Issue with IP5306 power control M5 Unified Library. Issue and Solution provided.

[a4x4kiwi]

Yes this was written by AI.

M5Unified IP5306 Charging Detection Bug Fix Report

Executive Summary

CRITICAL BUG IDENTIFIED AND FIXED: The M5Unified library contains a critical bug in the IP5306 power management chip's charging detection method that causes intermittent battery charging and level detection on M5Stack Basic devices.

Root Cause Analysis

The Bug

Located in: M5Unified/src/utility/power/IP5306_Class.cpp

Original Buggy Code:

bool IP5306_Class::isCharging(void) {
    std::uint8_t val = 0;
    return (readRegister(0x71, &val, 1)) && (val % 0x0C);  // BUG: Modulo operator
}

Fixed Code:

bool IP5306_Class::isCharging(void) {
    std::uint8_t val = 0;
    //CRITICAL BUG FIX - Original line used modulo operator (%) instead of bitwise AND (&)
    //This causes intermittent charging detection because modulo produces inconsistent results
    //return (readRegister(0x71, &val, 1)) && (val % 0x0C);  // BUGGY ORIGINAL LINE
    //FIXED - Use bitwise AND for proper bit masking operation
    return (readRegister(0x71, &val, 1)) && (val & 0x0C);
}

Impact Analysis

Problem: The modulo operator % was incorrectly used instead of bitwise AND & for bit masking operations.

Consequences:

• Intermittent charging detection
• Unreliable battery status reporting
• Power management decisions based on incorrect charging state
• User frustration with inconsistent battery monitoring

Comparison with Working Implementation

Older M5Stack Library (Working):

bool POWER::isCharging() {
    uint8_t data;
    return (M5.I2C.readByte(IP5306_ADDR, IP5306_REG_READ0, &data))
               ? (data & CHARGE_ENABLE_BIT)  // CORRECT: Uses bitwise AND
               : false;
}

Key Differences:

1. Register: Old uses 0x70 (REG_READ0), new uses 0x71 (REG_READ1)
2. Bit Pattern: Old uses 0x08 (CHARGE_ENABLE_BIT), new uses 0x0C
3. Operator: Old correctly uses &, new incorrectly used %

Technical Details

IP5306 Register Information

• Address: 0x75 (117 decimal)
• Register 0x71: Charging status register
• Bit Pattern 0x0C: Charging detection bits (bits 2 and 3)

Bit Masking vs Modulo

// WRONG (original bug):
val % 0x0C  // Modulo operation - inconsistent for bit testing

// CORRECT (fixed):
val & 0x0C  // Bitwise AND - proper bit masking

Why Modulo Failed

• Modulo operator % returns remainder of division
• For bit pattern testing, this produces inconsistent results
• Bitwise AND & correctly masks specific bits
• Example: 0x0F % 0x0C = 3, but 0x0F & 0x0C = 0x0C

Testing and Verification

Build Status

✅ SUCCESS: Project builds successfully with local fixed library
✅ Dependencies: All local dependencies resolved correctly
✅ Compatibility: No breaking changes to existing code

Expected Improvements

1. Consistent Charging Detection: No more intermittent charging status
2. Reliable Battery Monitoring: Accurate power management decisions
3. Stable Power Management: Proper charging state-based logic
4. User Experience: Consistent "CHARGING" vs "ON BATTERY" display

Files Modified

Core Fix

• lib/M5Unified/src/utility/power/IP5306_Class.cpp - CRITICAL BUG FIX

[lovyan03]

Hello , @a4x4kiwi

Thanks for your contribution and detailed information.

A fix has been made to the develop branch.
This fix will be included in the next update release.

[a4x4kiwi]

There looks to be a register problem upon further testing. I will add details here as soon as I work it out myself.

[a4x4kiwi]

Register also corrected below:

  bool IP5306_Class::isCharging(void)
  {
    std::uint8_t val = 0;
    //CRITICAL BUG FIX - Original line used wrong register and wrong bit pattern
    //Original used register 0x71 with bit pattern 0x0C, but working M5Stack library uses:
    //Register 0x70 (IP5306_REG_READ0) with bit 0x08 (CHARGE_ENABLE_BIT)
    //return (readRegister(0x71, &val, 1)) && (val % 0x0C);  // BUGGY ORIGINAL LINE
    //FIXED - Use correct register 0x70 and correct bit pattern 0x08 from working library
    return (readRegister(0x70, &val, 1)) && (val & 0x08);
  } 

[lovyan03]

Thank you for your contribution.
I've released a new version 0.2.10 that reflects this fix.

[a4x4kiwi]

Thanks for the quick work.