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   On 2024-03-23, The Natural Philosopher  wrote:   
   > My choice tree  is between the GPIO out signal never being received by   
   > the ultrasonic module, or the GPIO in signal is being missed by the Pi   
   > PICO on account of possibly some interrupt masking its appearance until   
   > it is too late and its gone low again.   
      
   Or there never is a signal on the module output.  You should write your code   
   to cope with such problems - sample code/libraries often skips the error   
   handling, but that does not mean *you* can if you want reliable operation.   
      
   Hook up an oscilloscope or logic analyzer to check what is the case.  A   
   cheap 8-channel USB logic analyzer is a great tool to have around when   
   working bare metal:   
      
   https://www.aliexpress.com/item/1005005993277484.html   
      
   Using the Saleae software on these is *not* allowed by the license, but   
   sigrok/pulseview work great:   
      
   https://sigrok.org/   
      
   > We are running bare metal-ish here.   
   > Back in the day I would have used a chip emulator with hardware break   
   > points.   
   > And a cost of hundreds of thousands.   
      
   Nowadays, you would use a SWD debugger, since the debug/emulation logic is   
   already integrated in the RP2040!   
      
   Something like the JTAG Hat on a Raspberry PI:   
      
   https://www.schwingen.org/jtag-hat/   
      
   or any SWD probe supported by OpenOCD (FTDI, CMSIS-DAP work fine), like the   
   Raspberry Pi Debug Probe (which works for the RP2040, but lacks reset   
   signals and support for voltages other than 3.3V):   
      
   https://www.raspberrypi.com/documentation/microcontrollers/debug-probe.html   
      
   That sets you back about 20€, and gives you instant breakpoint/single step   
   operation with full view of registers and memory contents.   
      
   cu   
   Michael   
   --   
   Some people have no respect of age unless it is bottled.   
      
   --- SoupGate-Win32 v1.05   
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