#35 OWHTTPD does only detect DS24B33 40% of the time

[Anonymous]

I have a setup with an DS9490R and a DS24B33 over 2m cable. Detection of the Chip with the ow-filesystem works fine. In uncached mode I can see with "while true; do ls -l /mnt/owfs/unchached/; sleep 0.1; done" changes in nearly real-time. The chance the device does not appear is near 0.

But in the httpd view under localhost:2121 there is a chance of 50-70% when I press F5 that only the DS9490 appears. The connected DS24B33 does not appear at all in this case or it does appear with corrupted data or even with an wrong ID.

[Jan Kandziora]

Do you use owfs and owhttpd at the same time?

If yes, you are likely doing it wrong, running both directly on the same USB host adapter by specifying the -u (or --usb) option, or in the config file. This "works a bit" because libusb allows alternating access from multiple programs for single USB transactions. However, it does not work reliably for owfs as the access, especially scanning the bus, needs multiple USB transactions for one onewire transaction. When a second program accesses the host adapter during an unfinished onewire transaction, that one breaks. Hence the broken listing.

When you want to use more than OWFS one program accessing the same host adapter, you have to configure owserver as the sole access gateway to USB. It's easy, stop all the OWFS programs and start owserver -u. Then advise all the other programs to use the owserver by starting them with -s localhost:4304 instead of -u.

That way, the concurrent onewire transactions from the other OWFS programs are serialized by owserver and all is fine.