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.

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