From: tnp@invalid.invalid   
      
   On 06/05/2025 14:36, Theo wrote:   
   > The Natural Philosopher  wrote:   
   >> On 06/05/2025 14:19, Theo wrote:   
   >>> Andy Burns  wrote:   
   >>>> the BusPirate folks had issues with their BP5XL boards and needed to   
   >>>> junk a batch, I see that redesigned as the BP6 it's now on sale ...   
   >>>   
   >>> Yes, that's the kind of application where it's a problem.  You attach GPIOs   
   >>> to random stuff and intend to probe what's there.  That means you flip   
   >>> through the internal settings for input/output/pullup/pulldown and listen   
   >>> out to how the input changes.   
   >>>   
   >>> The leakage affects that kind of application badly (input pins should be   
   >>> high impedance but they aren't here) but if you are putting the chip in a   
   >>> board where you already know what's on the other end of the pin, you can   
   >>> design the circuit appropriately.   
   >>>   
   >>> RPis are more likely to be used in situations where you take the MCU and   
   >>> plug in and out random things onto the pins which are affected by it,   
   >>> compared with other MCUs where they only ever get put on vendor PCBs where   
   >>> everything is predetermined in the schematic.  So it's really a hobbyist   
   >>> focused problem rather than a wider problem.   
   >>>   
   >>> Theo   
   >> All my Pis end up on my design of PCB where stuff is either disabled or   
   >> its strictly controlled   
   >>   
   >> I cant see why anyone would enable an input pin and leave it floating.   
   >> Its simply bad design   
   >   
   > If you're making a logic analyser, that's what you do.  That's effectively   
   > what the Bus Pirate is.  (It will also generate some of the protocols it   
   > analyses, but that's a different feature)   
   NO. given that the logic analyser would most likely want to be 5V you   
   would have the inputs pulled down externally with a resistor in series.   
   >   
   > Anyhow they didn't leave the pins floating - they enabled the onboard   
   > pulldown resistor.  The problem is that the pulldown has unexpected side   
   > effects.   
   >   
      
   AFAIAC as a electronic engineer anything that isnt exnternally connected   
   is 'floating'   
      
      
   > Theo   
      
   --   
   There is something fascinating about science. One gets such wholesale   
   returns of conjecture out of such a trifling investment of fact.   
      
   Mark Twain   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)