GPIO current control

[seamusdemora]

I have read that limits may be programmed for the output current of GPIO pins. However, after reading several online versions of Broadcom's data sheet for the SoC, I've found nothing to corroborate the data in this reference. Is there a "definitive source" for this GPIO current limit function, either in hardware documentation OR software documentation?

[JamesH65]

That scribd document is correct. Not sure why it's not in the peripheral specification, or where that linked document originated though.

[lurch]

IIRC there were a bunch of additional mini-documents added to scribd by Gert. See also the "More From Anonymous I42Heqce7f" towards the bottom of that page. I think scribd itself has changed quite a bit since Gert was using it (e.g. you used to be able to download the PDFs without registering, which it seems you now can't do) so presumably Gert's old account has been deleted.

EDIT: And in fact https://github.com/raspberrypi/documentation/blob/master/hardware/raspberrypi/gpio/README.md does link to that scribd page.

[JamesH65]

Ah, thanks. We should probably pull all that stuff in to our docs somehow rather than relying on scribd.

[JamesH65]

This doc https://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/README.md shoud be updated to link to our own version of the scribd doc, or just insert the relevent bits in to the page itself.

[seamusdemora]

Sorry to be so slow following up. Thank you for responding, and making this crystal clear.

[seamusdemora]

@JamesH65 :

This doc https://www.raspberrypi.org/documentation/hardware/raspberrypi/gpio/README.md shoud be updated to link to our own version of the scribd doc, or just insert the relevent bits in to the page itself.

The document you referenced is valuable as a reference for the GPIO Electrical Characteristics (ref the "Voltage Specifications"). However, it must be noted that as it refers to the BCM2835, some of these specifications may be out-of-date.

This document also contains a statement that these Voltage Specifications "[were] extracted from the Compute Module datasheet here." Following this link proved useful in that the CM4 document contains related data (ref 3.3. Electrical Specification, pp 15-17.

However, in reviewing the CM4 document, two questions arise:

1. Does the CM4 document accurately represent the RPi 4B GPIO? REF the statement "The design of the CM4 is loosely based on the Raspberry Pi 4, Model B"

2. The current GPIO document contains numerous details that are not covered in the CM4 document - For example, Drive Strength. Can it be assumed that details covered in the current document for the BCM2835 still apply to the BCM2711?

[JamesH65]

1. yes
2. yes

[seamusdemora]

@JamesH65

Ah, thanks. We should probably pull all that stuff in to our docs somehow rather than relying on scribd.

That's still a great idea. :)

[aallan]

Ah, thanks. We should probably pull all that stuff in to our docs somehow rather than relying on scribd.

That's still a great idea. :)

There are no links from that page to scribd?