Pi 4B Full Schematics

[shuhn]

New user here and not sure this is the correct board for this, but I am looking for full schematics to the Pi 4B. All I am finding is the 4B reduced schematics and then Compute Module full schematics that are Revision 3 and thus use a different processor.

Thanks in advance!

Scott

[jamesh]

The full schematics have never been released, and are unlikely to be released.

[cleverca22]

what about adding certain parts back in, without releasing the entire thing

having things like the SPI chips visible in the schematics would help with users that want to write-protect it or are having trouble flashing things the official way

what about test-points for basic things, like usb or power rails or the uSD socket (if it has any)?

i can see how adding them back in may be too much work, but what about just deleting less when the CM4 reduced schematic is being done up?

[shuhn]

How are we to accurately interface with the Pi board if we do not know where things get connected to the processor? A simple example are the two signals leading into U5 of the A/V portion of the Pi 4. What exactly are they, what are they connected to and how do they work? Because I doubt they are PWMs and the MOSI/MISO part is just plain confusing.

And you supply schematics for the compute module, so why not the Pi? I am confused.

[cleverca22]

How are we to accurately interface with the Pi board if we do not know where things get connected to the processor? A simple example are the two signals leading into U5 of the A/V portion of the Pi 4. What exactly are they, what are they connected to and how do they work? Because I doubt they are PWMs and the MOSI/MISO part is just plain confusing.

And you supply schematics for the compute module, so why not the Pi? I am confused.

https://elinux.org/RPi_BCM2711_GPIOs

the "analog" audio is coming from gpio pins 40/41

if those pins are set to ALT0, they map to the hardware PWM controller, and the GPU firmware will update the duty-cycle constantly, the low-pass filter then turns it into analog audio

but if those pins are set to ALT4, they truely are MISO/MOSI, and they allow access to the rpi4 eeprom, where the boot firmware is held (technically, the PWM is always on MISO/MOSI, but chip-select isnt active)

https://github.com/raspberrypi/rpi-eepr ... #L199-L219

the calls to vcmailbox here, are to cut power to U5, so you dont wind up hearing the SPI traffic on your speakers as it re-programs the chip

it would be a lot more obvious and not require digging thru 3 different documents, if the SPI chip was simply on the schematic

[W. H. Heydt]

How are we to accurately interface with the Pi board if we do not know where things get connected to the processor? A simple example are the two signals leading into U5 of the A/V portion of the Pi 4. What exactly are they, what are they connected to and how do they work? Because I doubt they are PWMs and the MOSI/MISO part is just plain confusing.

And you supply schematics for the compute module, so why not the Pi? I am confused.

There is a lot less to a Compute Module than there is to a Pi. And--FYI--there should be a CM4 relatively soon.