While practicing a talk the other night on my new Asus laptop, my Logitech remote presenter, which had worked fine a few hours earlier, suddenly became flaky. When I clicked the "next slide" button, sometimes there would be a delay of up to ten seconds; sometimes it never worked at all, and I had to click it again, whereupon the slide might advance once, twice, or not at all. Obviously not useful.
Realizing that I'd been plugged into AC earlier in the day, and now was running on battery, I plugged in the AC adaptor. And sure enough, the presenter worked fine, no delays or glitches. So battery was the issue.
What's different about running on batteries? I immediately suspected laptop-mode, which sets different power profiles to help laptops save battery life when unplugged.
The presenter acts as a USB keyboard, sending key events like PAGE DOWN, and on other distros (specifically Arch Linux) I've had problems with USB keyboard devices disappearing when laptop-mode is active.
So I moved /etc/init.d/laptop-mode out of the way to disable it, and rebooted. Tried the presenter again: no improvement.
But it was laptop-mode anyway. Apparently even though /etc/init.d/laptop-mode says in its header that its purpose is to start and stop laptop-mode, apparently laptop-mode starts even without that file. The key is the configuration file /etc/laptop-mode/conf.d/usb-autosuspend.conf, where I changed the line
In theory, I should have been able to do
service laptop-mode restart to test it,
but I didn't trust that since I'd just established that
/etc/init.d/laptop-mode didn't actually control laptop-mode.
So I rebooted.
And the presenter worked just fine!
I was able to give my talk that afternoon without plugging in the AC cord.
Ironically, this particular talk was on giving tech talks, and one of my points was that being prepared and practicing beforehand is critical to giving a good talk. I'm sure glad I did that extra practice run with the presenter and no power cord!
[ 16:13 Nov 03, 2013 More speaking | permalink to this entry | ]