Low power USB host solution

[houtouridis]

Posted on March 30, 2013 at 12:43

Hi all,

I'm using STM32F100 processors for a while now and i had no issue so far. I'm looking for a solution that provides USB host functionality to a Flash disk but it must  be powered by battery, so it must by energy efficient. I'm new to USB(first project) so correct me if I am ''from out of space'' here. Now. The data transfer will be very very small and I plan to keep USB disabled for most of the time. Only 5-6 writes and reads per day. And the file-sizes will be 2-3 Kb. I found stm32L151-2 cpu and it is pretty good actually. It fits all my other requirements, but I believe it provides only USB device functionality, no USB host. Is there any way to run a usb host library (even if it is from a 3rd party) in that cpu? If not what is the most energy efficient ST Cortex-m3 cpu for usb host? The usb speed is not important. I wander if it is possible to use an external USB host controller with the libraries provided by ST or its partners. And how easy is that? I use my own OS(preemptive multitasking kernel for Cortex-M3/M4) and my Fat32 library and I had no issue with that so far. I dont know if it is problem now. Regards, Christos Houtouridis #low-power #usb #host

[Tesla DeLorean]

Posted on March 30, 2013 at 13:54

While you're walking around, consider if removable storage like an SD Card might be a more appropriate solution.

[houtouridis]

Posted on March 30, 2013 at 15:57

[Tesla DeLorean]

Posted on March 30, 2013 at 16:58

And second, I believe SD consume even more power than usb. A SD consumption is around 80-100mA@25Mhz, 170-200mA@50Mhz while a typical USB drive consumes only 70-90mA when a file is transfered and around 40mA idle.

The problem, as you stated was with being a USB Host, I'm not aware of a solution to that. I think you might want to look at the power numbers more carefully. USB is a 5V interface, MSC peripherals can draw 500mA, presuming you can't control what's plugged into the socket. And power being a function of voltage and current. I'm some what sceptical that the power required to run the same type of flash devices natively at 2.7 or 2.8V is somehow less efficient than having a USB device with similar technology and voltage regulators, and 48 MHz crystals, and 480 Mbps support.