i'm trying to program my raspberry 2 as a usb slave.
(like some other people on the net, but nobody seems to have succed yet ...)
I need to handle the full usb protocol negociation => create the descriptors myself !
I've read many things about USB protocol, etc ...
So here is what i know :
The pi itself can't be used as a slave, because of the hardware (usb ports are connected to a hub, forcing host mode)
=> there is a usb OTG port (the mini usb port in fact) : pins not connected to anything and could be used, but that would neeed hardware modification on the board itself, so ... not a solution for me.
So usb on itself is dead, but the pi has serials interfaces (I2C and UART at least).
I was thinking about connecting one of these to a "magical external chip" (here is the trick) that would simply convert serial to usb
=> many chips do that (TTL cable for example), but theses handle the USB protocol themselfs (needs driver on windows, etc ...)
=> not what i need.
What i need is something like teensy (see there : https://www.pjrc.com/teensy/) : it can be used to create usb peripherical and let the user program the full usb protocol himself. That's perfect, but i'd like to programm the full stuff on the raspberry.
I may have understood that Teensy does have a serial port too, so i could maybe do something like
Pi <= Serial => Teensy <= USB => ...
But i'm looking for something simpler.
I say it again : i need a simple bridge between UART & USB : no intelligence : receive from one side, transmit to the other. that's all.
I may have found these that could maybe do the stuff, for what i understood :
http://www.microchip.com/wwwproducts/De ... e=en533924
http://www.st.com/web/catalog/sense_pow ... 4/PF122777
But I'm not sure that's what I need ...
Someone know about a good chip / card to do my stuff ?
Note that i'm experienced in computer programming, so kernel stuff and drivers are not a problem.
sorry for the many grammar mistakes i may/must have done : french guy talking ! Feel free to correct them.