ATtinny85 Getting Started Tutorial, and its programming with Arduino

ATtinny85 microcontroller:

ATtinny85 Microcontroller– ATtinny85 can be a best choice when planning to reduce the project size and development cost. With the ATtinny85 Microcontroller you can do amazing things as it can be programmed. You can program this beautiful piece of hardware using your Arduino Uno boards.  How you can program an ATinny85 using an Arduino Uno with some jumper wires but before that let’s just understands some basic behind ATtinny85. ATtinny85 is an 8-bit AVR microcontroller based on RISC CPU. It has eight pins and fall under category of low powered microcontrollers. It has programmable watchdog timer and 10 bit converter which make it suitable for many sensor based projects. It’s programmable memory is 8 kilobyte while the EEPROM and RAM contain memory space of around 512 bytes. It has 6 I/O pins which have internal pull-up resistors and its operational voltage is between 1.8 volt to 5 volts.

Features:

• High Performance, Low Power AVR® 8-Bit Microcontroller
• Advanced RISC Architecture

– 120 Powerful Instructions – Most Single Clock Cycle Execution

– 32 x 8 General Purpose Working Registers

– Fully Static Operation

• Non-volatile Program and Data Memories

– 2/4/8K Byte of In-System Programmable Program Memory Flash (ATtiny25/45/85)

Endurance: 10,000 Write/Erase Cycles

– 128/256/512 Bytes In-System Programmable EEPROM (ATtiny25/45/85)

Endurance: 100,000 Write/Erase Cycles

– 128/256/512 Bytes Internal SRAM (ATtiny25/45/85)

– Programming Lock for Self-Programming Flash Program and EEPROM Data

Security

• Peripheral Features

– 8-bit Timer/Counter with Prescaler and Two PWM Channels

– 8-bit High Speed Timer/Counter with Separate Prescaler

2 High Frequency PWM Outputs with Separate Output Compare Registers

Programmable Dead Time Generator

– USI – Universal Serial Interface with Start Condition Detector

– 10-bit ADC

4 Single Ended Channels

2 Differential ADC Channel Pairs with Programmable Gain (1x, 20x)

Temperature Measurement

– Programmable Watchdog Timer with Separate On-chip Oscillator

– On-chip Analog Comparator

• Special Microcontroller Features

– debugWIRE On-chip Debug System

– In-System Programmable via SPI Port

– External and Internal Interrupt Sources

– Low Power Idle, ADC Noise Reduction, and Power-down Modes

– Enhanced Power-on Reset Circuit

– Programmable Brown-out Detection Circuit

– Internal Calibrated Oscillator

• I/O and Packages

– Six Programmable I/O Lines

– 8-pin PDIP, 8-pin SOIC and 20-pad QFN/MLF

• Operating Voltage

– 1.8 – 5.5V for ATtiny25/45/85V

– 2.7 – 5.5V for ATtiny25/45/85

• Speed Grade

– ATtiny25/45/85V: 0 – 4 MHz @ 1.8 – 5.5V, 0 – 10 MHz @ 2.7 – 5.5V

– ATtiny25/45/85: 0 – 10 MHz @ 2.7 – 5.5V, 0 – 20 MHz @ 4.5 – 5.5V

• Industrial Temperature Range
• Low Power Consumption

– Active Mode:

1 MHz, 1.8V: 300 μA

– Power-down Mode:

0.1μA at 1.8V

ATinny85 Pinout:

Programming ATtinny85 microcontroller:

For programming ATtinny85 microcontroller, first you need to download the core files.

Step 1:

Now in order to add ATtinny85 board to Arduino IDE we will first open the Arduino IDE. Then in the Arduino IDE click on the file and in file click on the preference.

Step 2:

When we click on the preference a dialog box will appear:

Now in the additional boards manager paste the following link:

ATtinny Board Manager URL Link:

https://raw.githubusercontent.com/damellis/attiny/ide-1.6.x-boards-manager/package_damellis_attiny_index.json

After pasting the link, click on the ok.

Step 3:

Now in step 3 go to tools and in tools select the board and then click on the board manager.

Step 4:

In board manager different types of board will appear now select the attiny and click on the install.

Step 5:

Once the ATtinny is installed, close your Arduino IDE and open again. Now the attiny board is installed in order to open it we will go to the tool then select the board and then select the attiny microcontroller in which we will select the ATtinny 25/45/85

Step 6:

Now open the examples and select the Arduino ISP the code will appear.

