Arduino - Jetson Nano i2c Communication Failure

Projects Programming
1

Hello,

I'm trying to create a communication between Arduino nano 33 IOT and the Jetson Nano. I'm using the i2c bus and I want to send a structure to the Jetson Nano but when I receive data over the bus it's gibberish.

Jetson Nano pins:
GND, 27 (SDA), 28 (SDL)
Arduino Nano 33 IoT pins:
GND, A4 (SDA), A5 (SCL)

Arduino code:

#include <Wire.h>           


int               i2cAddress         =       0x6a;
typedef struct {
  int         command;
  int         ack_Signature;                  
  int         x;
  int         y;
  int         z;                      
} JETSON_COMMANDS;

JETSON_COMMANDS SEND_CMD;
JETSON_COMMANDS RECEIVE_RESPONSE_CMD;



void setup() {
  // Setup the Serial
  Serial.begin(9600);
  while(!Serial) { ; }
  
  Wire.begin(i2cAddress);
  Wire.onReceive(receiveJetsonEvent);            
  Wire.onRequest(sendJetsonEvent);                
}

void loop() {
  SEND_CMD.command = 1;
  SEND_CMD.ack_Signature = 2;
  SEND_CMD.x = 3;
  SEND_CMD.y = 4;
  SEND_CMD.z = 2;
  sendJetsonEvent();
  Serial.println("SEND COMMAND");
  delay(5000);
}



void receiveJetsonEvent(int bytes) {
  Serial.println(bytes);
  Serial.println();
  Wire.readBytes((byte*) &RECEIVE_RESPONSE_CMD, sizeof RECEIVE_RESPONSE_CMD);
  Serial.println(RECEIVE_RESPONSE_CMD.command);
  Serial.println(RECEIVE_RESPONSE_CMD.ack_Signature);
  Serial.println(RECEIVE_RESPONSE_CMD.x);
  Serial.println(RECEIVE_RESPONSE_CMD.y);
  Serial.println(RECEIVE_RESPONSE_CMD.z);
  Serial.println("*******************************");
}
//            2. sendJetsonEvent()                 //
void sendJetsonEvent() {
  int count = Wire.write((byte*)& SEND_CMD, sizeof SEND_CMD);
  Serial.println(count);
}

Jetson Nano - Python3 code:

import struct
import time
import sambas
BINARY_FORMAT = '5h'

bus = sambas.SMBus(0)
address = 0x6a
def receiveArduinoEvent(num_of_bytes):
     data = bus.read_i2c_block_data(address, num_of_bytes)
     return data

while True:
     data = receiveArduinoEvent(20)
     data_struct = struct.unpack(BINARY_FORMAT, data)
     print(data)
     print(data[0])
     print(data[1])
     print(data[2])
     print(data[3])
     print(data[4])
     print('*******************')
     time.sleep(2)

My problem is that the struct library returns a TypeError: a bytes-like object is required, not 'list'
I would expect to receive a struct of 5 ints with the values 1,2,3,4,2

Can someone extend a helping hand?

Thank you!

2

What happens when you convert the list of bytes to a bytes object?

data_struct = struct.unpack(BINARY_FORMAT, bytes(data))
3

Hello @jfjlaros
Thank you,
your right, I need to cast the data object to byte.

4

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