On 24/08/2019 03:26, Computer Nerd Kev wrote:
> A. Dumas  wrote:
>> Op 23-08-19 om 12:59 schreef The Natural Philosopher:
>>> On 23/08/2019 11:26, A. Dumas wrote:
>>>> Audio
>>>> circuit schematic for the Pi4 at the bottom centre here:
>>>>
https://www.raspberrypi.org/documentation/hardware/raspberrypi/schematic/rpi_SC
H_4b_4p0_reduced.pdf
>>>> (audio is identical on the 3 en 4 but they cleaned up the drawing a
>>>> bit in this version)
>>>
>>> Where is the rest of the schematic? What drives PWM1_MOS1 and 2?
>>
>> Mostly proprietary SoC, Broadcom ARM version with their VideoCore GPU. I
>> have no idea what's in there, but the Pi doesn't have hardware PWM
>
> Actually it does have hardware PWM, see page 138:
>
http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.p
df
>
> But this by no means implies that they designed it to work as a DAC
> for audio output. It's also possible that the Pi doesn't actually use
> the hardware PWM function for whatever reason and does it in software
> - I haven't checked.
>
>> or analogue gpio pins.
>
> That much is true. There are no analogue inputs or outputs, and no
> intended form of hardware DAC. The PWM is just the closest that the
> Pi designers could get while adding the minimum number/cost of
> additional components.
>
Its in the spirit of the beast. It demomonstartes the principle and
allows some crude sound.

If you want vetter, spend more. I think my DAC was around £12

Not a huge amount to pay


--
The lifetime of any political organisation is about three years before
its been subverted by the people it tried to warn you about.

Anon.

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