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The ADXL345 is a small, thin, low power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16g. Digital output data is formatted...
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ADXL345 on Analog.com

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Optimizing ADXL345 Settings for Movement Detection with Minimal Power Consumption



		

			

									
					    xOliveCi
					
							

			
				
									
											
			
			
				
    
			
			
			    	
			                    
                
				                on Jul 3, 2024 
				
			
			
		
    

				
		
    
		    		    
		    
		    		      		            		        
    Category: Software
    
    		        		            		    
    Product Number:  ADXL345  
    
    		        		    		    	
			
    Hi,
    

    We are using the ADXL345 accelerometer in our project to detect the movement of equipment, with an emphasis on minimizing power consumption. We do not need to detect impacts such as taps or double taps, just the regular movement of the device that contains this sensor.
    

    Our primary goal is to adjust the ADXL345 settings to:
    

      

    • Exclusively detect actual movement of the equipment.
      • 

    • Significantly reduce power consumption by eliminating unnecessary detections and minimizing the sensor’s operational overhead.
      • 

    

    Currently, we are trying different configurations from the datasheet, specifically positions 0x2C to 0x2F, corresponding to:
    

      

    • BW_RATE = 0x2C
      • 

    • POWER_CTL = 0x2D
      • 

    • INT_ENABLE = 0x2E
      • 

    • INT_MAP = 0x2F
      • 

    

    Could you please advise on the best settings or configurations to achieve these objectives? Specifically, we are looking for ways to fine-tune the sensitivity and potentially deactivate functions that detect impacts, focusing solely on movement detection.
    

    We appreciate any detailed guidance or recommendations you can provide to help us optimize the use of the ADXL345 for our specific needs.
    

    I have attached the program file we are using for testing.
    

    Thank you for your support.
    

    Thanks!
    


    ADXL345_TESTS.zip
    
										

    
				Fix ADXL version...
    
[edited by: xOliveCi at 3:16 PM (GMT -4) on 3 Jul 2024]
				
    
						
			        
		
    

				
						
        

    
    Tags: 
                                            
                 software
                
                                                    
                 accelerometers
                
                                                    
                 Sensors and MEMS
                
                                                    
                 adxl345
                
                                
            
    
    
    

		
    
			
						
									
									
						
						
			
			
			
			
		
    

        
        

					
    
			
    


    


	
    
		






		

			
    
			
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      Hi  
      

      

      Thank you for posting your question on EZ. If I understand correctly, you can set the "DATA-READY" interrupts for your application (do not need to set up the activity, tap,...). (Please find…
      
				
			
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      •  Analog Employees  
      
            
			                            
                                                                                                                        
            
				
			
            
					
      
	
      

		
		
      
					
      Hi  
      

      

      Thank you for posting your question on EZ. If I understand correctly, you can set the "DATA-READY" interrupts for your application (do not need to set up the activity, tap,...). (Please find attached file which is a MATLAB code to communicate with ADXL345 via NI USB-8452. It shows the registers, their value and sequence. Feel free to change it based on your desired value (range, ODR,...). 
      

      

      The power consumption can be reduced by activating the low power mode (at the expense of noise performance). Also, the ADXL345 automatically modulates its power consumption in proportion to its output data rate, as outlined in Table 7 of the datasheet. 
      

      

      Please let me know if you have any questions or my understanding of your problem/application is incorrect. 
      

      

      Regards,
      

      Mohammad
      


      



      
    
      
        Fullscreen
        ADXL345-I2C-DRDY.txt
        Download
    
      
    
      clear all
clc
close all

list = ni845xlist;
controllerList = ni845xlist;
ni845Obj = ni845x(controllerList.SerialNumber(1));
accelerometerAddress = scanI2CBus(ni845Obj);
adxlDevice = device(ni845Obj, 'I2CAddress', accelerometerAddress);

DeviceidRegisterAddress = 0x00;

% Enable data-ready interrupt (bit 7) in INT_ENABLE register (0x2E)
writeRegister(adxlDevice, 0x2E, 0x80);

% Map data-ready interrupt to INT1 (bit 0) in INT_MAP register (0x2F)
writeRegister(adxlDevice, 0x2F, 0x00);

% setting ODR and low-power mode
writeRegister(adxlDevice, 0x2C, 0x1B);

% data format
writeRegister(adxlDevice, 0x31, 0x8);

dataRegs = hex2dec('32'):hex2dec('37');

% Set the ADXL345 in measuring mode
writeRegister(adxlDevice, 0x2D, 8);

% Specify the number of samples to acquire
numSamples = 1000; % Change this to the desired number of samples


