Add Getting Started tutorial for Vision Shield (Arduino) (#88)

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* Revision of the Vision Shield Getting Started Tutorial (#83)

* Change title

* Fix broken image path

* Clean up formatting

* Fix typos and rephrase content up to chapter 4

* Add explanations for updated sketch

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* Update vs_ard_gs_cover.png

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Co-authored-by: Sebastian Romero <s.romero@arduino.cc>
Co-authored-by: Sebastian Romero <s.hunkeler@arduino.cc>

Author: Lenardgeorge

content/tutorials/portenta-h7/vs-ard-gs/assets/vs_ard_frames_captured.png

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+---
+title: Getting Started With The Vision Shield Camera
+coverImage: assets/vs_ard_gs_cover.svg
+tags: [Getting Started, Camera, Processing, Serial]
+description: This tutorial shows you how to capture frames from the Vision Shield Camera module and visualise the video output through a Processing sketch.
+---
+
+# Getting Started With The Vision Shield Camera 
+## Overview
+This tutorial shows you how to capture frames from the Vision Shield Camera module and visualise the video output through a Processing sketch.
+
+### You Will Learn
+- Capturing the frames from the camera.
+- Sending the frames as a byte stream through a Serial connection.
+- Visualising the frames in Processing. 
+
+### Required Hardware and Software
+- [Portenta H7 board](https://store.arduino.cc/portenta-h7)
+- Portenta Vision Shield ( [LoRa](https://store.arduino.cc/portenta-vision-shield-lora) or [Ethernet](https://store.arduino.cc/portenta-vision-shield) )
+- USB C cable (either USB A to USB C or USB C to USB C)
+- Arduino IDE 1.8.10+
+- Processing 3.5.4+
+
+## Instructions
+Accessing the Vision Shield's camera data is done with the help of both Arduino and the Processing IDE. The Arduino sketch handles the capture of image data by the on-board camera while the java applet created with Processing helps to visualise this data with the help of a serial connection. The following steps will run you through how to capture, package the data through the serial port and visualise the output in Processing. 
+
+### 1. The Basic Setup
+Connect the Vision Shield to your Portenta H7 as shown in the figure. The top and Bottom high density connecters the aligned with and are connected to the concurrent ones on the Portenta board. Plug in the H7 to your computer using the USB C cable. 
+
+![Connecting the Vision Shield to Portenta](assets/vs_ard_gs_attach_boards.svg)
+
+Open the board manager in the Arduino IDE and install the latest version of the Portenta Core which is [v1.3.2](https://github.com/arduino/ArduinoCore-mbed/releases/tag/1.3.2)
+
+![Download the mbed core](assets/vs_ard_gs_core.png)
+
+### 2. Capturing the Frames
+
+Create a new Arduino sketch called `CameraCaptureRawBytes.ino`.
+
+To capture the frames you will need to use the functions contained in `camera.h` which comes with the Portenta core. This library contains all APIs related to frame capturing, motion detection and pattern recognition. Include the header file in your sketch.
+
+```cpp
+#include "camera.h"
+```
+
+Next, let's intialise a camera object and a frame buffer of the size 320*240 (76'800 bytes).
+
+```cpp
+CameraClass cam;
+uint8_t fb[320*240];
+```
+
+In the `setup()` function, let's start the Serial communication at `921600` baud rate and iniitialise the camera using `cam.begin()`. 
+
+```cpp
+void setup() {
+  Serial.begin(921600);
+  //Init the cam QVGA, 30FPS
+  cam.begin(CAMERA_R320x240, 30);
+}
+```
+
+In the loop we need to capture each Frame and send it over a serial connection to the Processing sketch that will display the frames. We will use the `grab(uint8_t *buffer, uint32_t timeout=5000);` function to fetch the frame from the frame buffer and save it into our custom data buffer. 
+
+```cpp
+void loop() {
+  // put your main code here, to run repeatedly:
+  
+  // Wait until the receiver acknowledges
+  // that they are ready to receive new data
+  while(Serial.read() != 1){};
+  
+  // Grab frame and write to serial
+  if (cam.grab(fb) == 0) {
+     Serial.write(fb, 320*240);       
+  }
+  
+}
+```
+
+### 3. Create the Processing Sketch 
+Open a new processing sketch file and name it `CameraCapture.pde`. 
+
+![Create a processing sketch](assets/vs_ard_open_pde_sketch.png)
+
+Let's start by importing the libraries and initialising the variables you will need to process the captured data. To process the data sent by the Vision Shield you will need to import the following libraries:
+
