# AXP2101 PMU eFuse configuration after replacement – help needed

**URL:** <https://forum.clockworkpi.com/t/axp2101-pmu-efuse-configuration-after-replacement-help-needed/21627>\
**Category:** PicoCalc\
**Created:** [February 22, 2026, 9:51am UTC](https://forum.clockworkpi.com/t/axp2101-pmu-efuse-configuration-after-replacement-help-needed/21627 "2026-02-22T09:51:22Z")\
**Posts on this page:** 1\
**Showing post:** 5

<div class="post-metadata">

**Author:** ![Dawid\_Rychter](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.clockworkpi.com/dawid_rychter/32/16552_2.png) [@Dawid\_Rychter](https://forum.clockworkpi.com/u/Dawid_Rychter)\
**Post date:** [May 18, 2026, 2:42pm UTC](https://forum.clockworkpi.com/t/axp2101-pmu-efuse-configuration-after-replacement-help-needed/21627/5 "2026-05-18T14:42:08Z")

</div>

I was in the same situation, accidentally inserted my battery in reverse and killed AXP2101. I replaced it with the one I bought on aliexpress, but my LCD was not comming up after this replacement. Then I found this thread and thanks to the dump of orginal values of the stock AXP registers provided by @cathiele I was able to fix it. I used @JackCarterSmith rewrite of the picocalc BIOS described here:

> [@Custom PicoCalc BIOS/keyboard firmware](https://forum.clockworkpi.com/t/custom-picocalc-bios-keyboard-firmware/17292):
>
> Hi everyone, I redesigned the original STM32 firmware of the picocalc (aka “BIOS” or keyboard driver) to better suit my needs. A brief overview of the differences: persistent saving of settings like backlight, internal use of the RTC (provide external access through I2C), drastic reduction in static power consumption, removed stm32duino dependency, sleep mode, pico reset shortcut, reduced (probably wiped out) duplicate key press, … Here is the source [https://git.jcsmith.fr/jackcartersmith/p…](https://git.jcsmith.fr/jackcartersmith/picocalc_BIOS)

GIT:

> **[picocalc\_BIOS](https://git.jcsmith.fr/jackcartersmith/picocalc_BIOS)**
>
> Picocalc STM32F103R8T6 custom firmware

What I basically did is:

modified `Src/axp2101.c` file and added:

```auto
#define AXPI2C_RETRIES 3
#define AXPI2C_TIMEOUT_MS 100

typedef struct {
    uint8_t reg;
    uint8_t val;
} reg_pair_t;

static const reg_pair_t axp_init[] = {
    {0x12,0x00},
    {0x22,0x04},
    {0x24,0x00},
    {0x25,0x19},
    {0x27,0x16},
    {0x58,0x00},
    {0x50,0x12},
    {0x62,0x13},
    {0x69,0x01},
    {0x80,0x01},
    {0x82,0x12},
    {0x83,0x00},
    {0x84,0x00},
    {0x85,0x00},
    {0x90,0x3F},
    {0x91,0x00},
    {0x92,0x1C},
    {0x93,0x1C},
    {0x94,0x1C},
    {0x95,0x1C},
    {0x96,0x1E},
    {0x97,0x1E},
    {0x98,0x00},
    {0x99,0x00},
    {0x9A,0x00},
};

static HAL_StatusTypeDef axp2101_write_reg(uint8_t reg, uint8_t val)
{
    HAL_StatusTypeDef ret;
    for (int attempt = 0; attempt < AXPI2C_RETRIES; ++attempt) {
        ret = HAL_I2C_Mem_Write(&hi2c2, AXP2101_DEV_I2C_ID, reg, I2C_MEMADD_SIZE_8BIT, &val, 1, AXPI2C_TIMEOUT_MS);
        if (ret == HAL_OK) return HAL_OK;
        HAL_Delay(5);
    }
    return ret;
}

int axp2101_init_regs(void)
{
    size_t n = sizeof(axp_init)/sizeof(axp_init[0]);
    for (size_t i = 0; i < n; ++i) {
        HAL_StatusTypeDef s = axp2101_write_reg(axp_init[i].reg, axp_init[i].val);
        if (s != HAL_OK) {
            // TODO: error handle
            return -1;
        }
    }
    return 0;
}

```

modified `Inc/axp2101.h` and added function declaration:

`int axp2101_init_regs(void);`

and then modified `main.c` file and added the following after AXP initialization in `main()` (after line 195)

```auto
            if (axp2101_init_regs() != 0) {
                    // TODO: error handling
            }

```

and BUM, it works! Maybe this will help you as well.

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