Code:

// ArduinoISP
// Copyright (c) 2008-2011 Randall Bohn
// If you require a license, see
// http://www.opensource.org/licenses/bsd-license.php
//
// This sketch turns the Arduino into a AVRISP using the following Arduino pins:
//
// Pin 10 is used to reset the target microcontroller.
//
// By default, the hardware SPI pins MISO, MOSI and SCK are used to communicate
// with the target. On all Arduinos, these pins can be found
// on the ICSP/SPI header:
//
// MISO °. . 5V (!) Avoid this pin on Due, Zero…
// SCK . . MOSI
// . . GND
//
// On some Arduinos (Uno,…), pins MOSI, MISO and SCK are the same pins as
// digital pin 11, 12 and 13, respectively. That is why many tutorials instruct
// you to hook up the target to these pins. If you find this wiring more
// practical, have a define USE_OLD_STYLE_WIRING. This will work even when not
// using an Uno. (On an Uno this is not needed).
//
// Alternatively you can use any other digital pin by configuring
// software (‘BitBanged’) SPI and having appropriate defines for PIN_MOSI,
// PIN_MISO and PIN_SCK.
//
// IMPORTANT: When using an Arduino that is not 5V tolerant (Due, Zero, …) as
// the programmer, make sure to not expose any of the programmer’s pins to 5V.
// A simple way to accomplish this is to power the complete system (programmer
// and target) at 3V3.
//
// Put an LED (with resistor) on the following pins:
// 9: Heartbeat – shows the programmer is running
// 8: Error – Lights up if something goes wrong (use red if that makes sense)
// 7: Programming – In communication with the slave
//

#include “Arduino.h”
#undef SERIAL

#define PROG_FLICKER true

// Configure SPI clock (in Hz).
// E.g. for an ATtiny @ 128 kHz: the datasheet states that both the high and low
// SPI clock pulse must be > 2 CPU cycles, so take 3 cycles i.e. divide target
// f_cpu by 6:
// #define SPI_CLOCK (128000/6)
//
// A clock slow enough for an ATtiny85 @ 1 MHz, is a reasonable default:

#define SPI_CLOCK (1000000/6)

// Select hardware or software SPI, depending on SPI clock.
// Currently only for AVR, for other architectures (Due, Zero,…), hardware SPI
// is probably too fast anyway.

#if defined(ARDUINO_ARCH_AVR)

#if SPI_CLOCK > (F_CPU / 128)
#define USE_HARDWARE_SPI
#endif

#endif

// Configure which pins to use:

// The standard pin configuration.
#ifndef ARDUINO_HOODLOADER2

#define RESET 10 // Use pin 10 to reset the target rather than SS
#define LED_HB 9
#define LED_ERR 8
#define LED_PMODE 7

// Uncomment following line to use the old Uno style wiring
// (using pin 11, 12 and 13 instead of the SPI header) on Leonardo, Due…

// #define USE_OLD_STYLE_WIRING

#ifdef USE_OLD_STYLE_WIRING

#define PIN_MOSI 11
#define PIN_MISO 12
#define PIN_SCK 13

#endif

// HOODLOADER2 means running sketches on the ATmega16U2 serial converter chips
// on Uno or Mega boards. We must use pins that are broken out:
#else

#define RESET 4
#define LED_HB 7
#define LED_ERR 6
#define LED_PMODE 5

#endif

// By default, use hardware SPI pins:
#ifndef PIN_MOSI
#define PIN_MOSI MOSI
#endif

#ifndef PIN_MISO
#define PIN_MISO MISO
#endif

#ifndef PIN_SCK
#define PIN_SCK SCK
#endif

// Force bitbanged SPI if not using the hardware SPI pins:
#if (PIN_MISO != MISO) || (PIN_MOSI != MOSI) || (PIN_SCK != SCK)
#undef USE_HARDWARE_SPI
#endif

// Configure the serial port to use.
//
// Prefer the USB virtual serial port (aka. native USB port), if the Arduino has one:
// – it does not autoreset (except for the magic baud rate of 1200).
// – it is more reliable because of USB handshaking.
//
// Leonardo and similar have an USB virtual serial port: ‘Serial’.
// Due and Zero have an USB virtual serial port: ‘SerialUSB’.
//
// On the Due and Zero, ‘Serial’ can be used too, provided you disable autoreset.
// To use ‘Serial’: #define SERIAL Serial

