# Zephyr USB Command Handler

This repository contains the implementation of a USB command handler for the Zephyr RTOS. The system allows devices to communicate via USB using custom command messages.

### Components

1. **command_handler.c/h**: Handles incoming commands, processes them, and performs actions based on the command type.
2. **command_message.c/h**: Manages the creation, validation, and logging of command messages, including CRC calculation.
3. **usb.c/h**: Manages USB initialization, data reception via UART, and sending responses. Includes a USB thread.
4. **usb_conf.c/h**: Configures the USB device.

### Command Structure

```c
struct command_message_t {
    uint8_t prefix;     // 0x69
    uint8_t length;
    uint8_t id;
    uint8_t command;
    uint8_t crc;
    uint8_t data[160];
} __attribute__((packed));
```

### CRC Calculation Function

```c
uint8_t calculate_crc(struct command_message_t *msg) {
    uint32_t sum = 0;
    uint8_t crc = 0;

    uint8_t *byte_ptr = (uint8_t *)msg;

    for (int i = 0; i < (sizeof(struct command_message_t) - sizeof(msg->data) + msg->length) - 1; i++) {
        sum += byte_ptr[i];
    }

    crc = 0x100 - (sum & 0xff);

    return crc;
}
```

### Python test script (AI generated)

**Command Usage:**

```bash
python3 scripts/led_blink.py
```

This script sends LED toggle commands to the device connected via USB.