IP5306 Power Management IC

The IP5306 is a fully integrated power bank system-on-chip with a 2.4A charger and a 2A discharger. This chip—or one of its many Chinese clones, like the FM5324GA—is commonly used in modern DIY modules.

For highly integrated chips like this one, it is essential to understand their concepts and functionality before use. Some of its features - like its optional torch mode - may not be immediately apparent and could lead to unintended risks.

Overview

The IP5306 is found on affordable breakout boards like the X-150 and the MH-CD42.

Modules utilizing this chip are highly compact (typically 15-20x25mm) yet surprisingly powerful. With a single Li-Ion cell, they can deliver up to 2A at 5V.

This compactness is made possible by a clever architecture that uses a single inductor for both charging and discharging operations.

Use Cases

This chip is ideal for adding battery power to external 5V devices such as microcontrollers, WS2812 LED strips, DIY flashlights, and more. It is also suitable for building simple power banks.

Permanently Connected Devices

This chip is especially suited for adding battery support to 5V devices:

• a push button can be used to control power to the connected device, so it can be turned on and off as needed.
• Only the device connected to the power output can draw energy from the battery.
• The power input is exclusively reserved for charging the battery and does not allow external devices to deplete the battery.

Power Bank

When designing a power bank, the goal is to provide power on demand to various USB devices. To achieve this, you can add one or more USB connectors (of your chosen type) to the chip’s power output.

Key considerations for power bank design with this chip:

• The chip provides a fixed 5V output voltage only. This limitation is a direct consequence of the chip targeting 1S batteries (single-cell configurations).
• Boosting the voltage beyond 5V would require higher battery currents, larger physical components (e.g., coils), and lead to inefficiencies.

As a result:

• This chip does not support quick charge protocols, which rely on multiple output voltages such as 9/12/15/20V.
• Devices connected to the power bank will charge at standard speeds, limited to a fixed 5V output at a maximum current of 2A (10W).

In a nutshell, this chip is excellent for building physically very small power banks.

No Temperature Sensor

The IP5306 features several built-in protection mechanisms, including over-temperature protection, but there is no support for external temperature sensors.

External temperature sensors can detect catastrophic battery failures during charging.

Such sensors, though, are more commonly integrated into power management chips designed for higher-capacity battery systems, where the risk of thermal issues is higher due to larger energy storage and discharge rates.

Battery Requirements

The IP5306 supports 1S battery configurations (Li-Ion and Li-Po). You can use a single cell or connect multiple cells in parallel to increase capacity while maintaining the required 1S voltage.

Battery Voltage

This chip is designed for Li-Ion and Li-Po batteries with a maximum voltage of 4.2V. It also includes optional support for high-voltage cells with a maximum voltage of 4.35V. However, LiFePO₄ batteries are incompatible, and using them can be hazardous.

Some users have reported that the 4.35V setting is ineffective, with the maximum charging voltage remaining at 4.2V. Batteries must explicitly support 4.35V to utilize this setting. Many standard Li-Ion batteries with built-in BMS will cut off power above 4.2V. Additionally, their internal resistance increases sharply beyond this voltage, causing the charging current to taper naturally. To use the 4.35V setting, ensure your batteries are specifically designed for 4.35V operation.

Selecting Appropriate Battery Capacity

Given the high performance of the IP5306, selecting a suitable battery is critical. Batteries that are too small can lead to overcharging and/or over-discharging, increasing the risk of fire hazards.

Generally, you will need a battery with a minimum capacity of around 3,500mAh.

Key Considerations:

• High Charging Current:
  The charging current is fixed at 2.4A. At a 1C charge rate, the battery must have a capacity of at least 2,400mAh to safely handle this current.

• High Power Output:
  The chip can supply up to 10W to its power output. When the battery voltage drops to 3V near depletion, a 10W output at 90% conversion efficiency requires approximately 3.5A. At a 1C discharge rate, the battery must have a capacity of at least 3,500mAh.

• Minimum Capacity:
  Due to the fixed charging current, at 1C charge rate, your battery must have a capacity of at least 2.400mAh. Assuming a 1C discharge rate as well, at this capacity the battery could deliver a maximum output current of 2.4A. When the battery is close to depletion at 3V, this allows for a maximum of 6.5W power output (1.3A at 5V output).
• Recommended Minimum Capacity:
  To take advantage of the maximum 2A output (10W) that this chip supports, your battery capacity must be at least 3.500mAh at an assumed 1C discharge rate.