#ifdef SERIAL_PORT_USBVIRTUAL
#define SERIAL SERIAL_PORT_USBVIRTUAL
#else
#define SERIAL Serial
#endif

// Configure the baud rate:

#define BAUDRATE 19200
// #define BAUDRATE 115200
// #define BAUDRATE 1000000

#define HWVER 2
#define SWMAJ 1
#define SWMIN 18

// STK Definitions
#define STK_OK 0x10
#define STK_FAILED 0x11
#define STK_UNKNOWN 0x12
#define STK_INSYNC 0x14
#define STK_NOSYNC 0x15
#define CRC_EOP 0x20 //ok it is a space…

void pulse(int pin, int times);

#ifdef USE_HARDWARE_SPI
#include “SPI.h”
#else

#define SPI_MODE0 0x00

class SPISettings {
public:
// clock is in Hz
SPISettings(uint32_t clock, uint8_t bitOrder, uint8_t dataMode) : clock(clock) {
(void) bitOrder;
(void) dataMode;
};

private:
uint32_t clock;

friend class BitBangedSPI;
};

class BitBangedSPI {
public:
void begin() {
digitalWrite(PIN_SCK, LOW);
digitalWrite(PIN_MOSI, LOW);
pinMode(PIN_SCK, OUTPUT);
pinMode(PIN_MOSI, OUTPUT);
pinMode(PIN_MISO, INPUT);
}

void beginTransaction(SPISettings settings) {
pulseWidth = (500000 + settings.clock – 1) / settings.clock;
if (pulseWidth == 0)
pulseWidth = 1;
}

void end() {}

uint8_t transfer (uint8_t b) {
for (unsigned int i = 0; i < 8; ++i) {
digitalWrite(PIN_MOSI, (b & 0x80) ? HIGH : LOW);
digitalWrite(PIN_SCK, HIGH);
delayMicroseconds(pulseWidth);
b = (b << 1) | digitalRead(PIN_MISO);
digitalWrite(PIN_SCK, LOW); // slow pulse
delayMicroseconds(pulseWidth);
}
return b;
}

private:
unsigned long pulseWidth; // in microseconds
};

static BitBangedSPI SPI;

#endif

void setup() {
SERIAL.begin(BAUDRATE);

pinMode(LED_PMODE, OUTPUT);
pulse(LED_PMODE, 2);
pinMode(LED_ERR, OUTPUT);
pulse(LED_ERR, 2);
pinMode(LED_HB, OUTPUT);
pulse(LED_HB, 2);

}

int error = 0;
int pmode = 0;
// address for reading and writing, set by ‘U’ command
unsigned int here;
uint8_t buff[256]; // global block storage

#define beget16(addr) (*addr * 256 + *(addr+1) )
typedef struct param {
uint8_t devicecode;
uint8_t revision;
uint8_t progtype;
uint8_t parmode;
uint8_t polling;
uint8_t selftimed;
uint8_t lockbytes;
uint8_t fusebytes;
uint8_t flashpoll;
uint16_t eeprompoll;
uint16_t pagesize;
uint16_t eepromsize;
uint32_t flashsize;
}
parameter;

parameter param;

// this provides a heartbeat on pin 9, so you can tell the software is running.
uint8_t hbval = 128;
int8_t hbdelta = 8;
void heartbeat() {
static unsigned long last_time = 0;
unsigned long now = millis();
if ((now – last_time) < 40)
return;
last_time = now;
if (hbval > 192) hbdelta = -hbdelta;
if (hbval < 32) hbdelta = -hbdelta;
hbval += hbdelta;
analogWrite(LED_HB, hbval);
}

static bool rst_active_high;

void reset_target(bool reset) {
digitalWrite(RESET, ((reset && rst_active_high) || (!reset && !rst_active_high)) ? HIGH : LOW);
}

void loop(void) {
// is pmode active?
if (pmode) {
digitalWrite(LED_PMODE, HIGH);
} else {
digitalWrite(LED_PMODE, LOW);
}
// is there an error?
if (error) {
digitalWrite(LED_ERR, HIGH);
} else {
digitalWrite(LED_ERR, LOW);
}

