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100 lines
3.9 KiB
100 lines
3.9 KiB
# Detect proximity - Wio Terminal
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In this part of the lesson, you will add a proximity sensor to your Wio Terminal, and read distance from it.
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## Hardware
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The Wio Terminal needs a proximity sensor.
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The sensor you'll use is a [Grove Time of Flight distance sensor](https://www.seeedstudio.com/Grove-Time-of-Flight-Distance-Sensor-VL53L0X.html). This sensor uses a laser ranging module to detect distance. This sensor has a range of 10mm to 2000mm (1cm - 2m), and will report values in that range pretty accurately, with distances above 1000mm reported as 8109mm.
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The laser rangefinder is on the back of the sensor, the opposite side to the Grove socket.
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This is an I<sup>2</sup>C sensor.
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### Connect the time of flight sensor
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The Grove time of flight sensor can be connected to the Wio Terminal.
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#### Task - connect the time of flight sensor
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Connect the time of flight sensor.
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1. Insert one end of a Grove cable into the socket on the time of flight sensor. It will only go in one way round.
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1. With the Wio Terminal disconnected from your computer or other power supply, connect the other end of the Grove cable to the left-hand side Grove socket on the Wio Terminal as you look at the screen. This is the socket closest to from the power button. This is a combined digital and I<sup>2</sup>C socket.
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1. You can now connect the Wio Terminal to your computer.
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## Program the time of flight sensor
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The Wio Terminal can now be programmed to use the attached time of flight sensor.
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### Task - program the time of flight sensor
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1. Create a brand new Wio Terminal project using PlatformIO. Call this project `distance-sensor`. Add code in the `setup` function to configure the serial port.
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1. Add a library dependency for the Seeed Grove time of flight distance sensor library to the projects `platformio.ini` file:
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```ini
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lib_deps =
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seeed-studio/Grove Ranging sensor - VL53L0X @ ^1.1.1
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```
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1. In `main.cpp`, add the following below the existing include directives to declare an instance of the `Seeed_vl53l0x` class to interact with the time of flight sensor:
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```cpp
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#include "Seeed_vl53l0x.h"
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Seeed_vl53l0x VL53L0X;
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```
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1. Add the following to the bottom of the `setup` function to initialize the sensor:
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```cpp
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VL53L0X.VL53L0X_common_init();
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VL53L0X.VL53L0X_high_accuracy_ranging_init();
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```
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1. In the `loop` function, read a value from the sensor:
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```cpp
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VL53L0X_RangingMeasurementData_t RangingMeasurementData;
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memset(&RangingMeasurementData, 0, sizeof(VL53L0X_RangingMeasurementData_t));
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VL53L0X.PerformSingleRangingMeasurement(&RangingMeasurementData);
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```
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This code initializes a data structure to read data into, then passes it into the `PerformSingleRangingMeasurement` method where it will be populated with the distance measurement.
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1. Below this, write out the distance measurement, then delay for 1 second:
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```cpp
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Serial.print("Distance = ");
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Serial.print(RangingMeasurementData.RangeMilliMeter);
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Serial.println(" mm");
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delay(1000);
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```
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1. Build, upload and run this code. You will be able to see distance measurements with the serial monitor. Position objects near the sensor and you will see the distance measurement:
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```output
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Distance = 29 mm
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Distance = 28 mm
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Distance = 30 mm
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Distance = 151 mm
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```
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The rangefinder is on the back of the sensor, so make sure you use the correct side when measuring distance.
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> 💁 You can find this code in the [code-proximity/wio-terminal](code-proximity/wio-terminal) folder.
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😀 Your proximity sensor program was a success!
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