STM32 Mbed CodeIDE (8/8): integrated controller capstone

Embedded systems become useful when several small skills work together: read a level, decide what state it belongs to, show a visible warning, and print enough evidence to trust the result.

The controller uses one potentiometer as simulated receiver pressure and one button as an alarm acknowledge control. In a real installation, a calibrated pressure transmitter and safety-rated protection would be required; this training controller only practices indication and acknowledgement logic.

Hardware map used by the starter controller:

- PC_1 is the simulated pressure input, controlled by the Pot. pot2 slider.
- PC_5 is the acknowledge button input, controlled by the B1 button.
- PA_8, PA_9, and PA_10 are the RGB PWM channels.
- PB_13 is the active-low green status LED.

Read this map as a set of Mbed objects working together: AnalogIn reads the level, DigitalIn reads the acknowledge button, PwmOut drives the RGB channels, and DigitalOut drives the status LED. The capstone is mainly about connecting those API pieces into one readable controller.

The required behavior is:

- Level below 40%: RGB output green, status LED off, serial evidence like
percent=25 level=SAFE ack=0.
- Level from 40% to 69%: RGB output yellow, status LED off, serial evidence like
percent=55 level=WARNING ack=0.
- Level 70% or higher with the button released: RGB output red, status LED
blinking, serial evidence like percent=80 level=CRITICAL ack=0. Watch
for at least two seconds before recording this state; count it as blinking
only if the status LED turns on and off repeatedly.
- Level 70% or higher after the button has been pressed once: RGB output blue,
status LED off, serial evidence like percent=80 level=CRITICAL ack=1.
Releasing the button does not remove the acknowledgement while the level
remains critical.

The acknowledge button does not reduce pressure or make a critical condition safe. It latches only the local indication so the operator can show that the alarm has been noticed; level=CRITICAL must remain in the serial evidence. The latch clears automatically after the simulated pressure falls below the critical threshold.

#include "mbed.h"

AnalogIn level_control(PC_1);
DigitalIn acknowledge_button(PC_5, PullUp);

PwmOut rgb_red(PA_8);
PwmOut rgb_green(PA_9);
PwmOut rgb_blue(PA_10);

DigitalOut status_led(PB_13, 1);

constexpr int warning_threshold_percent = 40;
constexpr int critical_threshold_percent = 70;

void status_on() {
    status_led = 0;
}

void status_off() {
    status_led = 1;
}

void set_rgb(float red, float green, float blue) {
    rgb_red.write(red);
    rgb_green.write(green);
    rgb_blue.write(blue);
}

void show_safe() {
    set_rgb(0.0f, 0.7f, 0.0f);
    status_off();
}

void show_warning() {
    set_rgb(0.7f, 0.5f, 0.0f);
    status_off();
}

void show_critical(bool acknowledged) {
    if (acknowledged) {
        set_rgb(0.0f, 0.0f, 0.8f);
        status_off();
    } else {
        set_rgb(0.9f, 0.0f, 0.0f);
        status_led = !status_led.read();
    }
}

int main() {
    rgb_red.period_ms(2);
    rgb_green.period_ms(2);
    rgb_blue.period_ms(2);

    printf("Integrated controller start\n");

    bool acknowledged = false;

    while (true) {
        float reading = level_control.read();
        int percent = (int)(reading * 100.0f);
        // TODO 1: replace false with the active-low button expression.
        bool button_pressed = false;

        if (percent < critical_threshold_percent) {
            acknowledged = false;
        } else if (button_pressed) {
            acknowledged = true;
        }

        if (percent < warning_threshold_percent) {
            show_safe();
            printf("percent=%d level=SAFE ack=%d\n",
                   percent,
                   acknowledged);
        // TODO 2: replace false with the WARNING-range threshold test.
        } else if (false) {
            show_warning();
            printf("percent=%d level=WARNING ack=%d\n",
                   percent,
                   acknowledged);
        } else {
            show_critical(acknowledged);
            printf("percent=%d level=CRITICAL ack=%d\n",
                   percent,
                   acknowledged);
        }

        ThisThread::sleep_for(500ms);
    }
}

Prepare and then fill the table in two passes. Before the build, select each Test case, choose the planned button action, and write its Expected response as RGB color plus status-LED behavior. During the live test, enter the actual integer pressure percentage, visible response, and full serial line. Percent is a simulated transmitter percentage, not pressure in bar. For critical-unacknowledged, write blinking only after at least two seconds. For critical-acknowledged, press and release the button and record a later line showing that ack=1 persisted. Leave extra unused rows completely blank.

The controller above is a starting point. Choose one improvement, implement it in main.cpp, then save, compile, upload, and test it on the receiver-alarm scenario. A plan without running code is not enough.

Choose one bounded improvement:

- Threshold route: change only critical_threshold_percent to a value from
72% to 80%. Choose one fixed test value between 70% and your new threshold,
so the same input changes branch after your edit.
- Very-high route: add a VERY_HIGH branch for values of 90% or more,
immediately before the ordinary critical branch. Give it a magenta RGB
indication, a steady-on status LED, and level=VERY_HIGH serial evidence.
Use 95% with the button released for the before/after test, then check 80%
once to confirm that ordinary critical behavior still works.

Use the matching starter-controller row as your before evidence. Implement the change, save, compile, and upload; this is planned build 2 of 2. Test the same input/button action again for after evidence. Record a complete serial line and visible RGB/status behavior for both versions. If you chose the very-high route, run the additional 80% regression check and report it in the final explanation.