Flow breakout

Specifications

Features

• Fast, accurate distance ranging
• Measures absolute range up to 2m
• Measures movement in X/Y using optical sensor
• Power supply and IO 3V - 5V compatible
• Arduino library for easy usage
• Minimum range for motion tracking is 80mm

Mechanical specifications

• Weight: 2.7g
• Size (WxHxD): 20x26x4mm
• Two M2 mounting holes

Electrical specification

• VL53L0x ToF sensor (I2C)
• PMW3901 optical flow sensor (SPI)

• VCC: 3V - 5V

• Compatible with 3 to 5V system (power and IO)
• Optical flow requires an SPI port
• ToF ranger requires an I2C port

Interface specification

• Datasheet
• Schematics

Usage

Functional description

The signal names are marked on the board:

Both sensors are powered by the VCC and GND pins. The board accepts from 3V to 5V, two voltage regulators are generating the required voltage for the sensors and the board has voltage translator for the data signals.

VL53L0 ranging sensor

The VL53L0 ranging sensor is facing front on the board. It is accessible on the I2C pins SCL and SDA.

PMW3901 optical flow sensor

The PMW3901 optical flow sensor is facing front on the board. Is is accessible on the SPI pins CS, MISO, MOSI, CLK. The pins MOTION and /RESET are also connected to the PMW3901. The reset pin can be left floating if not needed.

The optical flow sensor will output motion count. Assuming the board is moving above a flat surface the X/Y orientation is as follow:

Arduino drivers

You can install Arduino libraries using the Arduino library manager.

The VL53L0x has been succesfully tested with the following drivers:

• Adafruit
• Arduino

The PMW3901 arduino driver can be found on github.

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:

#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);
}

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

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

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