If the chip stops charging after only a few minutes and reports the battery as fully charged when it is not, this might indicate that the battery is too small for the 2.4A charging current. Overcharging a small battery can cause its voltage to temporarily rise too quickly, triggering the chip’s early cut-off protection.

Charging

Charging and discharging are separate features, and you can use the IP5306 for charging only, possibly as a replacement for a simple TP4056, simply to achieve higher charging currents.

The chip lacks battery reverse polarity protection. Use an ideal diode or other suitable protection if reverse polarity is a risk, i.e. because you are using battery holders where a user could be intreagued to insert a battery in wrong position.

Initiating Charging

Charging starts automatically when a power supply is connected, and the battery voltage is >2.8V and <4.2V. The external power supply must provide 5V at 2A minimum.

During charging, the indicator LED show charging progress in 25% increments, and one LED is blinking at 1Hz.

Charging phases:

1. Deep Discharge Recovery: If battery voltage is below 2.8V, the chip supplies 180mA until safe voltage levels are reached.
2. Constant Current: For voltage between 2.8V and the cut-off, the chip charges at 2.4A.
3. Constant Voltage: Once the battery reaches 4.2V, current tapers off until it falls below 100mA or 24 hours elapse.

Once charging has completed, all four indicator LEDs light solidly.

A new charging cycle is initiated automatically once the battery voltage drops below 4.1V.

When a battery has accidentally been deeply discharged (i.e. by keeping it in storage for too long so that normal self-discharge could cause a voltage drop below 2.8V), it can no longer absorb the normal amount of energy. Charging such a battery with a normal charge current would convert the excess energy into heat and might cause a fire or explosion. The recovery charge mode is taking this into account. Whether or not it will be successful in recovering such a battery is not certain. However, if the battery isn’t fully charged after a maximum of 24 hours, the charging cycle is aborted.

Supplying Power

The chip includes a robust and efficient boost converter capable of supplying 5V at up to 2A. It is equipped with over-current and short circuit protection mechanisms.

When a load is connected to the power output, the boost converter activates and begins supplying power. When the load is removed (or the load drops below 45mA for more than 32s), the boost converter automatically shuts down to conserve battery power.

While power is being supplied, four LEDs indicate the battery’s state of charge in 25% increments. Each LED is supplied with 4mA.

When the battery’s state of charge drops below 3%, one LED will blink at 2Hz to alert the user. If the battery voltage falls further, below 2.8-2.9V, the over-discharge protection feature turns off the power output to prevent damage to the battery.

Automatic Load Detection

The automatic load detection feature is essential for preserving battery life.

Operating the boost converter requires approximately 100µA. If the boost converter remained active continuously—even without an active load—it could deplete the battery unnecessarily.

To address this, both the boost converter and the indicator LEDs are activated only when required. In inactive states, the chip minimizes power consumption, reducing quiescent current to 30-50µA.

Two operational modes manage this behavior:

The chip automatically transitions between these modes:

• Load Detection: The chip continuously monitors the power output. When it detects a load, it activates Standby Mode to supply power to the connected device.
• Load Removal Detection: If the load drops below 45mA for a continuous period of at least 32 seconds, the chip shuts off the boost converter and switches to Off Mode.

A user once reported that the chip worked properly but stopped after exactly 33 seconds. This behavior was due to the automatic load removal detection. The user’s load was too small to sustain Standby Mode. To prevent this, you can increase the load above 45mA (e.g., by adding a small LED or resistor). Alternatively, you can enable the power output manually using the push button connector in regular intervals to reset the load removal timer (see below).

Automatic Power-off

The chip automatically cuts off power in the following scenarios (when operating on battery power):

• Low Load: If the load drops below 45mA for at least 32 seconds, the chip assumes the load is disconnected and turns off the boost converter.
• High Load: If the load exceeds 4A, the chip performs an emergency shutdown within 200µs to prevent damage.
• Battery Empty: If the battery voltage falls below 2.8-2.9V, the chip disables the boost converter to protect the battery from over-discharge.
• Manual: Using a push button signal (see below), the chip turns off the boost converter, even with the load still connected. This is useful for turning off permanently connected devices.

While charging, the output is always active.

Push Button Support

An optional push button can be connected to the K and GND solder pads on most boards. While not mandatory, it allows manual control over power output and can access a special “torch mode”.

