Add ESP32-C3 SPI slave with ESP-NOW, Raspberry Pi test tools, and updated project structure

- ESP32-C3 SPI slave project with ESP-NOW broadcast functionality
- Raspberry Pi SPI master test tools and CLI for JSON communication
- Merged src/ directory from full branch with lighting controller code
- Updated Pipfile with system install scripts and ESP32 monitoring
- Added comprehensive test suite for SPI communication

esp32/README.md

@@ -0,0 +1,73 @@
+# 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.