Edit with Answer:  I had forgot to switchback to using BCM pin numbering from DPI.


Thanks for the helpful comments.

My Sonic Sensor is reporting only zero cm and I don't know how to troubleshoot it. It was working for a time, but something's gone wrong and I can't find what.

I have a spare sensor and have swamped them out with the same result so I don't think that's it. I didn't change any wiring on the breadboard between the success and failure so I don't think that's it.

My code is below and I've attached a screen shot of the results of the last test of it running with my hand moving in front of the sensor.

What should I test next?

# https://github.com/MarkAHeywood/Bluetin_Python_Echo
from Bluetin_Echo import Echo  # HCSR04 Module
from time import sleep

DistSense = Echo(19, 20)

def report_dist():
samples = 4
    while True:
        d = DistSense.read('cm', samples)
        print(d, 'cm')
except KeyboardInterrupt:



print('End Of File.')

Terminal Output

  • Perhaps try different software? Here is one of my pigpio examples abyz.me.uk/rpi/pigpio/…
    – joan
    Jul 26, 2020 at 16:08
  • Thanks for the suggestion. I also tried it with the CircuitPython module and got the same result. circuitpython-hcsr04.readthedocs.io/en/latest/api.html
    – ManOAction
    Jul 26, 2020 at 16:10
  • We need a picture of the wiring and voltage divider circuit please. You can edit the question to add them in.
    – user115418
    Jul 26, 2020 at 16:40
  • Thanks ya'll. It was a mixup between using BCM and DPI pin numbering.
    – ManOAction
    Jul 26, 2020 at 18:21

1 Answer 1


I needed to use BCM Pin numbering instead of DPI.

It was the switching between HC-SR04 modules that tripped me up. The Adafruit Circuit Pi modules were using DPI and the Bluetin Echo modules was using BCM.

Thanks for the help and comments!

  • Please accept your own answer with a click on the tick on its left side. Only this will finish the question and it will not pop up again year for year.
    – Ingo
    Jul 29, 2020 at 8:59

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