Car dashboard graphic library

Introduction

This C library implements drawing functions for common car dashboard controls. It was commissioned by a friend who is working on an embedded project, so it's as fast and as decoupled from the hardware as possible (the library itself invokes architecture specific functions defined in screen.h and utils.h, the implementations of which can be modified without altering the controls' code).

A demo running on Linux framebuffer is provided.

It was developed with an 80MHz ST32 Nucleo-64 on mind, so it probably won't run fast enough on an Arduino, but it certainly will on a Raspberry Pi (and since it uses the framebuffer, none of the functions needs to be changed).

Compilation

Simply run make.

Execution

From a real terminal (e.g. after hitting CTRL + ALT + F2) run ./Dashboard.

Implemented controls

Each control is composed of a struct which keeps track of the internal state of the control and of three functions:

• init_<controlname>(...) Instantiates the control and draws it
• update_<controlname>(..., uint8_t ...) Displays a value (or more) from 0 (min) to 255 (max) inside the control
• delete_<controlname>(...) Deallocates the control and clears the region of the screen it was placed in.

Each control structure has two colors (which can be changed at any moment):

• fg The color with which the control will be painted
• bg The background color with which the control's old value will be cleared.

Accelerometer

• Displays two values orthogonally by moving a cross
• A circular or square outline can be chosen, with any number of concentric rings.

Bar

• Displays a single value in a bar growing either horizontally or vertically.

Dial

• Displays a single value in a dial either with a clockwise (0 is on the left, 255 is on the right) or a counterclockwise rotation
• Arc length and phase of the dial can be chosen, as well as an arbitrary number of ticks dividing the quadrant.

Plot

• Displays a plot of a single value over time (measured as number of times update_plot(...) was called)
• The x axis of the plot moves forward by one pixel, modulo the control's width
• The y axis of the plot is scaled with the control's height (0 -> 0 and 255 -> height).

Radar

• Displays a radar plot of an arbitrary number of values
• The radar can be divided into an arbitrary number of concentric circles and the values can be displayed either with a filled or an empty polygon.

Important note: the polygon filling function is very slow, so this control might be unsuitable for embedded devices.

Symbols & text

• A dashboard symbol can be displayed or deleted
• Single ASCII-7 characters or null-terminated strings can be written on screen
• Strings are broken into multiple lines when a \\n is encountered.