Hack to make pi USB jacks more powerful
Posted: Thu Nov 26, 2015 4:57 pm
While not software, exactly, I wanted to put an always-on pi on my network (well, another one), in order to have a big shared space. For that, of course you don't use the SD card unless you want to be replacing them, and big USB sticks aren't all that cheap - or as big as I want.
Knowing my old "thai vibrator" (no disrespect to the Milwaukee one) laptop spinner would use too much power, I bit the bullet and got a $amsung 850 evo pro 500gb drive for that. And, even that wouldn't power up off the pi's USB, even with the magic undocumented edit to /boot/config.txt. I suspect the power draw measurements in the review I saw were only for post-boot, not peak inrush during setup.
I found this:
http://hackaday.com/2015/04/06/more-pow ... usb-ports/
Which is a hardware hack that actually maxes out the USB power supply at something around 2 amps. Even an SSD seems to draw a little extra at boot time.
This works! It will even do the older spinner drive (though my power supply does get warmer). It was kind of interesting to change that resistor as I only had 0602 size in that value - I had to put the new one on edge and scrape a little solder mask off the groundplane to do it, but hey...it works.
I'm using one of those cheap National Semi "simple switchers" you can find on ebay from china, and a wall wart, I suspect Ada's 5.1v 2a wart/switcher would do as well - after all, it's still all coming through that little fuse. In my case this will be running off the same 12v/60ah UPS system that keeps the ham rig ready no matter what, so the simple switcher is a better choice, and it'll run even if the inverter shuts off for some reason...for awhile, anyway.
I'm tempted to just copy it all (offline on another machine) and mount this over / and skip any worry about SD cards wearing out - but at the very least I will partition it and mount it over /home and /var, which normally take the most beating. Then I can just use the /home/pi/Public directory as a share for the rest of the LAN.
I already have an Amped WAP with a share - but it's dog-slow. Evidently the little CPU in there can only do around 1 mbit/second in that mode...and even with the pi sharing virtually all IO over USB - this should do substantially better (it will be wired ethernet, but then, so is the WAP)...
Knowing my old "thai vibrator" (no disrespect to the Milwaukee one) laptop spinner would use too much power, I bit the bullet and got a $amsung 850 evo pro 500gb drive for that. And, even that wouldn't power up off the pi's USB, even with the magic undocumented edit to /boot/config.txt. I suspect the power draw measurements in the review I saw were only for post-boot, not peak inrush during setup.
I found this:
http://hackaday.com/2015/04/06/more-pow ... usb-ports/
Which is a hardware hack that actually maxes out the USB power supply at something around 2 amps. Even an SSD seems to draw a little extra at boot time.
This works! It will even do the older spinner drive (though my power supply does get warmer). It was kind of interesting to change that resistor as I only had 0602 size in that value - I had to put the new one on edge and scrape a little solder mask off the groundplane to do it, but hey...it works.
I'm using one of those cheap National Semi "simple switchers" you can find on ebay from china, and a wall wart, I suspect Ada's 5.1v 2a wart/switcher would do as well - after all, it's still all coming through that little fuse. In my case this will be running off the same 12v/60ah UPS system that keeps the ham rig ready no matter what, so the simple switcher is a better choice, and it'll run even if the inverter shuts off for some reason...for awhile, anyway.
I'm tempted to just copy it all (offline on another machine) and mount this over / and skip any worry about SD cards wearing out - but at the very least I will partition it and mount it over /home and /var, which normally take the most beating. Then I can just use the /home/pi/Public directory as a share for the rest of the LAN.
I already have an Amped WAP with a share - but it's dog-slow. Evidently the little CPU in there can only do around 1 mbit/second in that mode...and even with the pi sharing virtually all IO over USB - this should do substantially better (it will be wired ethernet, but then, so is the WAP)...