different pin assignment of I2C on pro mini

Hello guys,

im using an ADXL345 sensor to measure acceleration in my system.
im using the stock Adafruit ADXL345 lib to read data from the sensor using the included "SensorTest" example, and its working well and data is read on the serial port:

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

/* Assign a unique ID to this sensor at the same time */
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);

void displaySensorDetails(void)
{
  sensor_t sensor;
  accel.getSensor(&sensor);
  Serial.println("------------------------------------");
  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println(" m/s^2");
  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println(" m/s^2");
  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" m/s^2");  
  Serial.println("------------------------------------");
  Serial.println("");
  delay(500);
}

void displayDataRate(void)
{
  Serial.print  ("Data Rate:    "); 
  
  switch(accel.getDataRate())
  {
    case ADXL345_DATARATE_3200_HZ:
      Serial.print  ("3200 "); 
      break;
    case ADXL345_DATARATE_1600_HZ:
      Serial.print  ("1600 "); 
      break;
    case ADXL345_DATARATE_800_HZ:
      Serial.print  ("800 "); 
      break;
    case ADXL345_DATARATE_400_HZ:
      Serial.print  ("400 "); 
      break;
    case ADXL345_DATARATE_200_HZ:
      Serial.print  ("200 "); 
      break;
    case ADXL345_DATARATE_100_HZ:
      Serial.print  ("100 "); 
      break;
    case ADXL345_DATARATE_50_HZ:
      Serial.print  ("50 "); 
      break;
    case ADXL345_DATARATE_25_HZ:
      Serial.print  ("25 "); 
      break;
    case ADXL345_DATARATE_12_5_HZ:
      Serial.print  ("12.5 "); 
      break;
    case ADXL345_DATARATE_6_25HZ:
      Serial.print  ("6.25 "); 
      break;
    case ADXL345_DATARATE_3_13_HZ:
      Serial.print  ("3.13 "); 
      break;
    case ADXL345_DATARATE_1_56_HZ:
      Serial.print  ("1.56 "); 
      break;
    case ADXL345_DATARATE_0_78_HZ:
      Serial.print  ("0.78 "); 
      break;
    case ADXL345_DATARATE_0_39_HZ:
      Serial.print  ("0.39 "); 
      break;
    case ADXL345_DATARATE_0_20_HZ:
      Serial.print  ("0.20 "); 
      break;
    case ADXL345_DATARATE_0_10_HZ:
      Serial.print  ("0.10 "); 
      break;
    default:
      Serial.print  ("???? "); 
      break;
  }  
  Serial.println(" Hz");  
}

void displayRange(void)
{
  Serial.print  ("Range:         +/- "); 
  
  switch(accel.getRange())
  {
    case ADXL345_RANGE_16_G:
      Serial.print  ("16 "); 
      break;
    case ADXL345_RANGE_8_G:
      Serial.print  ("8 "); 
      break;
    case ADXL345_RANGE_4_G:
      Serial.print  ("4 "); 
      break;
    case ADXL345_RANGE_2_G:
      Serial.print  ("2 "); 
      break;
    default:
      Serial.print  ("?? "); 
      break;
  }  
  Serial.println(" g");  
}

void setup(void) 
{
  Serial.begin(115200);
  Serial.println("Accelerometer Test"); Serial.println("");
    pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  delay(50);
  digitalWrite(10, LOW); // 0V
  digitalWrite(11, HIGH); // 5V
  
  /* Initialise the sensor */
  if(!accel.begin())
  {
    /* There was a problem detecting the ADXL345 ... check your connections */
    Serial.println("Ooops, no ADXL345 detected ... Check your wiring!");
    while(1);
  }

  /* Set the range to whatever is appropriate for your project */
  accel.setRange(ADXL345_RANGE_16_G);
  // displaySetRange(ADXL345_RANGE_8_G);
  // displaySetRange(ADXL345_RANGE_4_G);
  // displaySetRange(ADXL345_RANGE_2_G);
  
  /* Display some basic information on this sensor */
  displaySensorDetails();
  
  /* Display additional settings (outside the scope of sensor_t) */
  displayDataRate();
  displayRange();
  Serial.println("");
}

void loop(void) 
{
  /* Get a new sensor event */ 
  sensors_event_t event; 
  accel.getEvent(&event);
 
  /* Display the results (acceleration is measured in m/s^2) */
  Serial.print("X: "); Serial.print(event.acceleration.x); Serial.print("  ");
  Serial.print("Y: "); Serial.print(event.acceleration.y); Serial.print("  ");
  Serial.print("Z: "); Serial.print(event.acceleration.z); Serial.print("  ");Serial.println("m/s^2 ");
  delay(500);
}

what i would like to know is if anyone can help me understand wether its possible to change the lib's SCL to A3 and SDA to A2, because this will make the sensor super easy to install on a straight header pin row over the Pro mini, thus making everything firmer and more reliable.

see attached picture - it shows the issue clearly.

thanks for your help.

No, the I²C pins of the ATmega328P are fixed and can't be reassigned to other pins.

Pieter

PieterP:
No, the I²C pins of the ATmega328P are fixed and can't be reassigned to other pins.

Pieter

i read about a software I2C lib that can do it, but im trying to understand how to adopt the ADXL345 lib to it.

You could add some jumper wires to the board to move A4, A5 over to D2, D3, and (or A4/D3, A5/D2, whichever is needed) and then just leave D2, D3 as unused inputs (their default state).

Don't forget 3.3K or 4.7K pullup resistors if the module doesn't have them already.

i3dm:
i read about a software I2C lib that can do it, but im trying to understand how to adopt the ADXL345 lib to it.

You could of course do that, but it's a waste of time, IMHO, and the performance of bit-banging the I²C bus in software instead of using the hardware peripheral will be poorer.
I would just run a wire to pins A4-A5.

interesing idea to jumper the wires, ill try it, but it addes a bit more work to the assembly.
why do you think the software i2c is a waste of time? might work well in this application.
thanks.

why do you think the software i2c is a waste of time?

It is very slow.

i3dm:
why do you think the software i2c is a waste of time? might work well in this application.
thanks.

Software I2C is slow and inefficient. Editing the library takes much more time than simply running a wire to the right pins.