4 ms·

such things exist (such as the pico from http://pimodules.com/ http://pimodules.com/) but I've had nothing but grief from its firmware using v1 and v2. There ap

by shabble 10y ago

such things exist (such as the pico from http://pimodules.com/ http://pimodules.com/) but I've had nothing but grief from its firmware using v1 and v2. There appears to be a new version, and I suppose it might be better now. For most <1 day outages, a simple USB power-bank with passthrough capability (output whilst also possibly charging) will happily keep the pi going, but without some frankenbodging there's no 'power lost' signal that the pi can sense. I've idly toyed with the idea of a phototransistor on the powerbank status LED and an attiny or something. Now that I think about it, there was someone trying to make a supercap idea, but I don't think it went anywhere: https://www.indiegogo.com/projects/juice4halt-supercapacitor-ups-for-raspberry-pi#/ https://www.indiegogo.com/projects/juice4halt-supercapacitor...

mountaineer22 10y ago
Could you not simply have a 5V DC power adapter on the same mains line, and detect if it is on or off via one of the GPIO pins? Is that considered frankenbodging?
- analog31 10y ago
  That's what I would do. The loss of 5 V on the GPIO pin triggers a interrupt, which forces a graceful shutdown. As I understand it, there's a command which halts disk access, which is mainly what's needed for a graceful shutdown.
  - washadjeffmad 10y ago
    You can use "systemctl poweroff", /sbin/shutdown, "shutdown -Ph now" (in case of wonky ACPI), and a few others to gracefully halt. You can also echo a magic sysrq key (eg-"b") to /proc/sysrq-trigger. "e i s u o" would do the full graceful shutdown. This nicely asks processes to quit, kills (almost) everything, halts the system, syncs disks, and remounts fs ro before going down. Or you could create a service with systemd to (run a script to) check when dbus gets a particular signal, like a network device being added or removed if an SSID disappearing was your indicator of power loss, then halt. I'd probably just plug them into a UPS, though. Just have it send one of the shutdowns to the "master" when running battery power for longer than a few minutes.

by shabble 10y ago

mountaineer22 10y ago

Could you not simply have a 5V DC power adapter on the same mains line, and detect if it is on or off via one of the GPIO pins? Is that considered frankenbodging?

analog31 10y ago
That's what I would do. The loss of 5 V on the GPIO pin triggers a interrupt, which forces a graceful shutdown. As I understand it, there's a command which halts disk access, which is mainly what's needed for a graceful shutdown.
- washadjeffmad 10y ago
  You can use "systemctl poweroff", /sbin/shutdown, "shutdown -Ph now" (in case of wonky ACPI), and a few others to gracefully halt. You can also echo a magic sysrq key (eg-"b") to /proc/sysrq-trigger. "e i s u o" would do the full graceful shutdown. This nicely asks processes to quit, kills (almost) everything, halts the system, syncs disks, and remounts fs ro before going down. Or you could create a service with systemd to (run a script to) check when dbus gets a particular signal, like a network device being added or removed if an SSID disappearing was your indicator of power loss, then halt. I'd probably just plug them into a UPS, though. Just have it send one of the shutdowns to the "master" when running battery power for longer than a few minutes.