From: jpsa@cantab.net   
      
   In article , news@druck.org.uk says...   
   >   
   > After getting another Pi 5, I've moved a Pi 4B running Bookworm in to   
   > the role taken by a Pi 3B running Bullseye, which is monitoring 6   
   > ds18b20 sensors, configured as 2 1-wire buses with 3 sensors on each.   
   >   
   > With the Pi 3B, I could either read the sensors sequentially taking   
   > about 0.9s each, or using threads simultaneously in 1.0s. The Pi 4B with   
   > Bookworm reads the sensors sequentially a shade faster at just over   
   > 0.8s, but when reading simultaneously, returns 2 after 0.8s, another 2   
   > after 1.6s and the last two at 2.4s.   
   >   
   > Anyone have an explanation for this?   
      
   No, but AIUI the "right" way to do this is to send the text "trigger" to   
   /sys/bus/w1/devices/w1_bus_master1/therm_bulk_read before reading the   
   values as normal. The trigger causes them all to start a conversion at   
   once, following which the reads all complete immediately once a single   
   conversion time has elapsed.   
      
   As a quick hack, try executing the following before reading your   
   sensors...   
      
   sudo su < /sys/bus/w1/devices/w1_bus_master1/therm_bulk_read   
   EOF   
      
   --   
   John   
      
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