Re: [Emc-users] usb to parport adapter

[Stephen W. P. <sp...@so...>]

Kim Lux wrote:

>I wholeheartedly agree that inb and outb shouldn't be used to access the
>port.  Did we agree that *IF* we decided to access it this way that the
>virtual port would (software wise) act the same as the real port ?
>  
>
What I'm saying is that there *is* no virtual port.  Then, I go on to 
say that even if there were, it wouldn't work because of the 1ms USB 
packet rate.

So, I guess that either way, it's a no-go for direct port access.  It 
*might* work with something like Jon Elson's universal stepper 
controller, because that actually looks a lot more like a printer than a 
geckodrive (in terms of data transfer protocols).

>On Mon, 2004-11-29 at 16:34 -0500, Stephen Wille Padnos wrote:
>  
>
>>Kim Lux wrote:
>>    
>>
>>>btw: have we agreed that inb and outb should work with the <virtual> USB
>>>interface ?  Did we agree that at some level the USB interface looks
>>>like its hardware mapped I/O counterpart or is that wrong ? 
>>>      
>>>
As far as I know, that's the wrong part :)  I took a look at 
drivers/usb/uss720.c, which is a pretty generic USB<-> parallel driver.  
When you do a write to the device, it just makes a bulk data packet to 
be transmitted in the next USB frame.

(of course, it does look the same at the open / read / write / close 
level, but that's not too relevant to this discussion)
- Steve

(there is no spoon)