Always use a resistor in series with the push button to limit potential current flow:

• In some chip configurations, an optional flashlight function may be present. In this setup, an LED is connected in parallel with the push button. Pressing the button in such configurations effectively short-circuits the LED, which can result in high currents. These currents may damage the button, the LED, or the board itself.

• To prevent such issues, use a resistor with a value of 2kΩ or 10kΩ in series with the button. Some chips can actively differentiate between these two resistor values. Depending on the resistance used, the chip may either activate or deactivate the flashlight function.

A user reported that pressing the push button produced a cloud of smoke. It turned out this user had taken two breakout boards and connected both push button wires to one push button to control both boards at the same time. While this is perfectly ok to do, the user did not add 10kΩ resistors. So when the push button was pressed, a temporary short circuit occured in both boards, resulting in high currents flowing across the push button. Since DIY push buttons typically are for logic levels only, they can easily burn up when exposed to such high currents. You now know that with this board, it is crucial to limit current flow with at least a 2kΩ resistor.

Types of Button Presses

All chip variants distinguish three fundamental key press patterns:

• Short press: >30ms but <=2s
• 2x Short press
• Long press: >2s

Manually Control Output Power

A short press (>30ms impulse) enables power output in all chip variants. Use a short press to turn on a device, or to reset the load removal detection timer before it can kick in on light loads <45mA.

With low loads (<50mA), your logic could send an impulse (<30ms <2s, simulated short press) in <30s intervals to prevent unintentional power off.

Manually turning off the boost converter varies between chip variants. With the original IP5306, this requires a long press, whereas clones like the FM5324GA may require two short presses instead.

Button presses only control the internal boost converter. The power output remains always active when the chip is connected to an external power supply (i.e., during charging).

Torch Mode

A less commonly noticed feature of this chip is its ability to support an external flashlight LED. When present, the LED is connected in parallel with the push button.

This torch mode is the reason why the push button must always be used with a 2kΩ or 10kΩ resistor in series. Without this resistor, activating the torch mode—either intentionally or accidentally—can result in large currents, as pressing the push button would effectively short-circuit the flashlight LED.

On certain chip models, the torch mode may either be permanently disabled or configurable by using a 2kΩ resistor instead of a 10kΩ in series with the push button.

Keep in mind that chips are often manufactured to meet specific customer requirements. If your chip has a different marking, it may function similarly to the IP5306 but exhibit slight variations, such as different push button actions or modified indicator LED behavior.

Issues

Here are the top issues with this chip and the boards that are using it:

• User Errors:
  • Battery: when you add a battery that is too small and cannot handle the high charge and discharge currents, charging the battery may not work, and there is a fire hazard.
  • Push Button: when you add a push button and omit a 10kΩ series resistor, when you press the button, high currents can flow and damage the button.
• Design Issues:
  • Load Removal Discovery: with small loads <50mA, the unit cuts power after 32s. This is by design. To work around this, you can have your microcontroller ground the push button key (via a 10kΩ resistor, or you might ruin your microcontroller) in intervals of <30s. This resets the load removal discovery timer. Make sure you ground the pin for at least 50ms in order to be considered a short press. Alternatively, you can keep the pin permanently to ground as described below.
  • Various Chip Variants: the fact that boards are produced with a variety of generic and cloned chips instead of the original IP5306 can cause issues due to slight variations in behavior.

  • Wake-Up Issues: there are reports with boards using the FM5324GA, that after prolonged operation for 24-48hrs, the board may not automatically wake up from standby anymore when a new load is connected.

    The reason is not yet clear. A remidy is to manually short press the push button or cause a reset of power paths by supplying a charging power. You might be able to work around this by keeping the chip active all the time (preventing Off mode) at the expense of a slightly higher quiescent power consumption via the following circuit (which may also help with continuously operating low loads <50mA):

Keeping Power Output Active

One of the top design issues is the load removal detection that kicks in once the load drops below <50mA for more than 32s.

Whether you want to work around this load removal detection, or whether you want to generally prevent the board from entering Off mode, i.e. to work around wake-up problems, here are two suggestions you may want to try (at own risk) to keep the power output active:

• MH-CD42 breakout board:

  

• X-150 breakout board:

  

By keeping the boards’ boost converter active all the time, this will increase quiescent current consumption by approximately 50uA.

As always on this site, use all information including suggested circuitry entirely at your own risk.