+- `processing.serial.*` : a [Serial Library](https://processing.org/reference/libraries/serial/index.html)  that is used to read and write data to external devices over the serial line. 
+- `java.nio.ByteBuffer`  : a java class that provides access to operations on byte buffers
+
+```java
+import processing.serial.*;
+import java.nio.ByteBuffer;
+```
+
+Next we initialise the following variables to process the received pixels from the serial port. We set the dimensions, pixel count, and bytes required per frame. 
+
+```java
+// must match resolution used in the sketch
+final int cameraWidth = 320;
+final int cameraHeight = 240;
+final int cameraBytesPerPixel = 1;
+final int cameraPixelCount = cameraWidth * cameraHeight;
+final int bytesPerFrame = cameraWidth * cameraHeight * cameraBytesPerPixel;
+```
+
+To recieve the frames you will need a Serial port, a PImage object and an array to store the pixel values of the frame. Add the following variables to the code. 
+
+```java
+Serial myPort;
+PImage myImage;
+byte[] frameBuffer = new byte[bytesPerFrame];
+int pixelPosition = 0;
+int lastUpdate = 0;
+boolean shouldRedraw = false;
+```
+
+Here we will establish a connection to the serial port and prepare the buffer to store the frame pixels. Additionally we send a byte to the Arduino sketch from Processing to let it know that it's ready to receive data.
+
+```java
+void setup() {
+  size(640, 480);
+  
+  // if you know the serial port name
+  //myPort = new Serial(this, "COM5", 921600);                  // Windows
+  //myPort = new Serial(this, "/dev/ttyACM0", 921600);          // Linux
+  myPort = new Serial(this, "/dev/cu.usbmodem14101", 921600);   // Mac
+ 
+  // Set the number of bytes to buffer 
+  myPort.buffer(bytesPerFrame)
+  
+  // Create an image based on the camera's dimensions and format
+  myImage = createImage(cameraWidth, cameraHeight, ALPHA);
+
+  // Let the Arduino sketch know we're ready to receive data
+  myPort.write(1);
+}
+```
+
+The draw function checks if the connection is still alive and if there is any new data that can be drawn as an image. In that case the original image gets copied into a new image object so that it can be scaled up.
+
+```java
+void draw() {
+  // Time out after 1.5 seconds and ask for new data
+  if(millis() - lastUpdate > 1500) {
+    println("Connection timed out.");
+    myPort.clear();
+    myPort.write(1);
+  }
+  
+  if(shouldRedraw){    
+    PImage img = myImage.copy();
+    img.resize(640, 480);
+    image(img, 0, 0);
+    shouldRedraw = false;
+  }
+}
+```
+
+### 4. Visualing the Frames
+For this step, you will use the `serialEvent()` callback function to update the `myImage` when a new data is received on the serial port.
+
+```java
+void serialEvent(Serial myPort) {
+  lastUpdate = millis();
+  
+  // read the received bytes
+  myPort.readBytes(frameBuffer);
+
+  // Access raw bytes via byte buffer  
+  ByteBuffer bb = ByteBuffer.wrap(frameBuffer);
+
+  int i = 0;
+
+  while (bb.hasRemaining()) {
+    // read 8-bit pixel
+    byte pixelValue = bb.get();
+
+    // set pixel color
+    myImage.pixels[i++] = color(Byte.toUnsignedInt(pixelValue));    
+  }
+  
+  myImage.updatePixels();
+  
+  // Ensures that the new image data is drawn in the next draw loop
+  shouldRedraw = true;
+  
+  // Let the Arduino sketch know we received all pixels
+  // and are ready for the next frame
+  myPort.write(1);
+}
+```
+
+The first thing we do inside this method is to update the timestamp for when the last data was read. This is to detect and recover from a connection timeout. Then read the bytes from the `frameBuffer` array which you can do with the help of the [`readBytes()`](https://processing.org/reference/libraries/serial/Serial_readBytes_.html) method that returns the number of bytes read.
+
+```java
+lastUpdate = millis();
+  
+// read the received bytes
+myPort.readBytes(frameBuffer);
+```
+
+Then the frame buffer is translated into a ByteBuffer that allows for easy and safe access to the underlying bytes without having to worry about the array indices.
+
+```cpp
+// Access raw bytes via byte buffer  
+ByteBuffer bb = ByteBuffer.wrap(frameBuffer);
+```
+
+Next we read the frame buffer and convert the bytes into pixel color values. The image gets constructed by sequentially filling the pixels array of the image. The conversion of the raw data is done wih [`color()`](https://processing.org/reference/color_.html) and [`Byte.toUnsignedInt()`](https://docs.oracle.com/javase/8/docs/api/java/lang/Byte.html).
+
+```java
+int i = 0;
+
+while (bb.hasRemaining()) {
+  // read 8-bit pixel
+  byte pixelValue = bb.get();
+
+  // set pixel color
+  myImage.pixels[i++] = color(Byte.toUnsignedInt(pixelValue));    
+} 
+```
+
