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It's a well-written, in-depth article about a very technical topic that affects a lot of us daily, but few of us are aware of its implementation details. Speci
by niftich 10y ago
It's a well-written, in-depth article about a very technical topic that affects a lot of us daily, but few of us are aware of its implementation details.
Specifically, there is a fascinating section about how to actually charge a phone with a dead battery; there is nasty catch-22 where you have to boot up the OS to negotiate the amount of current you want to draw, but since your batteries are dead and the default un-negotiated current isn't enough to boot, you have to get creative.
- Piskvorrr 10y agoMy old Xperias were capable to "boot" into a minimal bootloader (just enough to negotiate USB power, charge battery, and light the charging LED) and refused to boot further. I now see how it was done; great article.
- derefr 10y agoI'm confused as to why we haven't cut all this mess out by standardizing a dedicated microcontroller in the charging path, that handles AC/battery switching, battery recharging and discharging, etc. without getting the CPU involved. As if you could boot an AT computer so only its southbridge and BIOS were active, without the CPU coming up. I think recent Apple machines—e.g. the retina Macbooks—might have something like this, given the "Power Nap" feature and the fact that plugging them into power temporarily flashes a charging indicator on the screen even if the computer is "off." But it might really just be that the computer is never really "off" but just in a really deep CPU sleep-state. The test would be to kill the battery of one flat-dead, and then see if the charging indicator still appears on AC-in.
- niftich 10y agoI don't know for sure, but I'm hypothesizing that Qualcomm's Quick Charge actually works this way, as the presence of their hardware/firmware/secret sauce is required in both the charger and the device end to negotiate the upped voltage.