I2C Configuration

Specific versions of the IP5306 may behave differently and can have additional features, most notably an I2C interface for advanced configuration. Please note that most “normal” breakout boards use the default IP5306 which has no I2C interface.

The following applies only to IP5306 chips with enabled I2C interface:

I2C Settings

Registers

Here is a list of registers accessible via I2C on IP5306 chips with enabled I2C interface:

REG_SYS_0: 0x00 Input/Output Enable

Auto Power On When Load Connected, when enabled, automatically detects a connected load. This very same feature is also responsible for automatically turning off the output once the load is removed. This includes the light load detection: once the load drops below 50mA for the time configured in REG_SYS_2 (0x02, normally 32 seconds), the outout is also automatically turned off.

This may be undesirable: when you supply light loads (i.e. microcontrollers in sleep mode), the IP5306 may unexpectedly turn off the power supply.

In order to disable light load detection and ensure that the IP5306 supplies power all the time, turn off Auto Power On When Load Connected by setting its bit to 0.

As a consequence, IP5306 no longer automatically turns on its output once power is drawn, and it never turns off power automatically anymore, even if no power at all is drawn. You now control the power output entirely manually via the control button.

REG_SYS_1: 0x01 Buttons

REG_SYS_2: 0x02 Light Load Shutdown

REG_CHG_0: 0x020 Stop Charging

REG_CHG_1: 0x021 Stop Charging

REG_CHG_2: 0x22 Battery Adjustment

REG_CHG_3: 0x23 Constant Current Charging

REG_CHG_4: 0x24 Charging Current

REG_READ_0: 0x70 Charging Status

REG_READ_1: 0x71 Charging Status

REG_READ_2: 0x72 Charging Status

REG_READ_3: 0x77 Key Press Detection

REG_READ_4: 0x78 LED Indicator

I2C Libraries

If you want to read and write configuration data via I2C, you need to know:

• I2C Register: what is the number of the register that holds the required information?
• Bit(s): which bit(s) store the desired information? There can be other bits in the same register that control other things.
• Meaning: how are the bit values actually interpreted? So what does a 0 or 1 in a bit actually stand for, or do?

Libraries can help you very much as they do much of this work for you, and provide simple-to-use functions.

Keep in mind that in order to successfully use any of these libraries, you need to physically correctly wire up the IP5306 breakout board to your microcontroller, and your breakout board must be using a I2C-enabled IP5306. Many cheap boards use IP5306 variants without I2C interface (as it is not needed). In this case, you cannot use I2C, and below libraries won’t help you.

Basic IP5306 I2C Control Library (Example #2)

IP5306-arduino is a very simple yet very efficient library that works for a large range of microcontrollers. It provides a range of functions covering all controllable I2C features:

