Questions on Jetson Nano - Arduino i2c communication

Autonomous Machines Jetson & Embedded Systems Jetson Nano
3

Solved. I wired pins GND, 27 (SDA), 28 (SDL) to Arduino Nano GND, A4 (SDA), A5 (SCL) …

…and ran i2cdetect -y -r 0:

0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

Here’s my Python code (must first install smbus module with Python Pip):

import smbus
import time
# Nvidia Jetson Nano i2c Bus 0
bus = smbus.SMBus(0)

# This is the address we setup in the Arduino Program
address = 0x40

def writeNumber(value):
    bus.write_byte(address, value)
    # bus.write_byte_data(address, 0, value)
    return -1

def readNumber():
    number = bus.read_byte(address)
    # number = bus.read_byte_data(address, 1)
    return number

while True:
    var = input("")
    if not var:
        continue

    writeNumber(var)
    number = readNumber()

And the Arduino code, which simply instructs a Servo on Pin 3 to move 90 degrees clockwise or counterclockwise:

#include <Wire.h>
#include <Servo.h>

int i2cAddress = 0x40;

Servo myservo;  // create servo object to control a servo
// twelve servo objects can be created on most boards

//int pos = 0;    // variable to store the servo position

void setup()
{
  Wire.begin(i2cAddress);                // join i2c bus with address #0x40
  Wire.onReceive(receiveEvent); // register event
  Wire.onRequest(sendData);
  
  //Serial.begin(9600);           // start serial for output
  myservo.attach(3);  // attaches the servo on pin 3 to the servo object
  myservo.write(90);
}

int servoState = 0;

void receiveEvent(int bytes) {
  servoState = Wire.read();    // read one character from the I2C
}

void loop()
{
  if(servoState > 0) {  
    if(servoState == 2){
        myservo.write(90);
        servoState = 0;
    }
    else if(servoState == 3){    
        myservo.write(180);
        servoState = 0;                    
    }
  }
}

void sendData(){
    Wire.write(servoState);
}
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