+Once all the pixels have been updated, you need to tell the sketch to redraw the image. Additionally we send an acknowledgement back to the arduino sketch to ask it to send the pixels for the next frame. We update the image with `updatePixels()` and write `1` to the serial port for the acknowledgement.
+
+```  cpp
+myImage.updatePixels();
+
+// Ensures that the new image data is drawn in the next draw loop
+shouldRedraw = true;
+
+// Let the Arduino sketch know we received all pixels
+// and are ready for the next frame
+myPort.write(1);
+```
+
+### 5. Upload the Sketch
+
+Select the right serial port on your IDE and upload the Arduino sketch to your H7. After a successful upload, run the `CameraViewer.pde` sketch in Processing. You should be able to see the rendered camera output on the Processing canvas.
+
+![Camera output on Processing](assets/vs_ard_frames_captured.png)
+
+## Conclusion
+
+In this tutorial you learnt how to capture the frames from your Vision Shield's Camera and to visualise the  frames throught Processing. This knowledge can be useful for you to build and experiment simple computer vision applications for both outdoor and indoor environments. 
+
+### Complete Sketch
+The `CaptureRawBytes.ino` Sketch. 
+
+```cpp
+#include "camera.h"
+
+CameraClass cam;
+uint8_t fb[320*240];
+
+void setup() {
+  Serial.begin(921600);  
+
+  // Init the cam QVGA, 30FPS
+  cam.begin(CAMERA_R320x240, 30);
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+  
+  // Wait until the receiver acknowledges
+  // that they are ready to receive new data
+  while(Serial.read() != 1){};
+  
+  // Grab frame and write to serial
+  if (cam.grab(fb) == 0) {
+     Serial.write(fb, 320*240);       
+  }
+  
+}
+```
+
+The `CameraViewer.pde` Sketch. 
+
+```java
+/*
+  This sketch reads a raw Stream of RGB565 pixels
+  from the Serial port and displays the frame on
+  the window.
+  Use with the Examples -> CameraCaptureRawBytes Arduino sketch.
+  This example code is in the public domain.
+*/
+
+import processing.serial.*;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+Serial myPort;
+
+// must match resolution used in the sketch
+final int cameraWidth = 320;
+final int cameraHeight = 240;
+final int cameraBytesPerPixel = 1;
+final int cameraPixelCount = cameraWidth * cameraHeight;
+final int bytesPerFrame = cameraPixelCount * cameraBytesPerPixel;
+
+PImage myImage;
+byte[] frameBuffer = new byte[bytesPerFrame];
+int lastUpdate = 0;
+boolean shouldRedraw = false;
+
+void setup() {
+  size(640, 480);
+
+  // if you have only ONE serial port active
+  //myPort = new Serial(this, Serial.list()[0], 921600);          // if you have only ONE serial port active
+
+  // if you know the serial port name
+  //myPort = new Serial(this, "COM5", 921600);                    // Windows
+  //myPort = new Serial(this, "/dev/ttyACM0", 921600);            // Linux
+  myPort = new Serial(this, "/dev/cu.usbmodem14401", 921600);     // Mac
+
+  // wait for full frame of bytes
+  myPort.buffer(bytesPerFrame);  
+
+  myImage = createImage(cameraWidth, cameraHeight, ALPHA);
+  
+  // Let the Arduino sketch know we're ready to receive data
+  myPort.write(1);
+}
+
+void draw() {
+  // Time out after 1.5 seconds and ask for new data
+  if(millis() - lastUpdate > 1500) {
+    println("Connection timed out.");
+    myPort.clear();
+    myPort.write(1);
+  }
+  
+  if(shouldRedraw){    
+    PImage img = myImage.copy();
+    img.resize(640, 480);
+    image(img, 0, 0);
+    shouldRedraw = false;
+  }
+}
+
+void serialEvent(Serial myPort) {
+  lastUpdate = millis();
+  
+  // read the received bytes
+  myPort.readBytes(frameBuffer);
+
+  // Access raw bytes via byte buffer  
+  ByteBuffer bb = ByteBuffer.wrap(frameBuffer);
+  
+  /* 
+    Ensure proper endianness of the data for > 8 bit values.
+    When using > 8bit values uncomment the following line and
+    adjust the translation to the pixel color. 
+  */     
+  //bb.order(ByteOrder.BIG_ENDIAN);
+
+  int i = 0;
+
+  while (bb.hasRemaining()) {
+    // read 8-bit pixel
+    byte pixelValue = bb.get();
+
+    // set pixel color
+    myImage.pixels[i++] = color(Byte.toUnsignedInt(pixelValue));    
+  }
+  
+  myImage.updatePixels();
+  
+  // Ensures that the new image data is drawn in the next draw loop
+  shouldRedraw = true;
+  
+  // Let the Arduino sketch know we received all pixels
+  // and are ready for the next frame
+  myPort.write(1);
+}
+```
+
+**Authors:** Lenard George, Sebastian Romero  
+**Reviewed by:** Sebastian Romero [2021-04-26]  
+**Last revision:** Sebastian Romero [2021-04-26]

content/tutorials/portenta-h7/vs-ard-gs/assets/vs_ard_gs_attach_boards.svg

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