uint8_t IP5306_GetKeyOffEnabled() 
uint8_t IP5306_SetKeyOffEnabled(uint8_t value)                //0:dis,*1:en
uint8_t IP5306_GetBoostOutputEnabled()         
uint8_t IP5306_SetBoostOutputEnabled(uint8_t value)           //*0:dis,1:en
uint8_t IP5306_GetPowerOnLoadEnabled()          
uint8_t IP5306_SetPowerOnLoadEnabled(uint8_t value)           //0:dis,*1:en
uint8_t IP5306_GetChargerEnabled()      
uint8_t IP5306_SetChargerEnabled(uint8_t value)               //0:dis,*1:en
uint8_t IP5306_GetBoostEnabled()          
uint8_t IP5306_SetBoostEnabled(uint8_t value)                 //0:dis,*1:en
uint8_t IP5306_GetLowBatShutdownEnable()        
uint8_t IP5306_SetLowBatShutdownEnable(uint8_t value)         //0:dis,*1:en
uint8_t IP5306_GetBoostAfterVin()             
uint8_t IP5306_SetBoostAfterVin(uint8_t value)                //0:Closed, *1:Open
uint8_t IP5306_GetShortPressBoostSwitchEnable() 
uint8_t IP5306_SetShortPressBoostSwitchEnable(uint8_t value)  //*0:disabled, 1:enabled
uint8_t IP5306_GetFlashlightClicks()          
uint8_t IP5306_SetFlashlightClicks(uint8_t value)             //*0:short press twice, 1:long press
uint8_t IP5306_GetBoostOffClicks()              
uint8_t IP5306_SetBoostOffClicks(uint8_t value)               //*0:long press, 1:short press twice
uint8_t IP5306_GetLightLoadShutdownTime()    
uint8_t IP5306_SetLightLoadShutdownTime(uint8_t value)        //0:8s, *1:32s, 2:16s, 3:64s
uint8_t IP5306_GetLongPressTime()              
uint8_t IP5306_SetLongPressTime(uint8_t value)                //*0:2s, 1:3s
uint8_t IP5306_GetChargingFullStopVoltage()     
uint8_t IP5306_SetChargingFullStopVoltage(uint8_t value)      //0:4.14V, *1:4.17V, 2:4.185V, 3:4.2V (values are for charge voltage 4.2V, 0 or 1 is recommended)
uint8_t IP5306_GetChargeUnderVoltageLoop()                    //Automatically adjust the charging current when the voltage is greater than the set value
uint8_t IP5306_SetChargeUnderVoltageLoop(uint8_t value)       //Vout=4.45V + (v * 0.05V) (default 4.55V) //When charging maximum current, the charge is less than the set value. Slowly reducing the charging current to maintain this voltage
uint8_t IP5306_GetEndChargeCurrentDetection() 
uint8_t IP5306_SetEndChargeCurrentDetection(uint8_t value)    //0:200mA, 1:400mA, *2:500mA, 3:600mA
uint8_t IP5306_GetVoltagePressure()            
uint8_t IP5306_SetVoltagePressure(uint8_t value)              //0:none, 1:14mV, *2:28mV, 3:42mV (28mV recommended for 4.2V)
uint8_t IP5306_GetChargeCutoffVoltage()        
uint8_t IP5306_SetChargeCutoffVoltage(uint8_t value)          //*0:4.2V, 1:4.3V, 2:4.35V, 3:4.4V
uint8_t IP5306_GetChargeCCLoop()               
uint8_t IP5306_SetChargeCCLoop(uint8_t value)                 //0:BAT, *1:VIN
uint8_t IP5306_GetVinCurrent()                              
uint8_t IP5306_SetVinCurrent(uint8_t value)                   //ImA=(v*100)+50 (default 2250mA)
uint8_t IP5306_GetShortPressDetected()                      
uint8_t IP5306_ClearShortPressDetected()                    
uint8_t IP5306_GetLongPressDetected()                     
uint8_t IP5306_ClearLongPressDetected()                   
uint8_t IP5306_GetDoubleClickDetected()                     
uint8_t IP5306_ClearDoubleClickDetected()                   
uint8_t IP5306_GetPowerSource()                               //0:BAT, 1:VIN
uint8_t IP5306_GetBatteryFull()                               //0:CHG/DIS, 1:FULL
uint8_t IP5306_GetLevelLeds()                                 //LED[0-4] State (inverted)
uint8_t IP5306_GetOutputLoad()                                //0:heavy, 1:light

This library is so small that you could in fact incorporate the code into your own source code. Here is what the library does:

Helpers

The library comes with four helpers:

• I2C Registers: it defines the available I2C registers for you:

  #define IP5306_REG_SYS_0    0x00
  #define IP5306_REG_SYS_1    0x01
  #define IP5306_REG_SYS_2    0x02
  #define IP5306_REG_CHG_0    0x20
  #define IP5306_REG_CHG_1    0x21
  #define IP5306_REG_CHG_2    0x22
  #define IP5306_REG_CHG_3    0x23
  #define IP5306_REG_CHG_4    0x24
  #define IP5306_REG_READ_0   0x70
  #define IP5306_REG_READ_1   0x71
  #define IP5306_REG_READ_2   0x72
  #define IP5306_REG_READ_3   0x77
  #define IP5306_REG_READ_4   0x78
  

• Bit Banging: it defines two mathematical helper functions that help you extract bits from a byte, and changing bits in an existing byte:

  uint8_t ip5306_get_bits(uint8_t reg, uint8_t index, uint8_t bits) {
      int value = ip5306_get_reg(reg);
      if(value < 0) {
        return 0;
      }
      return (value >> index) & ((1 << bits)-1);
  }
  
  void ip5306_set_bits(uint8_t reg, uint8_t index, uint8_t bits, uint8_t value) {
      uint8_t mask = (1 << bits) - 1;
      int v = ip5306_get_reg(reg);
      if(v < 0) {
          //Serial.printf("ip5306_get_reg fail: 0x%02x\n", reg);
          return;
      }
      v &= ~(mask << index);
      v |= ((value & mask) << index);
        if(ip5306_set_reg(reg, v)) {
      }
  }
  

