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From: Michael Schwingen <news-1513678000@discworld.dascon.de>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Need help with PI PICO...
Date: 24 Mar 2024 13:31:48 GMT
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On 2024-03-23, The Natural Philosopher <tnp@invalid.invalid> 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.