Date: Wed, 13 Jul 2022 18:19:57 -0500 From: Jedi Tek'Unum <freebsd-arm-list-2022-fea3@qoruscant.com> To: "Dr. Rolf Jansen" <freebsd-rj@cyclaero.com> Cc: freebsd-arm@freebsd.org Subject: Re: Startup-/Shutdown Button for the Raspberry Pi 4 Message-ID: <165775440275.8.4265153478134935826.51718197@qoruscant.com> In-Reply-To: <E1F8EA20-D709-45FD-941F-DB28921601D1@cyclaero.com> References: <E1F8EA20-D709-45FD-941F-DB28921601D1@cyclaero.com>
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> On Jul 12, 2022, at 8:17 PM, Dr. Rolf Jansen - freebsd-rj at cyclaero.com= <nxtzmchnyjrirskcrisaafakxcekosgmhdcricnnjyxomsvwpn@simplelogin.co> wrote: >=20 > =EF=BB=BFOne week ago I started with exploring the Raspberry Pi 4 B, whic= h might be a substitute for the aging BeagleBone Blacks for my future proje= cts. >=20 > I very much like the built-in power button facility of the BBB, and unfor= tunately the RPi 4 has nothing comparable - the one button to rule it all. >=20 > I read a lot of howtos and blog posts (mostly for Linux) and nothing was = really worth to give it even a try, compared to live without the button. We= ll, this is not becoming an elaborated question, but here I am going to ela= borate my solution for FreeBSD. >=20 > 1. I Prepared a momentary push button for connecting it to the RPi: > ___=20 > | / > |/ > / > / > +-o o--------+ > | | | > | [R] 100 =CE=A9 | > | | | > o o o > Pin 5 Pin 6 Pin 13 > (SCL 1) (GND) (GPIO 27) Ok, I=E2=80=99ll bite. I=E2=80=99m not understanding this. I imagine that the resistor is a current limit for the gpio pin and not the= pullup. Regardless of how it is wired, why use SCL1 which is pulsing? And how can a= ny of this cause a boot? Is this =E2=80=9Cmagic=E2=80=9D dependent on some quirk(s) of RPi? Will it = work with others, like Rock64? > 2. I created a shutdown daemon in C for FreeBSD, lurking for push button > events on a GPIO port: https://github.com/cyclaero/shutdd >=20 > clang -g0 -O3 -fsigned-char -Wno-empty-body -Wno-parentheses shutdd.c -= lgpio -s -o /usr/local/bin/shutdd >=20 > shutdd [-p file] [-f] [-n] [-b] [-g] [-h] =20 > -p file the path to the pid file [default: /var/run/shutdd.pid] =20 > -f foreground mode, don't fork off as a daemon. =20 > -n no console, don't fork off as a daemon. =20 > -b GPIO bank id [default: 0]. =20 > -g GPIO line id [default: 27]. =20 > -h shows these usage instructions. =20 >=20 > echo "/usr/local/bin/shutdd" >> /etc/rc.local=20 >=20 > Restart and ready for testing the RPi's Power Button. >=20 > shutdd does not poll the state of the GPIO port, but instead utilizes Fre= eBSD's user space interface for GPIO interrupts for lurking on state change= s of the GPIO line - default GPIO.0.27. Therefore, no significant load is i= mposed on the CPU's. >=20 > After 2 hs of operation, in output of ps -ax: > ... > 550 - Is 0:00.03 /usr/local/bin/shutdd > ... >=20 > - No CPU load !!! >=20 > - Pressing the power button does the same as shutdown -p now >=20 > - Pressing the power button when the RPi is down but still connected to t= he 5 V power supply lets it starting up. >=20 > BTW, I left the RTC DS3231 on I2C 1. That means, the RTC and the power bu= tton share the same pins for SCL 1 and GND. >=20 >=20 >=20
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