In other words, after a cold boot the pull is always up. And if I disable the pullup from userland, and issue a sudo reboot command, the pull stays in the last state (as expected) until the next cold boot.Īnother piece of information is that I am unable to change the deafult pull state to down as well as off. Some more information: I read in the BCM2835 ARM peripherals datasheet (page 100, GPIO Pull-up/down register GPPUD) that "the pullups are maintained even in power-down mode when the core is off, when all register content is lost". I have unsuccesfully tried changing the default pullup resistor state of GPIO17 by following the dt-blob method described at the following link.Ĭould you please let me know if the article above is still current and if there is any diagnostic messaging that can be enabled to allow troubleshooting this. The board runs raspbian and raspberrypi-bootloader version 1.20150923-1 straight out of the repository. The 50-60 kOhm internal pullup is enough to drive more than 3 times the allowed leakage current.Īfter driving the pin with more than 10 uA for the first time, the Pi must contine toggling it faster than 10 Hz to prevent the watchdog circuit from triggering an alarm, leaving no time to boot and start a toggling process from userspace. The pin must float, with no more than 10 uA leakage current, until it first drives the watchdog. In particular, I need to disable the pullup on GPIO17 which is connected to a hardware watchdog circuit in my application. I am perfectly able to control all the pin pullups and pulldowns from userspace (I have verified all with an oscilloscope) however this does not help me. I am evaluating the use a Raspberry Pi Model B+ v1.2 board in an industrial control system.
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