Harald, Am 02.12.2014 um 20:49 schrieb Harald Geyer: >> Yeah, if the sensor starts transmitting data before we've setup >> the IRQ we'll lose edges. > > Yes, but you missunderstood me. That's not the point. > > The point is that now the edges that the driver generates while > the gpio is configured as output are part of the preamble of the > data transmission. I think with your patch applied this is no longer > the case (we don't get interrupts for these edges anymore). So the > decoding needs to be changed to work with a shorter preamble. Hmm, I get always 84 edges. This value makes sense to me, 40 bits (80 edges) plus 4 preamble edges. >> But AFAICT the DHT is much slower than we are with setting up the IRQ. >> The DHT is a rather stupid device so we cannot use proper interrupting. >> But I can think of adding also polling support to the driver. >> Such that one can select whether she wants to use IRQ or polling... > > I don't like the idea of a polling driver. Also I don't think it will > be necessary. Of course polling is ugly, if IRQ works let's keep it as is. :) >>> Since it seems you have some interesst in working on these parts, >>> let me mention an unrelated issue: The DHT22 stops sending data >>> after a random time (think of days here) which AFAIK only can be >>> worked around by power-cycling the sensor. I mean to add something >>> for this to the driver but couln't make up my mind about what the >>> proper ABI for this would be, so right now I'm using some userspace >>> hack for this. (The issue was already discussed on the linux-iio >>> mailing list a few month ago, if you want to look into this. >>> Anyway: You have been warned ... ;) >> >> Oh, that's a very valuable information! >> Currently I'm evaluating some sensors for a private project. >> You can recommend a better temp/humidity sensor? > > No really. When I noticed these cheap little parts are actually > *cheap* parts, I looked which sensors are already supported by > hwmon, but none appealed to me, so I decided to try and work > around this in software as far as possible. It's not hard to do, just > hard to do right. ;) > > The best I can recommend you is to have a look at the list of > humidity sensors supported by hwmon yourself. Ok! Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
