Hi,
is there a simple non-expansive method to electrically
protect the GPIOs from shortcuitry or slight overvoltage
(5V instead of 3.3V or 1.8V) with a simple <something>
between the CPU side of the GPIOs and for examples sensors
or similiar?
Best regards,
mcc
Common sense? Zener diodes? Inline resistors? Pull-ups? Opto-
couplers?
Andrew Bradford <andrew@bradfordembedded.com> [12-09-05 19:48]:
> is there a simple non-expansive method to electrically
> protect the GPIOs from shortcuitry or slight overvoltage
> (5V instead of 3.3V or 1.8V) with a simple <something>
> between the CPU side of the GPIOs and for examples sensors
> or similiar?Common sense? Zener diodes? Inline resistors? Pull-ups? Opto-
couplers?
Hi Andrew,
thank you for summarizing up my questions again. What /you/ choose
if you had a beaglebone and want to protect it from the errors,
all humans tend to make from time to time?
Thank you very much in advance for yor help!
Best regards,
mcc
level switchers, CPLDs, etc
Opto-couplers have fast switching times and have the distinct advantage of isolating the CPU from any spikes generated by nasty inductive loads, such as solenoids, motors, relays, etc. 
Cheers!
2012/9/5 Koen Kooi <koen@beagleboard.org>
You could add resistors and zeners, but that may not be that cheap. Zeners may not that accurate and you may have to pick one a little less than 3.3V.
You could add voltage dividers for those that are inputs, but it will not help on those pins used as outputs.
Gerald
I have attached an OSHW idea. It will be commercially available soon.
Regards,
Jordi Binefa
Al 05/09/12 19:36, En/na meino.cramer@gmx.de ha escrit:
set05_07.zip (155 KB)
Are you going to sell a cape? Or are you just trying to protect
yourself while prototyping?
If you're selling a cape, it depends on what kind of I/O you're doing
(for example, bidirectional and opto-couplers don't always work unless
you buy the expensive ones, plus they're kind of big). Zeners and tvs
diodes aren't always great, they're better for transient suppression of
things like ESD but can do this job, too.
I personally put some small resistors inline for over current
protection. Limit so that in case I drive an output high and the thing
on the other end drives the output low, current won't exceed 3mA or so.
1k is a nice value Just watch out for pull-ups/downs to make sure
your levels stay in the proper ranges (ie: high is still high and low is
still low).
Common sense for the voltage matching, or level shifters.
Other than that, buying more bones.
They're cheap, right?
-Andrew