I have written several C programs which gather data over the parallel port up to 100 times per second. So I am kind of knowledgeable about ports, pins, signals etc.
BUT!, cannot figure out with my hrs of reading how to read/write to my devices ( over the USB because I haven't understood how to point to a specific device and what signals are necessary for the USB to carry signals to my AD chip.
My C programs have 8 repeats of about 10-11write commands (control/data) to the AD and 1 inb to the status byte. Hence, this would need to be done over USB. How does a device know when it is being addressed (the port id?). If via a port id how can I learn which port is connected to which device??
How fast can I rip data from a single device I understand there can be a 125ms delays on the USB line so am I limited to 8 commands/sec??
I am sure the USB does not want my device's 5 volts so what is done with the USB's 5 volt line? Do I need to ground my device circuit to the USB cable ground??
Is there a handshake which transpires for each access on the USB line?? I have been grinding on this stuff for several weeks and need some help here, THANKS.