// light the heartbeat LED
heartbeat();
if (SERIAL.available()) {
avrisp();
}
}

uint8_t getch() {
while (!SERIAL.available());
return SERIAL.read();
}
void fill(int n) {
for (int x = 0; x < n; x++) {
buff[x] = getch();
}
}

#define PTIME 30
void pulse(int pin, int times) {
do {
digitalWrite(pin, HIGH);
delay(PTIME);
digitalWrite(pin, LOW);
delay(PTIME);
} while (times–);
}

void prog_lamp(int state) {
if (PROG_FLICKER) {
digitalWrite(LED_PMODE, state);
}
}

uint8_t spi_transaction(uint8_t a, uint8_t b, uint8_t c, uint8_t d) {
SPI.transfer(a);
SPI.transfer(b);
SPI.transfer(c);
return SPI.transfer(d);
}

void empty_reply() {
if (CRC_EOP == getch()) {
SERIAL.print((char)STK_INSYNC);
SERIAL.print((char)STK_OK);
} else {
error++;
SERIAL.print((char)STK_NOSYNC);
}
}

void breply(uint8_t b) {
if (CRC_EOP == getch()) {
SERIAL.print((char)STK_INSYNC);
SERIAL.print((char)b);
SERIAL.print((char)STK_OK);
} else {
error++;
SERIAL.print((char)STK_NOSYNC);
}
}

void get_version(uint8_t c) {
switch (c) {
case 0x80:
breply(HWVER);
break;
case 0x81:
breply(SWMAJ);
break;
case 0x82:
breply(SWMIN);
break;
case 0x93:
breply(‘S’); // serial programmer
break;
default:
breply(0);
}
}

void set_parameters() {
// call this after reading parameter packet into buff[]
param.devicecode = buff[0];
param.revision = buff[1];
param.progtype = buff[2];
param.parmode = buff[3];
param.polling = buff[4];
param.selftimed = buff[5];
param.lockbytes = buff[6];
param.fusebytes = buff[7];
param.flashpoll = buff[8];
// ignore buff[9] (= buff[8])
// following are 16 bits (big endian)
param.eeprompoll = beget16(&buff[10]);
param.pagesize = beget16(&buff[12]);
param.eepromsize = beget16(&buff[14]);

// 32 bits flashsize (big endian)
param.flashsize = buff[16] * 0x01000000
+ buff[17] * 0x00010000
+ buff[18] * 0x00000100
+ buff[19];

// AVR devices have active low reset, AT89Sx are active high
rst_active_high = (param.devicecode >= 0xe0);
}

void start_pmode() {

// Reset target before driving PIN_SCK or PIN_MOSI

// SPI.begin() will configure SS as output, so SPI master mode is selected.
// We have defined RESET as pin 10, which for many Arduinos is not the SS pin.
// So we have to configure RESET as output here,
// (reset_target() first sets the correct level)
reset_target(true);
pinMode(RESET, OUTPUT);
SPI.begin();
SPI.beginTransaction(SPISettings(SPI_CLOCK, MSBFIRST, SPI_MODE0));

// See AVR datasheets, chapter “SERIAL_PRG Programming Algorithm”:

// Pulse RESET after PIN_SCK is low:
digitalWrite(PIN_SCK, LOW);
delay(20); // discharge PIN_SCK, value arbitrarily chosen
reset_target(false);
// Pulse must be minimum 2 target CPU clock cycles so 100 usec is ok for CPU
// speeds above 20 KHz
delayMicroseconds(100);
reset_target(true);

// Send the enable programming command:
delay(50); // datasheet: must be > 20 msec
spi_transaction(0xAC, 0x53, 0x00, 0x00);
pmode = 1;
}

void end_pmode() {
SPI.end();
// We’re about to take the target out of reset so configure SPI pins as input
pinMode(PIN_MOSI, INPUT);
pinMode(PIN_SCK, INPUT);
reset_target(false);
pinMode(RESET, INPUT);
pmode = 0;
}

void universal() {
uint8_t ch;

fill(4);
ch = spi_transaction(buff[0], buff[1], buff[2], buff[3]);
breply(ch);
}

void flash(uint8_t hilo, unsigned int addr, uint8_t data) {
spi_transaction(0x40 + 8 * hilo,
addr >> 8 & 0xFF,
addr & 0xFF,
data);
}
void commit(unsigned int addr) {
if (PROG_FLICKER) {
prog_lamp(LOW);
}
spi_transaction(0x4C, (addr >> 8) & 0xFF, addr & 0xFF, 0);
if (PROG_FLICKER) {
delay(PTIME);
prog_lamp(HIGH);
}
}

