digraph {
    node        [shape = "rect", style = "rounded", fontname = "JetBrainsMono"];
    entry       [label = "", shape = "circle", style = "filled", color = "black"];
    adc_init    [label = "initialise ADC"];
    loop        [label = "", shape = "circle", style = "filled", color = "gray"];

    entry -> adc_init
    adc_init -> loop
    loop -> entry
}