Hi TJF, Now that is really interesting. I was just thinking about using the PRU's for the job.
In the end I gave up and connected an mbed microcontroller and did the job. However, that revealed an issue that could be the clue as to why I could not get the 1 wire to work with the BBB. I interfaced the mbed to the BBB via uart 1. At first I wired it up fairly directly. I got nothing -- even though I could get the BBB usarts to talk to each other. An oscilloscope revevealed that while the mbed's tx was connected to the bbb's rx, the voltage never went low enough to register the signal (pullup resister too strong?). So I put an optocoupler in line -- and it works perfectly. Now, in my ignorance, I'm wondering if I should try an optocoupler between the ds18b20 and the BBB. What do you think? Maybe I don't need the mbed after all. Kind regards Matt On Wednesday, April 6, 2016 at 5:45:51 PM UTC+10, TJF wrote: > > Hi Matt! > > A year ago I started with those sensors and I didn't have trouble to > connect them by the w1 kernel driver. But I don't remember what I did that > time, because I dropped that solution. The kernel driver doesn't support > broadcast messages and the sensors are triggered one after the other. I use > eight sensors to control a solar system and there's more than five seconds > between the first and the last measurement. Too much for my appliction. > > That's why I made my own W1-PRU driver using a GPIO pin (no additional > hardware). Now all sensors get triggered by a broadcast message, the > measurements are at the same time and values are available in less than a > second, which increases the speed of my controller loop. For development I > implemented a feature that logs the state of the data line at 1 MHz. Those > data may help you to understand what's going on on the bus. > > Unfortunately I didn't find time to document and publish the project jet. > The driver is based on libpruio (for pinmuxing). If you're interested let > me know where to send that (undocumented) code (FreeBASIC & PRU-ASM). > > BR > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/05add607-d720-4787-9e90-91f936b29961%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
