STM32F103 Dual-Channel Temperature Monitoring and Alarm System

Project Overview

This dual-channel temperature monitor targets an STM32F103C8T6 minimum board. It samples a digital DS18B20 and the voltage from a PT100 module, drives an OLED and alarms, logs CSV to an SD card, accepts serial commands and stores thresholds across power cycles. An ESP-01S cloud workflow is reserved but disabled by default.

Project Goals

• Acquire digital and analog temperature channels together.
• Adjust thresholds from keys or serial commands and retain them in Flash.
• Provide alarms, min/max tracking, SD CSV logs and status diagnostics.
• Keep Keil, CubeMX and GCC outputs together with complete wiring documents.

Technology and Environment

C, STM32 HAL, ADC, 1-Wire, I2C, SPI, FatFs, UART, internal Flash, non-blocking periodic scheduling and debounced limit decisions. Hardware includes the STM32F103C8T6, ST-Link, DS18B20, PT100 voltage module, SSD1306 OLED, SD SPI module, keys, buzzer and alarm LED. Serial is 115200 8N1.

System Architecture

The main loop uses independent millisecond timestamps. Sampling updates channel values and ranges; the alarm block requires two consecutive violations; the display refreshes only after content changes; FatFs appends CSV records; and UART receives and parses whole lines without blocking.

Functional Modules

• app_ds18b20.c, app_pt100.c: two sensing paths.
• app_alarm.c, app_keys.c: alarm output and key configuration.
• app_oled.c: status, thresholds and min/max display.
• app_storage.c: SD-card CSV logging.
• app_settings.c: persistent storage for four thresholds.
• app.c: state aggregation, serial commands and periodic scheduling.

Implementation

1. Configure ADC, I2C, SPI, UART and GPIO from the pin table.
2. Verify DS18B20 and PT100 conversion independently.
3. Add thresholds, two-sample confirmation and audible/visual alarms.
4. Integrate the OLED, short/long key presses and Flash storage.
5. Integrate FatFs logs and serial commands.
6. Generate the Keil project, GCC HEX and user documentation.

Key Code

Threshold pairs are normalized before persistence, and alarm cadence uses the system tick instead of a blocking delay:

void Alarm_Task(uint8_t enabled)
{
    static uint32_t last_toggle = 0;
    static uint8_t state = 0;
    if (!enabled) {
        state = 0;
        Alarm_Set(0);
        return;
    }
    if ((HAL_GetTick() - last_toggle) >= 200U) {
        state ^= 1U;
        Alarm_Set(state);
        last_toggle = HAL_GetTick();
    }
}

Debugging and Verification

Bring-up proceeds through MCU and ST-Link, one sensor at a time, OLED, alarm, keys, SD and serial. PB3/PB4 key use requires disabling full JTAG while retaining Serial Wire. OLED SD status and error counts help isolate card failures.

Problems and Solutions

PB3/PB4 conflict with default JTAG, PT100 module output may exceed the 3.3 V ADC limit, one bad sample can cause false alarms, and SD power or formatting can fail. The design fixes debug mode to SWD, requires input-voltage checks, confirms two consecutive violations and exposes storage status and error counters. FAT32, insertion before power-on and a common ground are documented requirements.

Current Result

The repository contains a complete HAL project, Keil project, CubeMX configuration, FatFs, documentation and a flashable HEX image. Defaults are 15-second sampling and logging, 10–60 °C for DS18B20 and 0–100 °C for PT100. Cloud support remains a documented flow, not a claimed deployed feature.

Summary

The project integrates acquisition, interaction, persistence and fault status in one STM32 exercise. Sensor accuracy, PT100 calibration and long-term SD reliability still require physical acceptance testing.

GitHub Repository

Open TemperatureInspector_STM32F103C8T6