• I2C Read/Write: it defines two generic functions to read or write a byte to an I2C register:

  int ip5306_get_reg(uint8_t reg){
      Wire.beginTransmission(0x75);
      Wire.write(reg);
      if(Wire.endTransmission(false) == 0 && Wire.requestFrom(0x75, 1)){
          return Wire.read();
      }
      return -1;
  }
  
  int ip5306_set_reg(uint8_t reg, uint8_t value){
      Wire.beginTransmission(0x75);
      Wire.write(reg);
      Wire.write(value);
      if(Wire.endTransmission(true) == 0){
          return 0;
      }
      return -1;
  }
  

Specific I2C Functions

With the three helpers from above, it then defines all specific functions that you can use to control the IP5306 in the header file, like this one:

#define IP5306_GetKeyOffEnabled()               ip5306_get_bits(IP5306_REG_SYS_0, 0, 1)

Here is how this works:

• The function IP5306_GetKeyOffEnabled() is actually calling the generic ip5306_get_bits()
• It is asking to return one bit (1) from index position 0 (0) of register 0x00 (IP5306_REG_SYS_0).
• According to the IP5306 register map, bit 0 controls Button Shutdown Enable:

What exactly Button Shutdown Enable does is often not well documented, even if you dig through the official I2C Register Map, and requires some guessing and experimenting. In this particular case, Button Shutdown Enable controls whether the button that can be connected to the IP5306 can serve to manually turn off the power output, typically by double pressing it. IP5306_GetBoostOffClicks() and IP5306_SetBoostOffClicks() coincidentally control whether shutting off the power is controlled by a double-click or a long press.

As you see, the way this library is organized is working well but requires intimate knowledge of the bit definitions and their meaning. Prepare to keep the I2C Register Map open in parallel, especially when you deal with configuration items that use more than one bit.

For example, IP5306_SetLightLoadShutdownTime() can set the timeout after which the IP5306 shuts off when a load <50mA is connected:

#define IP5306_SetLightLoadShutdownTime(v)      ip5306_set_bits(IP5306_REG_SYS_2, 2, 2, v)//0:8s, *1:32s, 2:16s, 3:64s

This setting is controlled by two bits, and the comment explains the bits:

You just need to know what the expected values are. The function calls ip5306_set_bits() with the appropriate arguments. In this particular case, two bits (2) need to be written to I2C register 0x02 (IP5306_REG_SYS_2) starting at index position 2 ( 2). Again, you can look up the details for this I2C register and its bits and definitons.

Sophisticated IP5306 I2C Library

IP5306_I2C does basically what the previous library did, however this author has also typed many of the arguments and return values.

So instead of having to guess what a specific bit actually means, you find structs (self-defined structured records).

Here is the list of functions this library provides:

void boost_mode(uint8_t boost_en);
void charger_mode(uint8_t charger_en);
void power_on_load(uint8_t power_on_en);
void boost_output(uint8_t output_val);
void button_shutdown(uint8_t shutdown_val);

void boost_ctrl_signal(uint8_t press_val);
void flashlight_ctrl_signal(uint8_t press_val);
void short_press_boost(uint8_t boost_en);
void boost_after_vin(uint8_t val);
void low_battery_shutdown(uint8_t shutdown_en);

void set_long_press_time(uint8_t press_time_val);
void set_light_load_shutdown_time(uint8_t shutdown_time);

void set_charging_stop_voltage(uint8_t voltage_val);
void end_charge_current(uint8_t current_val);
void charger_under_voltage(uint8_t voltage_val);

void set_battery_voltage(uint8_t voltage_val);
void set_voltage_pressure(uint8_t voltage_val);
void set_cc_loop(uint8_t current_val);

uint8_t check_charging_status(void);
uint8_t check_battery_status(void);
uint8_t check_load_level(void);
uint8_t short_press_detect(void);
uint8_t long_press_detect(void);
uint8_t double_press_detect(void);

When you look at the function signatures and compare them with the previous library, you’ll see that function arguments are typed. The previous library used uint8_t for all arguments, and you had to know the appropriate byte values (and bit-bang the appropriate bits).

