How to Test the MPU-6050 and ADXL345 Sensors on Smart Pi One (Python and C)¶

This guide explains how to connect and test the MPU-6050 and ADXL345 sensors with the Smart Pi One board using both Python (via the smartpi-mpu6050 package) and C. It also covers how to detect the sensors via I2C.

MPU-6050

1. Prerequisites¶

Hardware¶

Smart Pi One board
Jumper wires for connections
MPU-6050 sensor or ADXL345 sensor

Software¶

Python 3.6 or higher
smartpi-mpu6050 Python package
I2C enabled on the Smart Pi One
python3-smbus system library for I2C communication
libi2c-dev package for C development

2. Activating I2C on Smart Pi One (for MPU-6050 and ADXL345)¶

Before starting with sensor tests, ensure that I2C is enabled on the Smart Pi One. Follow these steps:

Open Armbian-Config via an SSH interface or terminal window:
```
sudo armbian-config
```
Choose System:
Select Hardware:
Enable i2c1, then Save and Back:
To finish, Reboot to apply the changes:

3. How to Test the MPU-6050 Sensor¶

Wiring Diagram¶

Connect the MPU-6050 sensor to the Smart Pi One using this setup:

MPU-6050 Pin	Smart Pi One Pin	Description
VCC	(1) 3.3V	Power
GND	(6) GND	Ground
SCL	(27) SCL (I2C1 Clock)	I2C Clock
SDA	(28) SDA (I2C1 Data)	I2C Data

Smart Pi One - MPU-6050 Wiring

Detecting the MPU-6050 Using I2C¶

Run the following step to verify that the MPU-6050 sensor is detected:

sudo i2cdetect -y 1

You should see the MPU-6050 detected at address 0x68.

MPU-6050

Using Python to Read MPU-6050 Data¶

Example Python Script for Testing MPU-6050:¶

Here’s a complete script to read MPU-6050 from the sensor:

from smartpi_mpu6050.mpu6050 import MPU6050

mpu = MPU6050(0x68)

temp = mpu.get_temp()
print(f"Temperature: {temp:.2f} °C")

accel_data = mpu.get_accel_data()
print(f"Accelerometer: X={accel_data['x']:.2f} m/s^2, Y={accel_data['y']:.2f} m/s^2, Z={accel_data['z']:.2f} m/s^2")

gyro_data = mpu.get_gyro_data()
print(f"Gyroscope: X={gyro_data['x']:.2f} °/s, Y={gyro_data['y']:.2f} °/s, Z={gyro_data['z']:.2f} °/s")

Creating and Running the Script¶

Prerequisites¶

Install the required system libraries for I2C communication:

sudo apt-get update
sudo apt-get install python3-smbus

Install the Python package:

sudo pip3 install smartpi-mpu6050

Open a text editor, such as nano, and create the Python file:
```
nano test_mpu6050.py
```
Paste the script into the file and save it.
Execute the script with the necessary permissions (you may need to use sudo):
```
sudo python3 test_mpu6050.py
```
You should see the temperature, accelerometer, and gyroscope data in the terminal.

Using a C Program to Read MPU-6050 Data¶

Example C Program¶

#include <stdio.h>
#include <linux/i2c-dev.h>
#include <i2c/smbus.h>  
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>

#define MPU6050_ADDR 0x68
#define PWR_MGMT_1   0x6B
#define ACCEL_XOUT0  0x3B
#define TEMP_OUT0    0x41

int read_word_2c(int fd, int reg) {
    int high = i2c_smbus_read_byte_data(fd, reg);
    int low = i2c_smbus_read_byte_data(fd, reg + 1);
    int val = (high << 8) + low;
    if (val >= 0x8000) {
        val = -(65535 - val + 1);
    }
    return val;
}

int main() {
    int fd;
    char *filename = (char*)"/dev/i2c-1";

    if ((fd = open(filename, O_RDWR)) < 0) {
        printf("Failed to open the i2c bus\n");
        return 1;
    }

    if (ioctl(fd, I2C_SLAVE, MPU6050_ADDR) < 0) {
        printf("Failed to acquire bus access and/or talk to slave\n");
        return 1;
    }

    i2c_smbus_write_byte_data(fd, PWR_MGMT_1, 0x00);

    int accel_x = read_word_2c(fd, ACCEL_XOUT0);
    int accel_y = read_word_2c(fd, ACCEL_XOUT0 + 2);
    int accel_z = read_word_2c(fd, ACCEL_XOUT0 + 4);

    int temp_raw = read_word_2c(fd, TEMP_OUT0);
    float temp = (temp_raw / 340.0) + 36.53;

    printf("Temperature: %.2f C\n", temp);
    printf("Accelerometer: X=%d Y=%d Z=%d\n", accel_x, accel_y, accel_z);

    close(fd);
    return 0;
}

Compilation and Execution¶

Prerequisites¶

Install the required I2C development library:

sudo apt-get install libi2c-dev

Open a text editor, such as nano, to create the C file:
```
nano test_mpu6050.c
```
Paste the C program into the file and save it.

