Understanding the schematics

Hi, all. I am reading the Unmatched schematics. On page 2, the schematics show that PWM0 is connected to “Header Pins”.

For the life of me I can’t find these alleged header pins :)–my application is looking for 4 PWM pins. I suppose I’m not reading the schematic correctly–can someone help me understand which header pins (and bonus marks for which chip package pins) the PWM0 comparator lines are on? I have found the PWM1 pins.

I took a look at this just now.

I can only see that pwm0 controls two LEDs:

  1. D12 which on my board is flashing orange
  2. D2 which on my board is green, but according to the schematic is an RGB LED.

I can’t see any headers for PWM0 anywhere.


The board has gone through a number of revisions. I think the schematic hasn’t been completely updated after each revision. For instance, page 18 documents the FMC connector, which doesn’t exist on the production boards, but apparently did exist on early prototypes. It is at least marked DNP (do not place) on the schematic though. There is probably other stuff that hasn’t been properly updated.

There was supposed to be a board level hardware document produced, but that is the one document that is still missing from the SiFive Boards Unmatched web page.

Meanwhile, I would suggest the best sources of info are the u-boot and linux kernel sources. At least we know those are OK because the system does boot linux.

That’s the interpretation I was coming up with too, thank you for the confirmation.

Is there a place for me to point out issues like this one? (something like a GitHub issues?) This way, not only will maintainers have a list of issues to work against, others can quickly discover something is a known issue in the documentation.

I can file an internal doc issue pointing at a forum post. We don’t have anything better than that for consumer customers wanting to report doc issues.

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Ok, that works. Thanks, Jim, I appreciate the clarification!

I’m told that only PWM1_0 is on the headers.

Thank you, Jim.