Edgi-Talk_RTC Example Project

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Introduction

This example project runs on the M33 core with RT-Thread RTOS, demonstrating the RTC (Real-Time Clock) functionality. It allows users to quickly learn how to set, read, and print RTC time, providing a reference for time management and periodic tasks in embedded systems.

RTC Overview

1. Overview

RTC (Real-Time Clock) is an electronic module or chip that keeps track of actual time (year, month, day, hour, minute, second). It can be integrated in an MCU or exist as an external chip, providing system time, alarm triggers, and timed event functions.

RTC is low-power and stable, continuing to operate even when the main power is off, using backup power such as a battery or supercapacitor.

2. Working Principle

RTC consists of a low-power oscillator + counter:

1. Clock source

   • Typically uses a 32.768 kHz crystal, providing a stable time base.

2. Frequency division

   • Divides the crystal signal to produce a 1 Hz second pulse.

   • Counts seconds to generate minutes, hours, days, months, and years.

3. Registers

   • Internal registers store current time, date, alarms, etc.

4. Power backup

   • Battery or supercapacitor maintains RTC operation during main power loss.

3. RTC Types

• Internal RTC

  • Integrated inside MCU.

  • Pros: lower cost, fewer components.

  • Cons: crystal accuracy affected by PCB and temperature.

• External RTC

  • Standalone chips, e.g., DS3231, PCF8563.

  • Pros: high accuracy, I²C/SPI interface.

  • Cons: increases PCB space and cost.

4. Key Parameters

Parameter	Description
Oscillator	Typically 32.768 kHz, low-power and stable
Accuracy	ppm / seconds per day, affects drift
Supply voltage	1.8~5V, supports backup power
Power consumption	1~5 µA (low-power mode)
Interface type	I²C, SPI, or internal MCU bus
Extended functions	Alarm, square wave, temperature compensation, timed wakeup

5. RTC Functions

• Real-time clock: provides current time and date.

6. Applications

• Embedded devices: time tracking and event logging.

• Low-power IoT: periodic wake-up for data collection.

• Wearables: precise timing for watches or fitness devices.

• Data loggers & industrial control: timestamps and logs.

• Automotive electronics: dashboard timing, recorders, infotainment.

Software Description

• Developed on the Edgi-Talk platform.

• Example features:

  • Initialize RTC device

  • Set date and time

  • Delay and read current time

  • Export RTC functions as rtc_sample msh command

• The structure clearly demonstrates RTC driver usage on M33 core.

Usage

Build and Download

1. Open the project and compile it.

2. Connect the board USB to your PC via DAP.

3. Flash the compiled firmware.

Running Result

• After powering on, open the serial terminal and run:

rtc_sample

• The system performs:

  1. Initialize RTC device

  2. Set date to 2025-07-01

  3. Set time to 23:59:50

  4. Print current time

  5. Delay 3 seconds

  6. Print time again

• Example output:

Tue Jul  1 23:59:50 2025
Tue Jul  1 23:59:53 2025

Notes

• Ensure RTC is properly connected and recognized by the system.

• To modify the graphical configuration:

tools/device-configurator/device-configurator.exe
libs/TARGET_APP_KIT_PSE84_EVAL_EPC2/config/design.modus

• Save changes and regenerate code after editing.

Startup Sequence

+------------------+
|   Secure M33     |
|  (Secure Core)   |
+------------------+
          |
          v
+------------------+
|       M33        |
| (Non-Secure Core)|
+------------------+
          |
          v
+-------------------+
|       M55         |
| (Application Core)|
+-------------------+

⚠️ Follow this flashing order strictly; otherwise, the system may not operate correctly.

• If the example does not run, first compile and flash Edgi-Talk_M33_S_Template to ensure core initialization.

• To enable M55, open:

RT-Thread Settings --> Hardware --> select SOC Multi Core Mode --> Enable CM55 Core