From looking at the Xavier carrier board design file schematic and the carrier board specification document, GPIO pins such as board pins 22 and 15 should have 1Mohm pull-down resistors. Yet when using the Jetson.GPIO library they seem to behave as if they don’t have such resistors, and when I measure the resistance between one of those pins and ground I see no connection at all.
What am I missing here? How do I use GPIOs with internal pull-down resistors?
Can you expand on that? I don’t understand what you are suggesting I do to fix the problem.
I’ve already looked at the pinmux spreadsheet, but it also says that the pin has a pull-down resistor (I assume the configuration shown in the spreadsheet is the default one for the Xavier). Are you saying I should be changing the configuration?
please modify the pinmux spreadsheet, customize the content below “Filled in by Customers” column.
once you finish the modification, you’ll need to click the [Generate DT file] to output new gpio and pinmux device tree files, please also check [Jetson AGX Xavier MB1 Platform Configuration chapter] for the steps to create the cfg file.
you’ll need to re-flash the board with the new cfg files to make the change.
thanks
I don’t want to change the device tree configuration: I want to understand the default configuration. Why do the data sheets appear to incorrectly report the default pin configuration, and where can I find correct information?
I understand that you’re trying to answer my question but you aren’t giving the relevant information. Specifically, what document and page should I look at to identify whether a particular pin has a pull-up or pull-down resistor? Please show me the document and page. I don’t want to be crawling through config files.
Checking the live configuration on a particular Jetson might happen to work, but the behavior should be documented without having to boot up and connect to the device. The design files are a ZIP folder of dozens of documents, and I haven’t been able to find one which aligns with the apparent behavior of the board.
Yes. GPIO17 (pin 22 on the main GPIO header) is listed as having a 100k pull-down resistor in the spreadsheet, but it doesn’t behave like it has a pull-down resistor in practice when I tested it.