Let’s take a closer look what is different in this library:

Easier Handling

Instead of using just bytes for everything, this library defines structs (structured data records) per I2C register. Here is an example for 0x00:

/*SYS_CTL0*/
union{
    struct{
     uint8_t BUTTON_SHUTDOWN             : 1;
     uint8_t SET_BOOST_OUTPUT_ENABLE     : 1;
     uint8_t POWER_ON_LOAD               : 1;
     uint8_t RSVD                        : 1;
     uint8_t CHARGER_ENABLE              : 1;
     uint8_t BOOST_ENABLE                : 1;
     uint8_t RSVD2                       : 2;
       
    }bits;

    uint8_t reg_byte;

}reg_SYS_CTL0_t;

Now all the bits inside this byte are named, and directly accessible.

Likewise, when entities are configured using more than one bit, like the LightLoadShutdownTime from before in register 0x02, a struct simplifies the handling enormously:

/*SYS_CTL2*/
union{
    struct{
       uint8_t RSVD                              : 2;
       uint8_t LIGHT_LOAD_SHUTDOWN_TIME          : 2;
       uint8_t LONG_PRESS_TIME                   : 1;
       uint8_t RSVD2                             : 3;  
    }bits;

    uint8_t reg_byte;
}reg_SYS_CTL2_t;

You can now read the relevant two bits via LIGHT_LOAD_SHUTDOWN_TIME. Unfortunately, the author is still returning uint8_t, so while it is now much easier to read the required bits, you still need to interpret the resulting byte yourself.

Setting (writing) these bits is easier since the author has defined constants:

/*SHUTDOWN_TIME_VALUE*/
#define SHUTDOWN_8s                                 0
#define SHUTDOWN_32s                                1
#define SHUTDOWN_16s                                2
#define SHUTDOWN_64s                                3

Room for Improvement

It would take only a small step to improve this library even further, so you would no longer need to look up values in I2C register maps.

This is how the library currently works:

union {
    struct {
        uint8_t RSVD                      : 2;
        uint8_t LIGHT_LOAD_SHUTDOWN_TIME  : 2;
        uint8_t LONG_PRESS_TIME           : 1;
        uint8_t RSVD2                     : 3;
    } bits;
    uint8_t reg_byte;
} reg_SYS_CTL2_t;

/* SHUTDOWN_TIME_VALUE */
#define SHUTDOWN_8s   0
#define SHUTDOWN_32s  1
#define SHUTDOWN_16s  2
#define SHUTDOWN_64s  3

And this is how a more modern and object-oriented approach would look like:

// define possible values as a enum:
enum class ShutdownTime : uint8_t {
    S8  = 0,  // 8 seconds
    S32 = 1,  // 32 seconds
    S16 = 2,  // 16 seconds
    S64 = 3   // 64 seconds
};

// define the structure of the byte that the particular I2C register uses:
struct SYS_CTL2_Bits {
    uint8_t RSVD                      : 2;
    uint8_t LIGHT_LOAD_SHUTDOWN_TIME  : 2;
    uint8_t LONG_PRESS_TIME           : 1;
    uint8_t RSVD2                     : 3;
};

// create a union (map the raw byte to the struct): 
union reg_SYS_CTL2_t {
    SYS_CTL2_Bits bits;
    uint8_t reg_byte;
};

// create type-safe setter and getter functions:
inline void set_shutdown_time(reg_SYS_CTL2_t& reg, ShutdownTime time) {
    reg.bits.LIGHT_LOAD_SHUTDOWN_TIME = static_cast<uint8_t>(time);
}

inline ShutdownTime get_shutdown_time(const reg_SYS_CTL2_t& reg) {
    return static_cast<ShutdownTime>(reg.bits.LIGHT_LOAD_SHUTDOWN_TIME);
}

From a users perspective, the code would now be simplified and type-safe, with no room for misunderstandings and unclear values:

// define variable to hold the I2C register 0x02:
reg_SYS_CTL2_t reg{};

// Set shutdown time to 16 seconds
set_shutdown_time(reg, ShutdownTime::S16);

// Read shutdown time
ShutdownTime t = get_shutdown_time(reg);
if (t == ShutdownTime::S16) {
    // Do something
}

Materials

IP5306 Datasheet
IP5306 I2C Register Map FM5324GA (IP5306 Clone) Translated English (translated)
FM5324GA (IP5306 Clone) Chinese Original (Chinese original)

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^{_{(content created Jan 12, 2025 - last updated Jun 13, 2025)}}