% Read acceleration data from ADXL345
sampleCount = 0;
while sampleCount < numSamples
    % Check if data-ready interrupt is active
     intSource = readRegister(adxlDevice, 0x30);
     dataReady = bitget(intSource, 8);
    % Check if new data is ready
     if dataReady==1
            
        % Read acceleration data
          accelerationData = readRegister(adxlDevice, 0x32, length(dataRegs), 'uint8');
          

        % Convert the raw data to signed 16-bit integers
        xAccraw = typecast(uint16(accelerationData(1) + bitshift(accelerationData(2), 8)), 'int16');
        yAccraw = typecast(uint16(accelerationData(3) + bitshift(accelerationData(4), 8)), 'int16');
        zAccraw = typecast(uint16(accelerationData(5) + bitshift(accelerationData(6), 8)), 'int16');

        % Scale the acceleration values
        scaleFactor = 3.9; % scale factor
        xAcc = xAccraw * scaleFactor;
        yAcc = yAccraw * scaleFactor;
        zAcc = zAccraw * scaleFactor;

        % Display the acceleration values
        fprintf('Acceleration - X: %.2f g, Y: %.2f g, Z: %.2f g\n', xAcc, yAcc, zAcc);


        sampleCount = sampleCount + 1;
        pause off;
    end
end

      

      


      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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      •  Analog Employees  
      
            
			                            
                                                                                                                        
            
				
			
            
					
      
	
      

		
		
      
					
      Hi  
      

      

      Thank you for posting your question on EZ. If I understand correctly, you can set the "DATA-READY" interrupts for your application (do not need to set up the activity, tap,...). (Please find attached file which is a MATLAB code to communicate with ADXL345 via NI USB-8452. It shows the registers, their value and sequence. Feel free to change it based on your desired value (range, ODR,...). 
      

      

      The power consumption can be reduced by activating the low power mode (at the expense of noise performance). Also, the ADXL345 automatically modulates its power consumption in proportion to its output data rate, as outlined in Table 7 of the datasheet. 
      

      

      Please let me know if you have any questions or my understanding of your problem/application is incorrect. 
      

      

      Regards,
      

      Mohammad
      


      



      
    
      
        Fullscreen
        ADXL345-I2C-DRDY.txt
        Download
    
      
    
      clear all
clc
close all

list = ni845xlist;
controllerList = ni845xlist;
ni845Obj = ni845x(controllerList.SerialNumber(1));
accelerometerAddress = scanI2CBus(ni845Obj);
adxlDevice = device(ni845Obj, 'I2CAddress', accelerometerAddress);

DeviceidRegisterAddress = 0x00;

% Enable data-ready interrupt (bit 7) in INT_ENABLE register (0x2E)
writeRegister(adxlDevice, 0x2E, 0x80);

% Map data-ready interrupt to INT1 (bit 0) in INT_MAP register (0x2F)
writeRegister(adxlDevice, 0x2F, 0x00);

% setting ODR and low-power mode
writeRegister(adxlDevice, 0x2C, 0x1B);

% data format
writeRegister(adxlDevice, 0x31, 0x8);

dataRegs = hex2dec('32'):hex2dec('37');

% Set the ADXL345 in measuring mode
writeRegister(adxlDevice, 0x2D, 8);

% Specify the number of samples to acquire
numSamples = 1000; % Change this to the desired number of samples


% Read acceleration data from ADXL345
sampleCount = 0;
while sampleCount < numSamples
    % Check if data-ready interrupt is active
     intSource = readRegister(adxlDevice, 0x30);
     dataReady = bitget(intSource, 8);
    % Check if new data is ready
     if dataReady==1
            
        % Read acceleration data
          accelerationData = readRegister(adxlDevice, 0x32, length(dataRegs), 'uint8');
          

        % Convert the raw data to signed 16-bit integers
        xAccraw = typecast(uint16(accelerationData(1) + bitshift(accelerationData(2), 8)), 'int16');
        yAccraw = typecast(uint16(accelerationData(3) + bitshift(accelerationData(4), 8)), 'int16');
        zAccraw = typecast(uint16(accelerationData(5) + bitshift(accelerationData(6), 8)), 'int16');

        % Scale the acceleration values
        scaleFactor = 3.9; % scale factor
        xAcc = xAccraw * scaleFactor;
        yAcc = yAccraw * scaleFactor;
        zAcc = zAccraw * scaleFactor;

        % Display the acceleration values
        fprintf('Acceleration - X: %.2f g, Y: %.2f g, Z: %.2f g\n', xAcc, yAcc, zAcc);


        sampleCount = sampleCount + 1;
        pause off;
    end
end

      

      


      
			
      

		
			
	      

		
		
	
      
	
      
		
      
			
		
      
	
      
	
      
		
						
						
				
						
				
				
		
		
      
			
		
      
	
      

      

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