API Reference Overview

Complete reference for AkiraOS WASM application APIs.

Looking for the high-level SDK API? See the SDK API Reference for event system, display, input, sensors, RF, storage, network, and system functions with full examples.

Available APIs

AkiraOS provides a custom native API for WASM applications. This is not WASI—it’s optimized for embedded systems and real-time constraints.

API Categories

Category	Functions	Purpose
Display	5 functions	Screen rendering
Input	3 functions	Button/touch input
Sensors	2 functions	IMU, temperature, etc.
RF/Network	4 functions	WiFi, BT, LoRa
File System	5 functions	Persistent storage
Logging	3 functions	Debug output
Time	2 functions	Timing and delays

Import Module

All native functions are imported from the "akira" module:

__attribute__((import_module("akira")))
__attribute__((import_name("log")))
extern void akira_log(const char *message, uint32_t len);

Display API

display_clear

Clear the entire screen to a specific color.

__attribute__((import_module("akira")))
__attribute__((import_name("display_clear")))
extern int akira_display_clear(uint32_t color);

Parameters:

• color: 24-bit RGB color (0xRRGGBB)

Returns: 0 on success, negative on error

Capability Required: CAP_DISPLAY_WRITE

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display_pixel

Draw a single pixel.

__attribute__((import_module("akira")))
__attribute__((import_name("display_pixel")))
extern int akira_display_pixel(uint32_t x, uint32_t y, uint32_t color);

Parameters:

• x, y: Pixel coordinates
• color: 24-bit RGB color

Returns: 0 on success, negative on error

Capability Required: CAP_DISPLAY_WRITE

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display_rect

Draw a filled rectangle.

extern int akira_display_rect(uint32_t x, uint32_t y,
                              uint32_t width, uint32_t height,
                              uint32_t color);

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display_text

Render text string.

extern int akira_display_text(uint32_t x, uint32_t y,
                              const char *text, uint32_t len,
                              uint32_t color);

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display_flush

Flush framebuffer to screen (if buffered).

extern int akira_display_flush();

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Input API

input_read_buttons

Read digital button states.

__attribute__((import_module("akira")))
__attribute__((import_name("input_read_buttons")))
extern uint32_t akira_input_read_buttons();

Returns: Bitmask of button states (1 = pressed)

Capability Required: CAP_INPUT_READ

Button Mapping:

• Bit 0: Button A
• Bit 1: Button B
• Bit 2: Button C
• Bit 3: Button D

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input_read_touch

Read touchscreen coordinates.

extern int akira_input_read_touch(uint32_t *x, uint32_t *y);

Returns: 0 if touched, -1 if not

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Sensor API

sensor_read

Read sensor value by ID.

__attribute__((import_module("akira")))
__attribute__((import_name("sensor_read")))
extern int akira_sensor_read(uint32_t sensor_id, float *data);

Parameters:

• sensor_id: Sensor identifier (0-15)
• data: Pointer to receive sensor value

Returns: 0 on success, negative on error

Capability Required: CAP_SENSOR_READ

Sensor IDs:

• 0: Temperature (°C)
• 1: Humidity (%)
• 2: Pressure (hPa)
• 3: Accel X (m/s²)
• 4: Accel Y
• 5: Accel Z
• 6: Gyro X (°/s)
• 7: Gyro Y
• 8: Gyro Z

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RF/Network API

rf_send

Send data via RF interface.

__attribute__((import_module("akira")))
__attribute__((import_name("rf_send")))
extern int akira_rf_send(const uint8_t *data, uint32_t len);

Capability Required: CAP_RF_TRANSCEIVE

Max Length: 256 bytes per call

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rf_recv

Receive data from RF interface.

extern int akira_rf_recv(uint8_t *buffer, uint32_t max_len);

Returns: Bytes received, or 0 if no data

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File System API

fs_read

Read file contents.

extern int akira_fs_read(const char *path, uint8_t *buffer, uint32_t max_len);

Capability Required: CAP_FS_READ

Path Restriction: Apps can only access /data/<app_name>/

---

fs_write

Write file contents.

__attribute__((import_module("akira")))
__attribute__((import_name("fs_write")))
extern int akira_fs_write(const char *path, const uint8_t *data, uint32_t len);

Capability Required: CAP_FS_WRITE

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fs_stat

Get file information.

extern int akira_fs_stat(const char *path, uint32_t *size);

Returns: 0 if file exists, -1 otherwise

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Logging API

log

Write log message.

__attribute__((import_module("akira")))
__attribute__((import_name("log")))
extern void akira_log(const char *message, uint32_t len);

No capability required - Always available

Max Length: 256 characters

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Time API

time_ms

Get current time in milliseconds since boot.

extern uint64_t akira_time_ms();

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sleep_ms

Sleep for specified milliseconds.

extern void akira_sleep_ms(uint32_t ms);

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Error Codes

Code	Constant	Meaning
0	OK	Success
-1	EPERM	Permission denied (capability)
-2	ENOENT	File not found
-3	EIO	I/O error
-12	ENOMEM	Out of memory
-22	EINVAL	Invalid argument

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Complete Example

#include <stdint.h>
#include <string.h>

// Import native functions
__attribute__((import_module("akira")))
__attribute__((import_name("log")))
extern void akira_log(const char *msg, uint32_t len);

__attribute__((import_module("akira")))
__attribute__((import_name("display_clear")))
extern int akira_display_clear(uint32_t color);

__attribute__((import_module("akira")))
__attribute__((import_name("input_read_buttons")))
extern uint32_t akira_input_read_buttons();

__attribute__((import_module("akira")))
__attribute__((import_name("sensor_read")))
extern int akira_sensor_read(uint32_t id, float *data);

// Entry point
__attribute__((export_name("_start")))
void app_main() {
    akira_log("App starting", 12);
    
    // Clear screen to blue
    akira_display_clear(0x0000FF);
    
    // Read temperature
    float temp = 0.0f;
    if (akira_sensor_read(0, &temp) == 0) {
        char msg[64];
        snprintf(msg, sizeof(msg), "Temp: %.2f C", temp);
        akira_log(msg, strlen(msg));
    }
    
    // Wait for button press
    while (!(akira_input_read_buttons() & 0x01)) {
        // Busy wait (bad practice, use sleep in real app)
    }
    
    akira_log("Button pressed!", 14);
}

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Type Reference

WASM Function Signatures

When registering native functions in WAMR, these signatures are used:

• "($)v" - String parameter, void return
• "(i)i" - Int parameter, int return
• "(ii)i" - Two int params, int return
• "(*)i" - Pointer param, int return
• "(*i)i" - Pointer and int, int return
• "()i" - No params, int return

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Related Documentation

• Manifest Format - Capability declarations
• Building Apps - WASM compilation
• First App Tutorial - Hello World
• Security Model - Capability system

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