On Wednesday 20 July 2005 01:09 am, Matthew Percival wrote: > G'Day, > > I am currently trying to weed out why I still cannot read from my > DS2431 device, and in my testing I stumbled across a minor bug in > BUS_send_data(). > > When I `cat 2D.serial/memory', it does not work, so I checked `cat > statistics/errors/BUS_*' and noticed that BUS_send_data_errors was 1, > however, when I checked `cat statistics/errors/OMAP_*', everything was > 0! The only logical explanation is that the error being generated by > BUS_send_data() was not due to OMAP_sendback_data() returning a non-zero > value, rather that memcmp() was coming back non-zero. When I checked > the code for this section, I noticed a small mistake. > > The line is as follows: > (ret=BUS_sendback_data( data, resp, len,pn )) || > ((ret=memcmp(data, resp, (size_t) len))?-EPROTO:0) ; > Which, if I assume BUS_sendback_data() is returning `0' and memcmp is > returning `unknown', evaluates to: > 0 || (unknown ? -EPROTO : 0) > In other words, that *line* evaluates to either 0 or -EPROTO, but the > value or ret will be the value of unknown. You can fix this by moving > the bracket like so: > (ret = BUS_sendback_data( data, resp, len,pn )) || > ((ret = memcmp(data, resp, (size_t) len) ? -EPROTO : 0)); > Now, if memcmp returns a non-zero value, ret will equal -EPROTO. > You're right. Fixed, and clearer too. > I have also noticed that owfs seems to fall asleep on me at times: > sometimes when I give a command (ls, cat, etc), it will just hang on > that. If I background the ls/cat and `killall owfs' it will finally act > on the command (with a predictable `No such file or directory' error). > I have tried disabling multithreading, but that did not seem to be the > problem. Has anyone else experienced anything like this before? > > As to the specifics of the function called when catting > 2D.serial/memory/, perhaps it is just my misunderstanding, but it seems > to me like calling BUS_send_data() is not the best thing to do. > BUS_send_data(x,3,y) sends three bits, then reads three bits and > compares them. If I am correctly understanding the way this device > works, are the bits you read back there not the contents of the memory? > I could very well be wrong here, as I am finding the documentation for > the device a little hard to follow at times, but that is just how it > seems to me: I need to send 0xF0, some sort of reference address, then > start reading back data stored in that address. > Never properly documented, but: BUS_send_data sends and compares data (the "data" is specific to DS2480B/DS9097U syntax that uses in-band commands to the adapter, hence "data" and "command" modes). BUS_sendback_data sends data and returns what it reads. BUS_readin_data sends dummy data and returns what it reads.
Clearly these are all slight variations of the underlying "send bits and look at what the bus does to them", but that's the essence of 1-wire communication. Tell me specifically where you are looking, please. > -- Matthew > > > > ------------------------------------------------------- > SF.Net email is sponsored by: Discover Easy Linux Migration Strategies > from IBM. Find simple to follow Roadmaps, straightforward articles, > informative Webcasts and more! Get everything you need to get up to > speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
