# SINAD inicator SPECs (R909-SINAD inicator)

##Arduino IDE (ESP32-C3 sketch)

## the hardware 

ESP32-C3 SUPER MINI DEV KIT
├── GPIO1  ← ADC input（audio signal）
├── GPIO2  ← rotary encoder A phase
├── GPIO3  ← rotary encoder B phase 
├── GPIO4  ← rotary encoder switch
├── GPIO5  → 
├── GPIO6  → 1kHz pulse output
├── GPIO7  → for checking loop timing
├── GPIO8  ↔ I2C SDA（OLED）
└── GPIO9  ↔ I2C SCL（OLED）
```

## the software

### 1. signal generator
```
[DDS signal ]
└── GPIO6: 1kHz pulse output（2kHz ON/OFF）
```

### 2. signal aquision processing
```
[ADC aquision] (200ms cycle)
analogRead(GPIO1) → 512 samples @ 10kHz
        ↓
voltage converted: (ADC-1473)/4096 * 3.3V
        ↓
[siganl processing]
inputBuffer[512] → the original data
        ↓
applyNotchFilter() → feeding for notch（1kHz, Q=10）
        ↓
notchBuffer[512] → the filtered signal
        ↓
[calculation]
calculateRMS(inputBuffer) → input value by RMS
calculateRMS(notchBuffer) → notched value by RMS
        ↓
calculateSINAD() → to get SINAD value
```

### 3. man machine interface
```
[operation]
rotary encoder → switching display Mode（6 modes)
rotary encoder SW → DDS ON/OFF switch

[displaying]
OLED SSD1306 (i2c)
├── Mode 0: SINAD display
├── Mode 1: wave display
├── Mode 2: wave display enlarged
├── Mode 3: wave display notched
├── Mode 4: wave display notched,  enlarged
├── Mode 5: FFT display
├── Mode 6: FFT display notched
├── Mode 7: parameter monitor
└── Mode 8: tuning sampling timing
```

### 4. controle・managing
```
[main]
setup() → initializing
├── assign ports
├── assign interrupt
├── set the DDS
├── set the notch filter
└── set the OLED

loop() → main（200ms cyccling）
├── sence the switches
├── sence the encoder
├── get ADC・process the signals
└── refresh display
```

## data flow
```
recieved signal → ADC(GPIO1) → conversion → inputBuffer
                                        ↓
inputBuffer → filtered → notchBuffer
                                        ↓
RMS calculation → SINAD issued → display

the test signal (turning on/off by RE-SW pushing）
DDS test signal output (GPIO6) → 1kHzパルスpulse
```
test signal　(turned on by F-SW1 pushing）
issue  the inbuffer[] 512 samples on serial port
```
test signal　(set precise tuning mode by F-SW2 pushing）
get into Mode 8 and inclease or decrease ADC sampling adjustment setting
```

## the majar parameters
- **DDS**: 2kHz refreshing rate  ON/OFF
- **ADC**: 10kHz sampling、512 smples/cycle
- **notch filter**: 1kHz、Q=10
- **display refresh**: 200ms cycle
- **ADC offset**: 1473 (about 1.18V)

## testing function↓(turning on with pressing SW1)
already calculated 1kHz mode
- **testwaveEnabled**: generated inside testing value
　512 samples calculated of  1kHz→ start by input Buffer preset