Compile the program with

gcc -o test_mpu6050 test_mpu6050.c -li2c

Run the program:
```
./test_mpu6050
```
You should see the temperature and accelerometer data printed to the terminal.

4. How to Test the ADXL345 Sensor¶

ADXL345

Wiring Diagram¶

Connect the ADXL345 sensor to the Smart Pi One using this setup:

ADXL345 Pin	Smart Pi One Pin	Description
VCC	(1) 3.3V	Power
GND	(6)	Ground
SCL	(27) SCL (I2C1 Clock)	I2C Clock
SDA	(28) SDA (I2C1 Data)	I2C Data

Smart Pi One - ADXL345 Wiring

Detecting the ADXL345 Using I2C¶

Run the following step to verify that the ADXL345 sensor is detected:

sudo i2cdetect -y 1
 ```

You should see the ADXL345 detected at address `0x53`.

![MPU-6050](../../../img/SmartPi/Sensors&Modules/SmartPi_MPU-6050-ADXL345/SmartPi_MPU-6050_ADXL345_13.png)

### Using Python to Read ADXL345 Data

### Example Python Script for Testing ADXL345

Here’s a complete script to read data from the ADXL345 sensor:

```python
from smartpi_mpu6050.mpu6050 import MPU6050

adxl = MPU6050(0x53)

accel_data = adxl.get_accel_data()
print(f"Accelerometer: X={accel_data['x']:.2f} m/s^2, Y={accel_data['y']:.2f} m/s^2, Z={accel_data['z']:.2f} m/s^2")

Creating and Running the Script¶

Prerequisites¶

Install the required system libraries for I2C communication:

sudo apt-get update
sudo apt-get install python3-smbus

Install the Python package:

sudo pip3 install smartpi-mpu6050

Open a text editor, such as nano, and create the Python file:
```
nano test_adxl345.py
```
Paste the script into the file and save it.
Execute the script with the necessary permissions (you may need to use sudo):
```
sudo python3 test_adxl345.py
```
You should see the accelerometer data in the terminal.

Using a C Program to Read ADXL345 Data¶

Example C Program¶

#include <stdio.h>
#include <linux/i2c-dev.h>
#include <i2c/smbus.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <unistd.h>

#define ADXL345_ADDR 0x53
#define POWER_CTL     0x2D
#define DATA_FORMAT   0x31
#define DATAX0       0x32

int read_word_2c(int fd, int reg) {
    int low = i2c_smbus_read_byte_data(fd, reg);
    int high = i2c_smbus_read_byte_data(fd, reg + 1);
    int val = (high << 8) + low;
    return val;
}

int main() {
    int fd;
    char *filename = (char*)"/dev/i2c-1";

    if ((fd = open(filename, O_RDWR)) < 0) {
        printf("Failed to open the i2c bus\n");
        return 1;
    }

    if (ioctl(fd, I2C_SLAVE, ADXL345_ADDR) < 0) {
        printf("Failed to acquire bus access and/or talk to slave\n");
        return 1;
    }

    i2c_smbus_write_byte_data(fd, POWER_CTL, 0x08);  // Set the device to measure mode
    i2c_smbus_write_byte_data(fd, DATA_FORMAT, 0x00); // Set the range to +/- 2g

    int accel_x = read_word_2c(fd, DATAX0);
    int accel_y = read_word_2c(fd, DATAX0 + 2);
    int accel_z = read_word_2c(fd, DATAX0 + 4);

    printf("Accelerometer: X=%d Y=%d Z=%d\n", accel_x, accel_y, accel_z);

    close(fd);
    return 0;
}

Compilation and Execution¶

Prerequisites¶

Install the required I2C development library:

sudo apt-get install libi2c-dev

Example C Program Steps¶

Open a text editor, such as nano, to create the C file:
```
nano test_adxl345.c
```
Paste the C program into the file and save it.

Compile the program with:

gcc -o test_adxl345 test_adxl345.c -li2c

Run the program:
```
./test_adxl345
```
You should see the accelerometer data printed in the terminal.

5. Troubleshooting¶

Common Issues:¶

I2C Device Not Detected
Ensure I2C is enabled on the Smart Pi One using sudo armbian-config.
Verify the connections of the SDA and SCL pins.
Use the following command to check if the MPU-6050 or ADXL345

is detected:

sudo i2cdetect -y 1

- You should see the address 0x68 (or 0x53 for ADXL345) in the output.

No Data from Sensor
Ensure the correct I2C address (0x68 (or 0x53 for ADXL345)) is being used in the code.
Check power and ground connections.
Library Installation Issues
Ensure that python3-smbus or libi2c-dev is installed, depending on the language you're using.