How to Draw a Scale Pointer in EEZ Studio
EEZ Studio, while a powerful tool for embedded system development, doesn't directly offer a "scale pointer" drawing function in the same way a dedicated graphics library might. You'll need to build your pointer using the available drawing primitives. This guide will walk you through several approaches, depending on your desired pointer style and the complexity of your application.
Understanding the EEZ Studio Environment
Before diving into drawing techniques, it's crucial to understand that EEZ Studio's graphical capabilities are tied to the hardware you're targeting. The specific functions and limitations will depend on the microcontroller's display capabilities and the drivers you're using. This tutorial assumes you have a basic understanding of EEZ Studio's graphics functions, such as drawing lines, rectangles, and filling shapes.
Method 1: Simple Arrow Pointer
This method creates a basic arrow pointer using lines. It's suitable for simple displays with limited resolution.
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Define Pointer Coordinates: Determine the x and y coordinates of the pointer's base and tip. The base is typically anchored to the scale's value.
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Draw the Arrowhead: Use the
drawLinefunction (or its equivalent in your EEZ Studio library) to draw two short lines forming the arrowhead, originating from the pointer tip. Adjust the angles and lengths to create the desired arrowhead shape. -
Draw the Pointer Shaft: Draw a line from the arrowhead's base to the scale's value point.
Example Code Snippet (Conceptual):
// Assuming 'drawLine' is your EEZ Studio function for drawing lines.
// x1, y1, x2, y2 represent start and end coordinates.
int pointerBaseX = 100; // X coordinate of pointer base
int pointerBaseY = 50; // Y coordinate of pointer base
int pointerTipX = 120; // X coordinate of pointer tip
int pointerTipY = 20; // Y coordinate of pointer tip
drawLine(pointerTipX, pointerTipY, pointerTipX - 5, pointerTipY + 5); //Left side of arrowhead
drawLine(pointerTipX, pointerTipY, pointerTipX + 5, pointerTipY + 5); //Right side of arrowhead
drawLine(pointerBaseX, pointerBaseY, pointerTipX, pointerTipY); //Pointer shaft
Method 2: Filled Triangle Pointer
A filled triangle makes a more visually appealing pointer.
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Define Vertices: Define the three vertices (x, y coordinates) of the triangle, with one vertex at the scale's value point.
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Fill the Triangle: Use the
fillTrianglefunction (or a similar function available in your EEZ Studio library) to fill the triangle with a color.
Example Code Snippet (Conceptual):
// Assuming 'fillTriangle' is your EEZ Studio function.
int pointerBaseX = 100;
int pointerBaseY = 50;
int pointerTipX = 120;
int pointerTipY = 20;
int leftBaseX = 95;
int leftBaseY = 50;
int rightBaseX = 105;
int rightBaseY = 50;
fillTriangle(pointerTipX, pointerTipY, leftBaseX, leftBaseY, rightBaseX, rightBaseY);
Method 3: Using Bitmaps (for Advanced Pointers)
For complex pointer designs, consider using a bitmap.
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Create the Bitmap: Design your pointer graphic using an image editor and convert it into a suitable bitmap format compatible with your EEZ Studio environment.
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Load and Draw the Bitmap: Use the EEZ Studio library's bitmap functions to load the bitmap into memory and draw it at the desired location on the scale. The position would be calculated based on the current scale value.
H2: What are the limitations of drawing a scale pointer in EEZ Studio?
The primary limitation is the lack of built-in, high-level functions specifically for creating pointers. You rely on basic drawing primitives. The complexity you can achieve is directly tied to the capabilities of your target microcontroller's display and the graphics library available within the EEZ Studio environment. Memory constraints may also become a factor for complex bitmap-based pointers.
H2: What types of pointers can I create in EEZ Studio?
You can create a wide variety of pointers, limited only by your creativity and the drawing functions provided by your EEZ Studio configuration. The examples above demonstrate simple arrow and triangle pointers. You could also create more sophisticated designs using combinations of lines, filled shapes, and even bitmaps.
H2: How do I adjust the pointer position based on the scale value?
This requires calculating the pointer's position based on the current scale value. You'll need to map the range of the scale value to the coordinates of the display. A simple linear mapping function can achieve this. For example:
// Assuming 'scaleValue' is the current reading from the scale
// 'minValue' and 'maxValue' are the minimum and maximum values of the scale
// 'displayWidth' is the width of your display
int pointerX = (scaleValue - minValue) * displayWidth / (maxValue - minValue);
This formula calculates the x-coordinate of the pointer based on the proportional value of the current scale reading. You'd then use this calculated pointerX in your drawing functions. You'll need to adjust this based on your display's coordinate system and the scale's orientation.
Remember to replace the placeholder functions (drawLine, fillTriangle, etc.) with the actual functions provided by your specific EEZ Studio setup. Always consult the EEZ Studio documentation and your target hardware's specifications for accurate function names and usage.
