# ESP32-C3 SPI Slave with ESP-NOW Project

This ESP-IDF project implements an SPI slave device that broadcasts received data via ESP-NOW with the following GPIO configuration:

- **MOSI**: GPIO10
- **MISO**: GPIO9  
- **SCLK**: GPIO20
- **CS**: GPIO7

## Features

- SPI Mode 0 (CPOL=0, CPHA=0)
- 256-byte buffer for data exchange
- DMA support for efficient transfers
- Real-time data logging via UART
- **ESP-NOW broadcasting** of received SPI data
- Timestamped data packets
- Broadcast to all nearby ESP32 devices

## Building and Flashing

1. Set up ESP-IDF environment:
   ```bash
   . $HOME/esp/esp-idf/export.sh
   ```

2. Build the project:
   ```bash
   cd esp32
   idf.py build
   ```

3. Flash to ESP32-C3:
   ```bash
   idf.py -p /dev/ttyUSB0 flash monitor
   ```

## Usage

The ESP32-C3 will act as an SPI slave device, waiting for transactions from an SPI master. When data is received, it will:

1. Print the received data to the serial console
2. **Broadcast the received data via ESP-NOW** to all nearby ESP32-C3 devices
3. Send back a test pattern (0x00, 0x01, 0x02, ...)
4. Wait for the next transaction

## ESP-NOW Data Format

The broadcasted data includes:
- **Data**: The actual SPI received data (up to 256 bytes)
- **Length**: Number of bytes received
- **Timestamp**: Millisecond timestamp when data was received

## Receiving ESP-NOW Data

To receive the broadcasted data on another ESP32-C3 device, you can use the ESP-NOW receive callback function. The data structure is:

```c
typedef struct {
    uint8_t data[256];    // Received SPI data
    uint8_t length;       // Number of bytes
    uint32_t timestamp;   // Timestamp in milliseconds
} espnow_data_t;
```

## Serial Monitor

Connect to the serial monitor to see debug output:
```bash
idf.py -p /dev/ttyUSB0 monitor
```

The device will log received SPI data and transaction status.