• MCU: STM32F103C8T6
• Suggested framework: STM32Cube HAL / PlatformIO or STM32CubeIDE
• Debug/programming: SWD on PA13/PA14, NRST on MCU_NRST

C
#include "main.h"

ADC_HandleTypeDef hadc1;
I2C_HandleTypeDef hi2c1;
UART_HandleTypeDef huart1;
UART_HandleTypeDef huart2;

#define LTE_PWRKEY_GPIO_Port GPIOB
#define LTE_PWRKEY_Pin GPIO_PIN_0
#define LTE_RESET_GPIO_Port GPIOB
#define LTE_RESET_Pin GPIO_PIN_1
#define LTE_STATUS_GPIO_Port GPIOB
#define LTE_STATUS_Pin GPIO_PIN_2
#define STATUS_LED_GPIO_Port GPIOB
#define STATUS_LED_Pin GPIO_PIN_5
#define DS18B20_GPIO_Port GPIOB
#define DS18B20_Pin GPIO_PIN_8
#define DHT22_GPIO_Port GPIOB
#define DHT22_Pin GPIO_PIN_9
#define RELAY_CTRL_GPIO_Port GPIOB
#define RELAY_CTRL_Pin GPIO_PIN_10

static void LTE_SendAT(const char *cmd) {
    HAL_UART_Transmit(&huart2, (uint8_t*)cmd, strlen(cmd), HAL_MAX_DELAY);
    HAL_UART_Transmit(&huart2, (uint8_t*)"\r\n", 2, HAL_MAX_DELAY);
}

uint16_t Read_ACS712_ADC(void) {
    HAL_ADC_Start(&hadc1);
    HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);
    return HAL_ADC_GetValue(&hadc1);
}

int main(void) {
    HAL_Init();
    SystemClock_Config();
    MX_GPIO_Init();
    MX_ADC1_Init();
    MX_I2C1_Init();
    MX_USART1_UART_Init();
    MX_USART2_UART_Init();

    HAL_GPIO_WritePin(RELAY_CTRL_GPIO_Port, RELAY_CTRL_Pin, GPIO_PIN_RESET);
    HAL_GPIO_WritePin(LTE_RESET_GPIO_Port, LTE_RESET_Pin, GPIO_PIN_SET);

    LTE_SendAT("AT");

    while (1) {
        HAL_GPIO_TogglePin(STATUS_LED_GPIO_Port, STATUS_LED_Pin);
        uint16_t adc = Read_ACS712_ADC();
        char msg[64];
        snprintf(msg, sizeof(msg), "ACS712 ADC=%u\r\n", adc);
        HAL_UART_Transmit(&huart1, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
        HAL_Delay(1000);
    }
}

• Add final DS18B20 and DHT22 protocol drivers.
• Add OLED driver once the display controller is selected.
• Confirm LTE AT-command baud rate for the exact A7672S firmware.