Hello,
I have a question concerning "change of the I2c speed"
For my project i wired up a ADXL345 acc. sensor with an arduino Uno and an ethernet shield.
I use the SD card slot of the Ethernet shield to write the sensor data (xyz) to an SD card.
Unfortunately the sampling rate is to slow and i only achieve around 250 hz sampling rate.
I need around 1khz for dynamic measures.
I read about the possibility of changing the I2c speed from 100khz up to 400khz by changing
\Arduino\libraries\Wire\utility\twi.h
from
#ifndef TWI_FREQ
#define TWI_FREQ 100000L
#endif
to
#ifndef TWI_FREQ
#define TWI_FREQ 400000L
#endif
I did this, saved the file and restarted the Arduino IDE and did an upload of the code to my arduino.
Since i did this, the program stops in line
Serial.println("initializing the SD card..."); almost at the beginning of the setup part.
Does anyone know, if i have do change something else, or if I have to recompile the library?
I use a 2 m cable to connect the ADXL345 to the arduino
After changing the parameter back to 100khz everything is fine again.
In http://forum.arduino.cc/index.php/topic,16793.0.html the author says, you have
to delete
hardware/libraries/Wire/Wire.o
hardware/libraries/Wire/utility/twi.o
because the library must be re-compiled before it uses the new speed.
(This is done automaticaly when you open the Arduino-IDE)
but in my case, these files do not exist.
The code of my project:
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>
#include <SD.h>
unsigned long time;
File myFile;
/* Assign a unique ID to this sensor at the same time */
Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);
//void setDataRate(ADXL345_DATARATE_800HZ);
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(9600);
Serial.println("initializing the SD card...");
if (!SD.begin(4)) //selbstcheck aufruf SD.beginn i2c pin4
{
Serial.println("Initializing failed!!");
return;
}
Serial.println("Initializing completed");
Serial.println("Accelerometer Test");
Serial.println("");
/* 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);
accel.setDataRate(ADXL345_DATARATE_1600_HZ);
/* Display some basic information on this sensor */
displaySensorDetails();
/* Display additional settings (outside the scope of sensor_t) */
displayDataRate();
displayRange();
Serial.println("");
}
void loop(void)
{
unsigned long start=millis();
myFile = SD.open("logtest.csv", FILE_WRITE);
while (millis()-start<1000L)
{
/* Get a new sensor event */
sensors_event_t event;
accel.getEvent(&event);
time = millis();
/* write action to sd card, */
myFile.print(time);
myFile.print(" , ");
myFile.print(event.acceleration.x);
myFile.print(" , ");
myFile.print(event.acceleration.y);
myFile.print(" , ");
myFile.print(event.acceleration.z);
myFile.println(" ");
}
myFile.close();
}
Thanks a lot!