Re: Reinventing the Shift Register with Comedi?

First of all, I've got no experience whatsoever in the thing you're 
trying to accomplish. So if the following sounds stupid, just ignore it! :D

If the internal clock can be sampled from the outside, you might be able 
to run a simple real-time RTAI program on 100 kHz, depending on the 
amount of oversampling you need to get the timing accurate enough. Than 
just sample the clock pulses with the input line of the serial/parallel 
port and if rising or falling, update the output line as needed.

Kind regards,
Arno.


David Smoot wrote:
> I've got a project and I think Comedi is the only tool short of a custom 
> board that might be able to pull it off.
> 
> I need to interface to some ancient (circa 1978) encryption gear.  I 
> need to be able to bit bang some configuration data into and out of this 
> box. 
> 
> The crypto unit produces a internal clock at 5kHz.  To configure the 
> unit I have to set an enable line high and then clock a 16 bit 
> configuration word in one bit at a time in sync with the clock.  
> According to the timing diagram I need to update my output line on the 
> rising clock edge.
> 
> Assuming all goes well with that, then I have to read a 24 bit response 
> back.  But the unit I am talking to updates its output on a rising clock 
> edge so I need to read the line on a faling clock edge.
> 
> Basically I see the problem as implementing a shift register in software 
> using Comedi but with the added twist of needing to drive off of either 
> a rising or falling clock edge.
> 
>  From reading the API documentation, this looks feasible to do what I 
> want.  But I do not see the API allowing falling edge triggering.
> 
> Do I need to invert the clock line to implement falling edge triggering 
> or am I missing something?
> 
> Does what I describe (using Comedi to implement a shift register) sound 
> feasible?  Has it been done?  I tried searching the archives with no luck.
> 
> Thanks for your time,
> David Smoot

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Received on 2006-08-08Z04:53:25