unsigned int current_page() {
if (param.pagesize == 32) {
return here & 0xFFFFFFF0;
}
if (param.pagesize == 64) {
return here & 0xFFFFFFE0;
}
if (param.pagesize == 128) {
return here & 0xFFFFFFC0;
}
if (param.pagesize == 256) {
return here & 0xFFFFFF80;
}
return here;
}

void write_flash(int length) {
fill(length);
if (CRC_EOP == getch()) {
SERIAL.print((char) STK_INSYNC);
SERIAL.print((char) write_flash_pages(length));
} else {
error++;
SERIAL.print((char) STK_NOSYNC);
}
}

uint8_t write_flash_pages(int length) {
int x = 0;
unsigned int page = current_page();
while (x < length) {
if (page != current_page()) {
commit(page);
page = current_page();
}
flash(LOW, here, buff[x++]);
flash(HIGH, here, buff[x++]);
here++;
}

commit(page);

return STK_OK;
}

#define EECHUNK (32)
uint8_t write_eeprom(unsigned int length) {
// here is a word address, get the byte address
unsigned int start = here * 2;
unsigned int remaining = length;
if (length > param.eepromsize) {
error++;
return STK_FAILED;
}
while (remaining > EECHUNK) {
write_eeprom_chunk(start, EECHUNK);
start += EECHUNK;
remaining -= EECHUNK;
}
write_eeprom_chunk(start, remaining);
return STK_OK;
}
// write (length) bytes, (start) is a byte address
uint8_t write_eeprom_chunk(unsigned int start, unsigned int length) {
// this writes byte-by-byte, page writing may be faster (4 bytes at a time)
fill(length);
prog_lamp(LOW);
for (unsigned int x = 0; x < length; x++) {
unsigned int addr = start + x;
spi_transaction(0xC0, (addr >> 8) & 0xFF, addr & 0xFF, buff[x]);
delay(45);
}
prog_lamp(HIGH);
return STK_OK;
}

void program_page() {
char result = (char) STK_FAILED;
unsigned int length = 256 * getch();
length += getch();
char memtype = getch();
// flash memory @here, (length) bytes
if (memtype == ‘F’) {
write_flash(length);
return;
}
if (memtype == ‘E’) {
result = (char)write_eeprom(length);
if (CRC_EOP == getch()) {
SERIAL.print((char) STK_INSYNC);
SERIAL.print(result);
} else {
error++;
SERIAL.print((char) STK_NOSYNC);
}
return;
}
SERIAL.print((char)STK_FAILED);
return;
}

uint8_t flash_read(uint8_t hilo, unsigned int addr) {
return spi_transaction(0x20 + hilo * 8,
(addr >> 8) & 0xFF,
addr & 0xFF,
0);
}

char flash_read_page(int length) {
for (int x = 0; x < length; x += 2) {
uint8_t low = flash_read(LOW, here);
SERIAL.print((char) low);
uint8_t high = flash_read(HIGH, here);
SERIAL.print((char) high);
here++;
}
return STK_OK;
}

char eeprom_read_page(int length) {
// here again we have a word address
int start = here * 2;
for (int x = 0; x < length; x++) {
int addr = start + x;
uint8_t ee = spi_transaction(0xA0, (addr >> 8) & 0xFF, addr & 0xFF, 0xFF);
SERIAL.print((char) ee);
}
return STK_OK;
}

void read_page() {
char result = (char)STK_FAILED;
int length = 256 * getch();
length += getch();
char memtype = getch();
if (CRC_EOP != getch()) {
error++;
SERIAL.print((char) STK_NOSYNC);
return;
}
SERIAL.print((char) STK_INSYNC);
if (memtype == ‘F’) result = flash_read_page(length);
if (memtype == ‘E’) result = eeprom_read_page(length);
SERIAL.print(result);
}

void read_signature() {
if (CRC_EOP != getch()) {
error++;
SERIAL.print((char) STK_NOSYNC);
return;
}
SERIAL.print((char) STK_INSYNC);
uint8_t high = spi_transaction(0x30, 0x00, 0x00, 0x00);
SERIAL.print((char) high);
uint8_t middle = spi_transaction(0x30, 0x00, 0x01, 0x00);
SERIAL.print((char) middle);
uint8_t low = spi_transaction(0x30, 0x00, 0x02, 0x00);
SERIAL.print((char) low);
SERIAL.print((char) STK_OK);
}
//////////////////////////////////////////
//////////////////////////////////////////

