comp.arch.embedded erratic behavior with a Rohm DA converter
A Rohm BU2507, a six channel da converter, is used for setting bias points and gain for several op amps. The settings for each dac are transmitted by a microcontroller. Rohm's converter works very well... most of the time. Occassionaly, though, the output will be 0 volts instead of what is expected. A conceivable cause could be a time out action taken by Rohm's device when a data transmission is interupted by an interupt within the microcontroller. This is pure guessing, however. Is anyone familiar with this device seen such trouble? If so, do leave a message here if you have any suggestions.
I can't speak for any one else, but the reason I haven't answered this is _not_ because I need to see a post a bazillion times before I respond to it. Rather, it's because I know nothing specific about Rohm parts.
If you _do_ feel like the fifth time is a charm, try a different title, like "Can't get DAC to work, need suggestions".
In the mean time, a general suggestion for this sort of thing (if the 'sometimes' is often enough, which is hard to tell because you haven't said whether it's seconds or years in between events) is to hook up a two- channel digital scope to the thing: one on the output, and one on the data input. Then trigger the scope on the output going to zero. Digital scopes will capture what happened before the trigger, so you'll get a chance to see what was going on before the bad things, and this will help to guide you. Obviously, more channels are better, as you can capture data, enable, and clock all three.
If you suspect that an interrupt is causing a problem then _I_ suspect that you are (a) bit-banging the interface, and (b) don't have your priorities set up right. But since you haven't said what environment your software is running in -- whether Linux, no OS, an RTOS (and which one), etc. -- I can't comment on what you may be able to do to alleviate this problem. Similarly, since you haven't said what else you're doing, I have no basis for knowing if anything that'll alleviate the problem won't screw up something else.
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