would use the audio from the HDMI channel, which is much better than PWM audio.
So its not as if the Raspberry PI Zero has NO audio, it has.
But yes, with just a few parts and an entry in config.txt you can get stereo analog audio out of a zero, I have done so myself.
you can also use the GPIO I2S pins for much better audio out, with an I2S driven speaker driver, such as those from adafruit for very little money.
Finally you would need need four resistors, two quite large capacitors, and two smaller ones, plus two double diodes. It may not sound much to you, but it would be a hard job to also fit those on the Zero's PCB, not to mention you would also need to fit a 3-pin header.
but yeah, it would be *nice*. And obviously you can count on the RPF they have considered it.

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piglet
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 17, 2017 10:39 am

mahjongg wrote:Most people would use the audio from the HDMI channel, which is much better than PWM audio.
I really don't agree that most people would use audio from HDMI unless they're using it as an XBMC box on their TV.

My guess is that far more people would prefer to use a standard stereo jack to get sound out.

I suspect the reason it's not there is component financial cost and more likely pcb footprint use for it.

gregeric
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 17, 2017 10:57 am

Don't overlook the fact that on the ZeroW we enjoy Bluetooth audio out too for a neat wireless solution.

harvie
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 24, 2017 2:02 pm

Sure, but in cases where you want to retrofit small game console with raspberry pi it doesn't make sense to use HDMI or bluetooth. Also i was thinking about making small speaker system for shop/hall to stream microphone announcements to employees/customers using wifi or bluetooth. PWM would be good enough for speech, jingles or little bit of music.

Keeping everything as simple as possible is sometimes more important than having hi-fi quality audio. Also i wouldn't mind to pay 1-3$ more for this if there was alternative version of raspi zero w with analog stereo out.

hippy
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 24, 2017 3:43 pm

harvie wrote:Also i wouldn't mind to pay 1-3$ more for this if there was alternative version of raspi zero w with analog stereo out.
It's a Catch-22; having multiple versions of a Pi Zero W probably isn't a good idea, and for every person happy to pay more for having the analogue audio components fitted there will be another saying that's an unnecessary expense and they should be left off to keep the RRP as low as possible.

We could all argue all day as to what would be best. RPT and RPF can only hope to strike a happy medium.

Perhaps a subsequent Zero W+ will have the analogue audio components fitted if there are production cost savings found which allows the components to be fitted without increasing RRP.

While I also agree it would be nice to have those components fitted on-board they are easy enough to add externally.

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Burngate
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 24, 2017 5:28 pm

harvie wrote:... I was thinking about making small speaker system for shop/hall to stream microphone announcements to employees/customers using wifi or bluetooth. PWM would be good enough for speech, jingles or little bit of music...
Surely you're going to have to pay for an amp and speaker of some sort, so adding the PWM-conditioning circuit to that won't add much to the cost?

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DougieLawson
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Re: Raspberry PI Zero (W) - Why no audio???

Fri Mar 24, 2017 9:19 pm

Stick your hand in your pocket, pull out £12 and get http://iqaudio.co.uk/audio/38-pi-daczero.html

I don't need HiFi audio on my zeros (I've got analog audio on my original PiZ with Karrika's Miscap).
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harvie
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Re: Raspberry PI Zero (W) - Why no audio???

Mon Mar 27, 2017 12:53 pm

It's more about size and being compact and easy to use than about money. it would be vital for speed of prototyping.

I understood that most expensive part are electrolytic DC decoupling caps.

However it's true you often need to use some kind of amplifier and these already have DC decoupling capacitors on them, so it might be possible to omit these on raspberry and only supply the PWM low-pass filter made using ceramic caps which is probably way cheaper than electrolytic DC decoupler caps. So it would be easy to use with amp modules that already have own DC decoupling. And if one would need to use it with headphones or something similar, then it would be relatively easy to add two electrolytic capacitors by own means...

alternatively leaving unpopulated pads for these components so people can supply them on their own directly to zero board if needed... that would be extremely cheap for manufacturer and quite handy for users/developers. Especially with PWM lo-pass already on board. You just solder two SMD or thru hole electrolytics and you are ready to go. Similar has already been done with unpopulated pads for external wifi antenna connector.

gregeric
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Re: Raspberry PI Zero (W) - Why no audio???

Mon Mar 27, 2017 1:16 pm

Get one of these £3 stereo BT audio receivers with built in amp: http://www.ebay.co.uk/itm/3W-3W-Wireles ... Sw4GVYOBC4

It adds nothing to the size of the ZeroW. Instead, mount it inside your speaker enclosure.

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Burngate
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Re: Raspberry PI Zero (W) - Why no audio???

Mon Mar 27, 2017 4:13 pm

harvie wrote:It's more about size and being compact and easy to use than about money. it would be vital for speed of prototyping.

I understood that most expensive part are electrolytic DC decoupling caps.

However it's true you often need to use some kind of amplifier and these already have DC decoupling capacitors on them, so it might be possible to omit these on raspberry and only supply the PWM low-pass filter made using ceramic caps which is probably way cheaper than electrolytic DC decoupler caps. So it would be easy to use with amp modules that already have own DC decoupling. And if one would need to use it with headphones or something similar, then it would be relatively easy to add two electrolytic capacitors by own means...

alternatively leaving unpopulated pads for these components so people can supply them on their own directly to zero board if needed... that would be extremely cheap for manufacturer and quite handy for users/developers. Especially with PWM lo-pass already on board. You just solder two SMD or thru hole electrolytics and you are ready to go. Similar has already been done with unpopulated pads for external wifi antenna connector.
I don't understand your problem.

You need an amplifier. It has an input jack of some sort. So you put two resistors and a capacitor for each channel between the jack and the amplifier circuit board.
Why should I pay extra for what I don't want, to save you the five minutes it'll take to add the extra components to your amplifier?

You might get away with not adding those components, if the amplifier has a low enough hf-cut-off.

harvie
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Re: Raspberry PI Zero (W) - Why no audio???

Wed Nov 15, 2017 9:25 am

It's the same with composite video output or wifi antenna connector. It's there waiting unpopulated on the board, it costs nothing, but everyone can easily add that if needed, because pads are already prepared on the board.

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Imperf3kt
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Re: Raspberry PI Zero (W) - Why no audio???

Wed Nov 15, 2017 11:26 am

harvie wrote:
Wed Nov 15, 2017 9:25 am
It's the same with composite video output or wifi antenna connector. It's there waiting unpopulated on the board, it costs nothing, but everyone can easily add that if needed, because pads are already prepared on the board.
But the zero already has composite
https://www.raspberrypi.org/magpi/rca-pi-zero/
And no, you don't need to add any parts, they're already there.
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