////////////////////////////////////
////////////////////////////////////
void avrisp() {
uint8_t ch = getch();
switch (ch) {
case ‘0’: // signon
error = 0;
empty_reply();
break;
case ‘1’:
if (getch() == CRC_EOP) {
SERIAL.print((char) STK_INSYNC);
SERIAL.print(“AVR ISP”);
SERIAL.print((char) STK_OK);
}
else {
error++;
SERIAL.print((char) STK_NOSYNC);
}
break;
case ‘A’:
get_version(getch());
break;
case ‘B’:
fill(20);
set_parameters();
empty_reply();
break;
case ‘E’: // extended parameters – ignore for now
fill(5);
empty_reply();
break;
case ‘P’:
if (!pmode)
start_pmode();
empty_reply();
break;
case ‘U’: // set address (word)
here = getch();
here += 256 * getch();
empty_reply();
break;

case 0x60: //STK_PROG_FLASH
getch(); // low addr
getch(); // high addr
empty_reply();
break;
case 0x61: //STK_PROG_DATA
getch(); // data
empty_reply();
break;

case 0x64: //STK_PROG_PAGE
program_page();
break;

case 0x74: //STK_READ_PAGE ‘t’
read_page();
break;

case ‘V’: //0x56
universal();
break;
case ‘Q’: //0x51
error = 0;
end_pmode();
empty_reply();
break;

case 0x75: //STK_READ_SIGN ‘u’
read_signature();
break;

// expecting a command, not CRC_EOP
// this is how we can get back in sync
case CRC_EOP:
error++;
SERIAL.print((char) STK_NOSYNC);
break;

// anything else we will return STK_UNKNOWN
default:
error++;
if (CRC_EOP == getch())
SERIAL.print((char)STK_UNKNOWN);
else
SERIAL.print((char)STK_NOSYNC);
}
}

Upload the Arduino ISP sketch which can be found an example into your Arduino Uno board. you can use any Arduino board but I am using Arduino Uno, after uploading this sketch your Arduino will act as a programmer.

ATtinny Connection with Arduino, Circuit diagram:

Now we will connect the ATtinny85 with the Arduino. Connect the pin eight of ATtinny85  to five volts of the Arduino UNO. Connect pin seven of the ATtinny85 to pin 13 of the Arduino Uno. Connect pin six of the ATtinny85 to pin 12 of the Arduino UNO. Connect pin 5 of the ATtinny85 to pin 11 of the Arduino UNO. Connect pin one of the ATtinny85  to pin 10 of the Arduino UNO and finally, pin four of the ATtinny85 Microcontroller to the ground pin of the Arduino UNO. Also do not forget to add 10uf capacitor with reset and ground.

For the programming we just need to put the ATtinny85 into the depth socket and then connect the Arduino UNO with our computer. Now after wiring go to the Tools menu and select ATtinny85:

Now change the clock to 8 megahertz:

Select the port change the programmer as Arduino as ISP

Then click on the burn bootloader you only have to burn the bootloader once.

Once I have connected an LED to pin five of the ATtinny85 which is pin d0.

Code:

Now after writing the code in the sketch we will upload the code to the Arduino as upload using programmer.

After uploading the program the led will start blinking.

ATtinnny85 Based Project:

Clap ON / OFF circuit using ATtinny85 microcontroller:

Now to make the this circuit we will repeat the same steps to program the ATtinny85 microcontroller with Arduino as discussed above and upload the code:

After uploading the code to the ATtinny85 microcontroller we will remove the ATtinny85 microcontroller from the Arduino. Now we will connect the ATtinny85 with sensor and relay module.

• Connect the pin number 7 of the ATtinny85 with the out of the sound sensor
• Connect the ground pin number 4 of the ATtinny85 with the ground of the sound sensor
• Connect the battery positive terminal with pin number 8 of the ATtinny85 and with VCC of the relay and sound sensor
• Connect the ground of the relay with the ground of the ATtinny85 which is pin number 4.

Now the circuit is completed and if we connect a bulb or other appliance with the relay it will turn on and off with the clap.