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   REPLY: <9qjq7k-sk32.ln1@esprimo.zbmc.eu> 29fa7b6c   
   PID: SoupGate-Win32 v1.05   
   On 19/01/2024 16:15, Chris Green wrote:   
   > When you power down a Pi is there any simple way to protect inputs   
   > which are being driven by externally powered equipment?   
   >   
   > I have A2D devices on the I2C bus which are powered from the Pi, if   
   > the Pi has power removed the A2D's will be unhappy I think as their   
   > inputs will still have the voltages they are measuring applied to   
   > them.   
      
   ??? If they are powered from the pi, how can they still have voltage?   
   ?? if they are on the I2C bus, how are they connected to the A2D inputs   
   on the Pi?   
   >   
   > Similarly I may have one or two logic inputs which are driven by   
   > external signals (to see if things are turned on for example) and   
   > these inputs will still be there (at 3.3v logic levels) when the Pi is   
   > powered down.   
   >   
   > Would diode clamps to the Pi's 3.3v supply be OK or are there better   
   > ways?   
   >   
      
   I suspect those already exist internally.   
   It is more relevant to prevent those getting smacked with high current.   
      
   a small resistor would limit any current   
      
      
      
      
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   The greener grows the grass.   
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