README

This sample calculates a fractal image on each CPU core from a Mandelbrot set
and displays it to put some load onto the CPU. It may be build for single- or
multi-core operation.

A CPU temperature chart will be displayed at the bottom of the screen. The chart
is updated every two seconds. A horizontal white line is drawn every 20 degrees
Celsius and a red line for the maximum allowed temperature of 85 degrees
Celsius.

Before building you should set the DEPTH define in include/circle/screen.h to 16
to increase the number of available colors. If you want to run this sample with
multiple cores on the Raspberry Pi 2/3/4 you have to define ARM_ALLOW_MULTI_CORE
in include/circle/sysconfig.h.

The behaviour of the sample can be influenced by two options which may be
defined in the file cmdline.txt:

fast=true	Set maximum CPU speed (default is low speed on Raspberry Pi 2/3/4)

socmaxtemp=60	Set maximum temperature of the SoC (the main chip) to be enforced
		in degrees Celsius (range 40 to 78, default 60)

gpiofanpin=2	GPIO pin number (SoC number, not header position) to which the
		control line of a (Raspberry Pi 4) Case Fan is connected. The fan
		will be switched on, when "socmaxtemp" will be reached. The CPU
		speed is not throttled, when this option is used. Please note that
		the default GPIO pin 14 for the Case Fan cannot be used in this
		sample, because is it assigned to the serial interface here.
