🚀 Multi-Slave SPI Communication System

Sistem Komunikasi SPI Master-Slave dengan Protocol Custom

Real-time monitoring • Fast & Non-blocking • PC Control Interface

📡

SPI Protocol

Custom packet format

⚡

High Speed

2 MHz, 100 Hz

💾

EEPROM

Auto backup

🖥️

PC Interface

Serial control

📐 Arsitektur Sistem

Hardware Configuration

Pin	Master	Slave
MOSI	51	11
MISO	50	12
SCK	52	13
SS1/2/3	A13/A14/A15	10

SPI Configuration

Parameter	Master	Slave
Mode	Master	Slave
Clock	2 MHz	Follow
Data Mode	MODE0	MODE0
Baud	115200	9600

📦 Format Paket

Request (Master → Slave): 5 bytes

[0xFF] [0xFE] [ID] [CMD] [CS]
 SYNC1  SYNC2  0x01 0x01  ID^CMD

Response (Slave → Master)

Single Byte: 5 bytes

[0xFF] [0xFE] [ID] [DATA] [CS]

16-bit Data: 6 bytes

[0xFF] [0xFE] [ID] [HIGH] [LOW] [CS]

🎮 Command Set

SPI Commands

Command	Value	Description
CMD_READ_VALUE	0x01	Read PB2
CMD_READ_SENSOR	0x02	Read ADC
CMD_READ_COUNTER	0x03	Read Counter

PC Commands (Serial)

Command	Output
X1	>>> PB2
X2	>>> ADC
X3	>>> PB2 ADC
X7	>>> PB2 ADC CNT
STOP	[Display stopped]

🔄 Alur Data (Step 1-6)

Step 1: PC Request

PC: 13 // Slave 1, PB2+ADC

↓

Step 2: Master Parse

slaveNum = 1; dataSelect = 3;

↓

Step 3: Master → Slave (CMD 0x01)

[0xFF 0xFE 0x01 0x01 0x00]

↓

Step 4: Slave Process

ISR validates & prepares response

↓

Step 5: Slave → Master

[0xFF 0xFE 0x01 0x01 0x00] // PB2=1

↓

Step 6: Master Validate

Read 15 bytes, find sync, validate CS

🔄 Alur Data (Step 7-12)

Step 7: Master → Slave (CMD 0x02)

[0xFF 0xFE 0x01 0x02 0x03]

↓

Step 8: Slave → Master (16-bit)

[0xFF 0xFE 0x01 0x03 0x40 0x42] // 832

↓

Step 9: Master Parse 16-bit

value = (0x03 << 8) | 0x40 = 832

↓

Step 10: Save EEPROM

EEPROM[0x00-0x03] = {1, 0x03, 0x40, cnt}

↓

Step 11: Display PC

Serial: ">>> 1 832"

↓

Step 12: Loop (100 Hz)

Repeat every 10ms until STOP

🔍 Parsing & Validation

Master: Find Sync Pattern

for (int i = 0; i < 10; i++) {
    if (buf[i]==0xFF && buf[i+1]==0xFE && buf[i+2]==ID) {
        if (validateChecksum()) return parseData();
    }
}

Slave: State Machine

WAIT_SYNC1 → WAIT_SYNC2 → WAIT_ID → 
WAIT_CMD → WAIT_CS → SEND_RESPONSE

🔐 Checksum

XOR Algorithm

// Request
CS = ID ^ CMD = 0x01 ^ 0x02 = 0x03

// Response (single)
CS = ID ^ DATA = 0x01 ^ 0x01 = 0x00

// Response (16-bit)
CS = ID ^ HIGH ^ LOW = 0x01 ^ 0x03 ^ 0x40 = 0x42

⚡ Timing & Performance

2 MHzSPI Clock

100 HzUpdate Rate

~2 msLatency

Communication Timeline

Time (ms)	Event
0.000	PC sends command
0.002	Master activates SS
0.007	Request sent
0.015	Slave responds
0.020	SS deactiviv
0.022	Parse & validate
0.025	Display to PC

💾 EEPROM Storage

Memory Map

Address	Slave	Data
0x00-0x03	Slave 1	PB2,ADC_H,ADC_L,CNT
0x04-0x07	Slave 2	PB2,ADC_H,ADC_L,CNT
0x08-0x0B	Slave 3	PB2,ADC_H,ADC_L,CNT

Save/Load

// Save
EEPROM.update(base+0, pb2);
EEPROM.update(base+1, adc>>8);
EEPROM.update(base+2, adc&0xFF);
EEPROM.update(base+3, cnt);

// Load
pb2 = EEPROM.read(base+0);
adc = (EEPROM.read(base+1)<<8) | EEPROM.read(base+2);

🖥️ LCD Display

16x2 LCD Format

┌────────────────┐
│S1 P:1 A:832    │
│   C:5 OK       │
└────────────────┘

Update Code

lcd.clear();
lcd.setCursor(0,0);
lcd.print("S1 P:" + pb2 + " A:" + adc);
lcd.setCursor(0,1);
lcd.print("   C:" + cnt + (valid ? " OK" : " ER"));

Rotates every 500ms: S1 → S2 → S3 → S1

🛡️ Error Handling

Error Detection

Error	Detection	Action
Checksum fail	XOR mismatch	Return 0xFF/0xFFFF
No sync	Pattern not found	Return error
Wrong ID	ID mismatch	Ignore, reset state
No response	Timeout	Mark invalid

Master Error Handling

if (pb2 == 0xFF || adc == 0xFFFF) {
    data.valid = false;
    return false;
}
data.valid = true;
saveToEEPROM();

🌟 Keunggulan Sistem

🚀

Performance

2 MHz SPI
100 Hz rate
Non-blocking
~2ms latency

🔒

Reliable

Checksum
Sync pattern
Error recovery
State machine

💾

Persistent

Auto EEPROM
Fast response
No data loss
100k cycles

📡

Scalable

3 slaves
Easy expand
Custom CMD
Flexible

📌 Summary

Multi-Slave SPI Communication System

Sistem komunikasi SPI yang menghubungkan 1 Master dengan 3 Slave menggunakan custom protocol dengan sync pattern dan checksum validation. Master dapat berkomunikasi dengan PC via Serial untuk real-time monitoring dengan kecepatan hingga 100 updates/detik.

Data Flow

PC → Master → Slave → EEPROM → Display

PC: "17" (Slave 1, All data)
Master polls via SPI (3 commands)
Slave responds with validated data
Master saves to EEPROM
Display: ">>> 1 832 5"
Repeat @ 100 Hz until "STOP"

2 MHzSPI Speed

100 HzDisplay Rate

~2 msLatency

3 SlavesScalable

Thank You! 🚀

Multi-Slave SPI Communication System

Questions & Discussion