Lesson 4 of 4

Talk I2C to an MPU-6050

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// Scan the I2C bus, then read the MPU-6050's WHO_AM_I register. #include <Wire.h> const byte MPU_ADDR = 0x68; // AD0 low: 0x68 const byte WHO_AM_I = 0x75; void setup() { pinMode(LED_BUILTIN, OUTPUT); Serial.begin(9600); Wire.begin(); // A4 = SDA, A5 = SCL byte found = 0; for (byte addr = 1; addr < 127; addr++) { Wire.beginTransmission(addr); if (Wire.endTransmission() == 0) { Serial.print("Found device at 0x"); Serial.println(addr, HEX); found++; } } Serial.print("Devices: "); Serial.println(found); Wire.beginTransmission(MPU_ADDR); Wire.write(WHO_AM_I); Wire.endTransmission(false); // keep the bus: repeated start Wire.requestFrom(MPU_ADDR, (byte)1); if (Wire.available()) { Serial.print("WHO_AM_I = 0x"); Serial.println(Wire.read(), HEX); } } void loop() { digitalWrite(LED_BUILTIN, HIGH); // heartbeat on L delay(500); digitalWrite(LED_BUILTIN, LOW); delay(500); }

Stopped · Your code isn't running yet. Until you press Run, the board runs the program already on it.

Nothing printed yet. Press Run.

I2C is a two-wire bus: SDA on A4 carries data, SCL on A5 the clock, and every device has an address. Scan the bus, find the MPU-6050 at 0x68, then ask it who it is.

Scan the I2C bus
Read a register with a repeated start
Print bytes in HEX

Pin	Connects to	What it does
`A4`	SDA	I2C data.
`A5`	SCL	I2C clock.
`5V`	VCC	Powers the breakout.
`GND`	GND	Common ground.

Wire it in

Sensors and actuators this board drives, with the real connections.

MPU-6050 IMUSupply 5 V
GY-521 breakout with an MPU-6050 at I2C address 0x68 (0x69 with AD0 high). Its own regulator lets it run from 5V; SDA goes to A4 and SCL to A5.
Part pin Board pin
VCC 5VWire colour red
GND GNDWire colour black
SCL A5Wire colour yellow
SDA A4Wire colour blue
Careful
The chip itself is 3.3 V. The breakout pulls SDA and SCL up to its 3.3 V, and Wire.begin() also turns on the 328P's weak pull-ups to 5 V, so the bus idles a little above 3.3 V. It works in practice; a level shifter is the clean fix.
SSD1306 OLED displaySupply 5 V
0.96 in 128 × 64 OLED at I2C address 0x3C, on A4 (SDA) and A5 (SCL).
Part pin Board pin
GND GNDWire colour black
VCC 5VWire colour red
SCL A5Wire colour yellow
SDA A4Wire colour blue
Careful
Read the pin order on the silk: some modules are GND VCC, others VCC GND, and swapping them kills the display. Its 1 KB frame buffer takes half the Nano's RAM, so keep text in flash with F("...").

All 10 parts on the Arduino Nano page

Connects to

What it does

A4

SDA

I2C data.

A5

SCL

I2C clock.

5V

VCC

Powers the breakout.

GND

GND

Common ground.

Wire it in

Sensors and actuators this board drives, with the real connections.

MPU-6050 IMUSupply 5 V

GY-521 breakout with an MPU-6050 at I2C address 0x68 (0x69 with AD0 high). Its own regulator lets it run from 5V; SDA goes to A4 and SCL to A5.

Part pin	Board pin
VCC	5VWire colour red
GND	GNDWire colour black
SCL	A5Wire colour yellow
SDA	A4Wire colour blue

Careful

The chip itself is 3.3 V. The breakout pulls SDA and SCL up to its 3.3 V, and Wire.begin() also turns on the 328P's weak pull-ups to 5 V, so the bus idles a little above 3.3 V. It works in practice; a level shifter is the clean fix.

SSD1306 OLED displaySupply 5 V

0.96 in 128 × 64 OLED at I2C address 0x3C, on A4 (SDA) and A5 (SCL).

Part pin	Board pin
GND	GNDWire colour black
VCC	5VWire colour red
SCL	A5Wire colour yellow
SDA	A4Wire colour blue

Careful

Read the pin order on the silk: some modules are GND VCC, others VCC GND, and swapping them kills the display. Its 1 KB frame buffer takes half the Nano's RAM, so keep text in flash with F("...").

All 10 parts on the Arduino Nano page

Talk I2C to an MPU-6050

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in

Talk I2C to an MPU-6050

Try it yourself

Serial monitor

Checks

Break it

Inputs

Parameters

Wire it in