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Zumo 32U4 proximity sensor doesn't seem to work passively


Hi all,

I have a few Zumo 32U4 robots and I’ve noticed that in the Demo code it shows the following:

// Display proximity sensor readings.
void proxSensorDemo()

  while (buttonMonitor() != 'B')
    bool proxLeftActive = proxSensors.readBasicLeft();
    bool proxFrontActive = proxSensors.readBasicFront();
    bool proxRightActive = proxSensors.readBasicRight();

    lcd.gotoXY(0, 0);
    lcd.print(' ');
    lcd.print(' ');

    // On the last 3 characters of the second line, display
    // basic readings of the sensors taken without sending
    // IR pulses.
    lcd.gotoXY(5, 1);

The active sensing when IR pulses are sent works fine. However, the passive sensing of IR signals doesn’t seem to work. proxLeftActive, proxFrontActive, and proxRightActive are always zero, even when I have another actively sensing robot nearby sending IR pulses.

Any suggestions?



I suspect the issue is caused by either poor or improper connections on your Zumo 32U4 robots, because those functions (readBasicLeft, readBasicFront, and readBasicRight), which call readBasic, perform a quick digital reading of the specified sensor and return a 1 if the object is configured or 0 if not configured. (For more details about those functions, see Zumo32U4ProximitySensors.cpp in the Zumo 32U4’s Arduino library on our GitHub page.)

Can you detach the front sensor array on one of your Zumo 32U4 robots and post close-up pictures showing both sides of the board and the associated header pins on the Zumo 32U4 board? I want to double-check your soldering connections between both boards and the jumper placements on the front sensor array.

- Amanda


Hi Amanda, thank you for responding!

Sure thing:

Will these do?

The photos are from a brand new, factory assembled Sumo 32U4.

Just thinking out loud, if there was a hardware problem I think I would be missing some or all of the sensor readings in that bar graph display for the sensors receiving the IR pulses.

Is it possible there’s a configuration issue with the sensors in the demo?


Hi again, I sorted the issue out. Here’s a photo:

The bar graph in the lower right of the LCD was what I was looking for. It’s the proximity sensor detecting external IR from another Zumo.

Sorry for the confusion!


That’s great! I’m glad you were able to resolve your issue; thank you for letting us know.

- Amanda