# Internal and Unstable APIs

[中文]

This section is listing some APIs that are internal or likely to be changed or removed in the next releases of ESP-IDF.

## API Reference

### Header File

- components/esp_rom/include/esp_rom_sys.h

- This header file can be included with:

  >     #include "esp_rom_sys.h"

### Functions

void esp_rom_software_reset_system(void)

  Software Reset digital core include RTC.

  It is not recommended to use this function in esp-idf, use esp_restart() instead.

void esp_rom_software_reset_cpu(int cpu_no)

  Software Reset cpu core.

  It is not recommended to use this function in esp-idf, use esp_restart() instead.

  Parameters:

    cpu_no -- : The CPU to reset, 0 for PRO CPU, 1 for APP CPU.

int esp_rom_printf(const char *fmt, ...)

  Print formatted string to console device.

  Note

  float and long long data are not supported!

  Parameters:

    - fmt -- Format string

    - ... -- Additional arguments, depending on the format string

  Returns:

    int: Total number of characters written on success; A negative number on failure.

int esp_rom_vprintf(const char *fmt, va_list ap)

  Print formatted string to console device.

  Note

  float and long long data are not supported!

  Parameters:

    - fmt -- Format string

    - ap -- List of arguments.

  Returns:

    int: Total number of characters written on success; A negative number on failure.

int esp_rom_cvt(unsigned long long val, long radix, int pad, const char *digits, char *buf)

  Convert an unsigned integer value to a string representation in the specified radix.

  This function converts the given unsigned integer value to a string representation in the specified radix. The resulting string is stored in the provided character buffer `buf`.

  Note

  The buffer `buf` must have sufficient space to hold the entire converted string, including the null-terminator. The caller is responsible for ensuring the buffer's size is large enough to prevent buffer overflow.

  Note

  The provided `digits` array must have enough elements to cover the entire radix used for conversion. Otherwise, undefined behavior may occur.

  Parameters:

    - val -- [in] The unsigned integer value to be converted.

    - radix -- [in] The base of the numeral system to be used for the conversion. It determines the number of unique digits in the numeral system (e.g., 2 for binary, 10 for decimal, 16 for hexadecimal).

    - pad -- [in] The optional padding width (0 - unused) for the resulting string. It adds zero-padding. (val=123, pad=6 -> result=000123).

    - digits -- [in] Pointer to a character array representing the digits of the numeral system. The array must contain characters in the order of increasing values, corresponding to the digits of the radix. For example, "0123456789ABCDEF" or hexadecimal.

    - buf -- [out] Pointer to the character buffer where the resulting string will be stored. The buffer must have enough space to accommodate the entire converted string, including the null-terminator.

  Returns:

    The length of the resulting string (excluding the null-terminator).

void esp_rom_delay_us(uint32_t us)

  Pauses execution for us microseconds.

  Parameters:

    us -- Number of microseconds to pause

void esp_rom_install_channel_putc(int channel, void (*putc)(char c))

  esp_rom_printf can print message to different channels simultaneously. This function can help install the low level putc function for esp_rom_printf.

  Parameters:

    - channel -- Channel number (starting from 1)

    - putc -- Function pointer to the putc implementation. Set NULL can disconnect esp_rom_printf with putc.

void esp_rom_output_to_channels(char c)

  It outputs a character to different channels simultaneously. This function is used by esp_rom_printf/esp_rom_vprintf.

  Parameters:

    c -- Char to output.

void esp_rom_install_uart_printf(void)

  Install UART1 as the default console channel, equivalent to `esp_rom_install_channel_putc(1, esp_rom_output_putc)`

soc_reset_reason_t esp_rom_get_reset_reason(int cpu_no)

  Get reset reason of CPU.

  Parameters:

    cpu_no -- CPU number

  Returns:

    Reset reason code (see in soc/reset_reasons.h)

void esp_rom_route_intr_matrix(int cpu_core, uint32_t periph_intr_id, uint32_t cpu_intr_num)

  Route peripheral interrupt sources to CPU's interrupt port by matrix.

  Usually there're 4 steps to use an interrupt:

  1. Route peripheral interrupt source to CPU. e.g. esp_rom_route_intr_matrix(0, ETS_WIFI_MAC_INTR_SOURCE, ETS_WMAC_INUM)

  2. Set interrupt handler for CPU

  3. Enable CPU interrupt

  4. Enable peripheral interrupt

  Parameters:

    - cpu_core -- The CPU number, which the peripheral interrupt will inform to

    - periph_intr_id -- The peripheral interrupt source number

    - cpu_intr_num -- The CPU (external) interrupt number. On targets that use CLIC as their interrupt controller, this number represents the external interrupt number. For example, passing `cpu_intr_num = i` to this function would in fact bind peripheral source to CPU interrupt `CLIC_EXT_INTR_NUM_OFFSET + i`.

uint32_t esp_rom_get_cpu_ticks_per_us(void)

  Get the real CPU ticks per us.

  Returns:

    CPU ticks per us

void esp_rom_set_cpu_ticks_per_us(uint32_t ticks_per_us)

  Set the real CPU tick rate.

  Note

  Call this function when CPU frequency is changed, otherwise the `esp_rom_delay_us` can be inaccurate.

  Parameters:

    ticks_per_us -- CPU ticks per us

uint32_t esp_rom_get_bootloader_offset(void)

  Returns the offset from which the bootloader image is used to load.

  The offset can point to either the PRIMARY or RECOVERY bootloader.

  Returns:

    The offset of the active bootloader.

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