Library for Unit RTC and the built-in RX8130CE RTC using M5UnitUnified.
M5UnitUnified is a library for unified handling of various M5 units products.
Unit RTC is a programmable real-time clock module that integrates the HYM8563 low-power CMOS real-time clock/calendar chip. It uses the I2C communication interface (address 0x51). This library also supports the compatible BM8563 / PCF8563 (UnitPCF8563).
The Epson RX8130CE real-time clock built into M5Stack boards such as Tab5 (UnitRX8130, on the internal I2C bus, address 0x32).
On Tab5 use Tab5BuiltinRTC (a UnitRX8130 subclass). The interrupt output of the RX8130CE drives the power controller of
Tab5, and a periodic timer interrupt left enabled can make it unbootable. Tab5BuiltinRTC refuses the timer and the
update interrupts (as M5Unified does on Tab5) and charges the backup supercapacitor by default.
Charging of the backup battery (config_t::charge) is off by default. Turn it on only when a rechargeable battery or a
supercapacitor is on VBAT (e.g. Tab5, StampPLC). Never turn it on with a primary cell (e.g. the CR2032 of ToughC5).
writeAlarm() / writeTimer() do not enable the interrupt output (AIE / TIE): the flags are polled by update().
Enable it with writeAlarmInterrupt() / writeTimerInterrupt() (and writeUpdateInterrupt() of UnitRX8130) when
the interrupt pin is used.
The M5Unified compatible setAlarmIRQ() / setTimerIRQ() enable it, as M5Unified does.
#include <M5UnitUnifiedRTC.h> // For UnitUnifiedSee also examples/UnitUnified
- UnitRTC/NTPSync: Gets the time from NTP over Wi-Fi and sets the RTC. It can also use the built-in RX8130CE of Tab5 (see below)
- UnitRTC/AlarmNotify: Sets an alarm one minute ahead and notifies when it fires. It can also use the built-in RX8130CE of Tab5
- UnitRTC/PeriodicTimer: Fires the countdown timer periodically. It can also use the built-in RX8130CE of Tab5
- UnitRTC/ViaPaHub: Reads the date and time through PaHub (ch:0). Requires M5Unit-HUB.
NTPSync / AlarmNotify / PeriodicTimer work with Unit RTC by default. To use the built-in RX8130CE of Tab5, choose the
define symbol in the source of the example (e.g. examples/UnitUnified/UnitRTC/NTPSync/main/NTPSync.cpp).
// *************************************************************
// Choose one define symbol to match the RTC you are using
// *************************************************************
#if !defined(USING_UNIT_RTC) && !defined(BUILTIN_UNIT_RX8130)
// For Unit RTC (U126)
#define USING_UNIT_RTC
// For Tab5 (C145) built-in RX8130CE (internal I2C)
// #define BUILTIN_UNIT_RX8130
#endifNTPSync takes the Wi-Fi credentials from EXAMPLE_SSID / EXAMPLE_PASSWORD. Fill in the defines in
examples/UnitUnified/UnitRTC/NTPSync/main/NTPSync.cpp, or give them as compile options
(-DEXAMPLE_SSID="\"YOUR_SSID\"" -DEXAMPLE_PASSWORD="\"PASSWORD\"").
With an empty SSID, the config stored in NVS by an earlier connection is used.
AlarmNotify / PeriodicTimer poll the flags with update() and do not enable the interrupt output, so they can run with
the built-in RX8130CE of Tab5 (BUILTIN_UNIT_RX8130, which uses Tab5BuiltinRTC).
NOTE: The ESP-IDF native build (
idf.py) targets ESP-IDF 5.1 or later (5.x and 6.x). The legacy library (Unit_RTC.h) is for Arduino only and is not built under ESP-IDF.
On ESP-IDF native builds (idf.py), the RTC of NTPSync / AlarmNotify / PeriodicTimer is selected via Kconfig instead
of editing the source #define: idf.py menuconfig → M5Unit-RTC example → Target RTC.
The M5Tab5 built-in RX8130CE option appears only when the target is esp32p4.
The Wi-Fi credentials of NTPSync are set in NTPSync settings. ViaPaHub needs no Kconfig choice. Build them directly:
cd examples/UnitUnified/UnitRTC/PeriodicTimer
idf.py set-target esp32s3 # or esp32 / esp32c5 / esp32c6 / esp32h2 / esp32p4 / ...
idf.py build flash monitorNTPSync uses Wi-Fi, so it does not support ESP32-H2 (NanoH2). On ESP32-P4 (Tab5) the Wi-Fi runs on the ESP32-C6 co-processor (esp_hosted), which needs ESP-IDF 5.3 or later.
Support via PaHub
| Unit | Support | Note |
|---|---|---|
| UnitRTC | OK |
See also the ViaPaHub example and M5Unit-HUB
If you want to generate documents on your local machine, execute the following command
bash docs/doxy.sh
It will output it under docs/html
If you want to output Git commit hashes to html, do it for the git cloned folder.
The legacy library (Unit_RTC) is a standalone Arduino driver for Unit RTC that does not depend on M5UnitUnified.
When using M5UnitUnified, do not use it at the same time as the legacy library.
#include <Unit_RTC.h>