On 11/23/2016 3:15 PM, Warren Young wrote:
On Nov 23, 2016, at 3:40 PM, John R Pierce<pierce@xxxxxxxxxxxx> wrote:
On 11/23/2016 2:24 PM, Leon Fauster wrote:
DIY based onhttp://www.pcengines.ch/ hardware ...
...tis not suitable for USB power (5V, up to 2.5 amp)
I think you mean 2.5*watts* not amps. USB 2.0 and below are 500 mA @ 5 Vdc max == 2.5W. There are nonstandard extensions to USB to allow 2+ amps, but you can’t expect to get that from generic USB ports.
USB 2 battery charging extensions 1.2, from 2010, allow as much as 5
amps in charge mode, and 1.5 amps while communicating over the USB.
Yes, the port (or power adapter) has to be built to allow this much
power, and the device has to verify the port can provide it before it
can suck it down. my 5+ year old laptop has one such 'charging' port,
the other ports are limited to 0.5amp. you have to enable the charging
port in the BIOS, and it can be configured to stay live when the laptop
is sleeping as long as the laptop is plugged in and not running on the
laptop's internal battery.
http://www.usb.org/developers/docs/devclass_docs/BCv1.2_070312.zip
--
john r pierce, recycling bits in santa cruz
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