Exploring more interface ideas
T Chap
Posts: 4,223
These ideas aren't not ready yet, but are just some general concepts of bi directional level shifting that need tweaking to make one actually work. Ideally I'd like to find a method that uses at least 4 gates per package, and using diode packages as well (if needed) to avoid handlig small mono parts.
The XOR is close IF the 4070 cmos can handle 5v in while the VDD is 3.3. The lower XOR gate could really be dropped since the Prop's 3.3 may adequately turn on whatever you are sending it to in the 5v logic rhelm. I like the XOR method as it "could" possibly create a way where a conflict on each side can't pass through the gates to cause damage.
The 4050 idea clearly doesn't work, but is a great concept for level shifting, as they are designed to handle higher input voltages than the rail. They easily down shift and up shift. Some thought needs to go into this make it work while still keeping the parts count low per i/o.
The opto is great for isolation. It clearly works very well for downshifting(depending on your speed). You can get 4 per 16pin ic, so 8 dips or soics will get you interfaced effortlessly with 3$ worth of socketed parts. Upshifting is just as easy, but would require some diode gating, or maybe just as easliy some other logic gating taking up the same space as a diode pack.
I read the sticky but I think some further exploration is not a bad thing.
The XOR is close IF the 4070 cmos can handle 5v in while the VDD is 3.3. The lower XOR gate could really be dropped since the Prop's 3.3 may adequately turn on whatever you are sending it to in the 5v logic rhelm. I like the XOR method as it "could" possibly create a way where a conflict on each side can't pass through the gates to cause damage.
The 4050 idea clearly doesn't work, but is a great concept for level shifting, as they are designed to handle higher input voltages than the rail. They easily down shift and up shift. Some thought needs to go into this make it work while still keeping the parts count low per i/o.
The opto is great for isolation. It clearly works very well for downshifting(depending on your speed). You can get 4 per 16pin ic, so 8 dips or soics will get you interfaced effortlessly with 3$ worth of socketed parts. Upshifting is just as easy, but would require some diode gating, or maybe just as easliy some other logic gating taking up the same space as a diode pack.
I read the sticky but I think some further exploration is not a bad thing.
485 x 513 - 25K
Comments
Here is the input interface I am currently useing for my propeller project.
Link http://forums.parallax.com/showthread.php?p=595303
Rob7