Getting started with Flow breakout board

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Flow breakout board

This getting started will walk you through the process of getting sensor values from the Flow breakout board using an Arduino UNO. The process should be applicable to any arduino-compatible board that has I2C and SPI support.

Hardware requirements

To follow this getting started guide you will need:

Electrical cabling

The flow breakout board contains two sensors: the PMW3901 optical flow sensor which has an SPI interface and the VL53L0x ToF ranging sensor which has an I2C interface. To use both sensors, both interfaces have to be connected to the Arduino:

Flow breakout Arduino uno cabling

Code

Start the Arduino IDE and create a new sketch. Load the following libraries using the library manager:

  • VL53L0X
  • Bitcraze_PMW3901

Then copy-paste the following code into the sketch and execute it.

#include "Bitcraze_PMW3901.h"
#include <Wire.h>
#include <VL53L0X.h>

VL53L0X rangeSensor;

// Using digital pin 10 for chip select
Bitcraze_PMW3901 flow(10);

void setup() {
  Serial.begin(9600);

  // Initialize flow sensor
  if (!flow.begin()) {
    Serial.println("Initialization of the flow sensor failed");
    while(1) { }
  }

  // Initialize range sensor
  Wire.begin();

  rangeSensor.init();
  rangeSensor.setTimeout(500);
}

int16_t deltaX,deltaY;

void loop() {
  // Get motion count since last call
  flow.readMotionCount(&deltaX, &deltaY);

  // Get single range measurement
  float range = rangeSensor.readRangeSingleMillimeters();

  Serial.print("X: ");
  Serial.print(deltaX);
  Serial.print(", Y: ");
  Serial.print(deltaY);
  Serial.print(", Range: ");
  if (range > 5000) {
    Serial.print("N/A");
  } else {
    Serial.print(range);
  }
  Serial.print("\n");

  delay(100);
}

Output

Open the serial console to see the output from the sensors. If nothing is moving in front of the sensor and the closest object is far away you should see the output below:

X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A
X: 0, Y: 0, Range: N/A

If you point the sensor upwards and wave your hand above it you should see something similar to the output below:

X: -1, Y: 0, Range: 123
X: 43, Y: 64, Range: 134
X: 71, Y: 121, Range: 137
X: -1, Y: 39, Range: 123
X: -96, Y: -64, Range: 120
X: -96, Y: -161, Range: 110
X: 32, Y: 0, Range: 123
X: 0, Y: 0, Range: 122
X: 53, Y: 45, Range: 122
X: 21, Y: 133, Range: 118