SparkFun Electronics - Triple Axis Accelerometer Breakout

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Triple Axis Accelerometer Breakout - ADXL345

sku: SEN-09156

Description: Breakout board for the Analog Device ADXL345. The ADXL345 is a small, thin, low power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I2C digital interface.

The ADXL345 is well suited to measures the static acceleration of gravity in tilt-sensing applications, as well as dynamic acceleration resulting from motion or shock. Its high resolution (4 mg/LSB) enables measurement of inclination changes less than 1.0°.

Several special sensing functions are provided. Activity and inactivity sensing detect the presence or lack of motion and if the acceleration on any axis exceeds a user-set level. Tap sensing detects single and double taps. Free-fall sensing detects if the device is falling. These functions can be mapped to one of two interrupt output pins. An integrated, patent pending 32-level first in, first out (FIFO) buffer can be used to store data to minimize host processor intervention. Low power modes enable intelligent motion-based power management with threshold sensing and active acceleration measurement at extremely low power dissipation.

Features:

2.0-3.6VDC Supply Voltage
Ultra Low Power: 40uA in measurement mode, 0.1uA in standby@ 2.5V
Tap/Double Tap Detection
Free-Fall Detection
SPI and I2C interfaces

Documents:

Pricing

	126 in stock backorder allowed

$27.95	price
$25.16	10-99 (10% off)
$22.36	100+ (20% off)

	quantity

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Comments

22 comments

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	by tz +2.3 \| August 20, 2009 at 9:19 AM 0
I just got one and can't seem to make it work, at least in I2C mode, with an Arduino - either with the Wire library or using a separate short program. I can't even read the ID register - it gets hung up after sending the address. I've verified the timing (as far as I can without a scope - all the registers are working and the code is derived from some 2 wire eeprom code known to work).

	by EyeTic +2 \| October 23, 2009 at 4:29 PM 0
I've plugged it in according to the schematic and the datasheet like this: scheme01 but it shorted. I've narrowed down the shorting wires to these: scheme02 Any idea if the chip is defective or is it my wiring that is wrong?

+2.3

| August 20, 2009 at 9:37 AM

To clarify, this is with both an Arduino Pro and Lily Pad (at 3.3v), the right pins (4 wires, +.-,sda,scl - cs and adsel high) with pull-ups (Tried 330, 2k, and a few others). - I get an ACK from the address (0x3a as selected).

Since I don't have an example of known good code (for clock rate) I can't really tell if the part is broken or if I'm just doing something wrong which is specific to this part or something subtle. I can't find any code examples specific to this part. Does anyone have this working (using the I2C, but I'll probably try the SPI just to verify it works if I must)

	by viliam \| August 20, 2009 at 12:42 AM
I haven't used this part with I2C, but the posted sample code should get you started with SPI. It's written in C but it should point you in the right direction for how to write your arduino sketch.

+2.3

| August 24, 2009 at 0:37 AM

I wrote a sketch that outputs at 57600. Read the Wire lib info for what the calls do.

It uses the "pull to ground" address of 0x1d. I.e. CS and AD are grounded, SCK goes to A5, SDA to A4, with 3.3 and ground to the arduino pins.

(I originally missed a few things including apparently you need to turn on pullups on the AVR - A checklist would help)

This board limits comment length so I can't upload it here.

Rsimonton

+1.6

| August 28, 2009 at 1:02 PM

+0.15

I have been working with the XL345 and a Parallax Propeller controller. It's been frustrating to say the least. I am programming in assembly using two wire SPI to communicate. I have been able, at times, to consistently return a device ID and also data from the X-axis, but no sooner does it start to make sense and then nothing. I have been through my timing code to ensure I have a symmetric clock signal and it looks correct. This has also been done without a scope though. It is weird, it will start working for no apparent reason, then I continue working on my code and then it just quits. My clock is at about 2Mhz, which should work, but I will slow it down and see what it does. The documentation from AD could have used some more examples!

	by dimkasta +1.6 \| September 10, 2009 at 5:10 PM 0
Also the datasheet is a bit vague on the actual resolution settings. Does it work with 16bit resolution @+-2g ?

	by Rsimonton +1.6 \| September 12, 2009 at 7:55 AM 0
As I interpret the docs, the 2g mode is always 10 bit. In the high res mode 4g is 11 bit, 8g is 12 bit and 16g is 13 bit. This gives you a consistent resolution over the entire range. The g values are plus and minus and the data is two's complement so you are losing one bit for a sign.

	by tz +2.3 \| September 22, 2009 at 12:00 AM 0
Next update could you do one non-cantilevered? (The data sheet says it is a bad idea) It could fit the standard 0.7 inch breadboarding, sockets, etc.and have 4 pins each side and be much more stable. (Also if you could add some unpopulated SMD resistor pads to pull up the I2C, and/or have solder jumpers to pull up CS and SA so I could do I2C by just running 4 wires).

	by EyeTic +2 \| September 25, 2009 at 11:37 AM 0
I just got this, did anyone find some Arduino/Processing code for this thing? Would be very helpful. Thanks

	by tz +2.3 \| October 15, 2009 at 11:20 PM 0
at my blog, harleyhacking, I have some example code that uses a 3.3v (8mhz) arduino to read the chip at the maximum rate of 3.2khz (13 bits, 3 axes). http://harleyhacking.blogspot.com/2009/10/adxl345-at-full-speed-32khz-on-arduino.html

	by EyeTic +2 \| October 23, 2009 at 9:20 AM 0
tz, thanx for the code. I'm not sure how to use C code with the Arduino, I was hoping for a piece of authentic Arduino code or at least a point in the right direction. I'm kinda lost, I'm not even sure I have the wiring right (I'm trying to I2C communicate with the chip). Thanx

	by lond +1 \| October 16, 2009 at 1:29 PM 0
I have used the break out board for a couple of weeks now, and I had no problem to access it via i2c after setting up the right right registers.

	by lgg2 +1.3 \| October 17, 2009 at 4:41 PM 0
Hello, I am having also problems with it. In I2C mode, sometimes is working, sending data, and stops, later continue. Other times it doesn't work nothing (this breakout). An EEPROM in the same bus work without problems... The same in two boards: - ArduinoNANO 5v + ShiftLevel - ATmega328p 3.3v + FT232RL Breakout Internals pull-ups disabled. External: 4k7, 1k, 10k and nothing. Any idea?

lgg2

+1.3

| October 17, 2009 at 5:54 PM

Hello again,

A desesperted try and... works. The problem (in my case) seems to be the SCK pin. It seems to be "not_soldered_as_must" and after a fe minutes of work, went to fail. Giving heat with the soldier and pushing a bit in that area can work.

If some one try this, be careful. The board pad can disappear easy (in my case, with several times over the same area, happened, and it is no easy make a bridge over).

tHNKS

davev

+4.2

| November 16, 2009 at 5:26 PM

//Arduino I2C ADXL345 example code
//Dave Vondle, 11/16/09

#include

#define X0 0x32
#define X1 0x33
#define Y0 0x34
#define Y1 0x35
#define Z0 0x36
#define Z1 0x37

void setup()
{
Wire.begin(); // join i2c bus
Serial.begin(19200); // start serial for output

Wire.beginTransmission(0x1D); // transmit to ADXL345
Wire.send(0x2D);// POWER_CTL
Wire.send(0x09);// measurement mode, 4hz wakeup
Wire.endTransmission(); // stop transmitting
}

void loop()
{
Serial.print(getDir('x'), DEC); // print as an ASCII-encoded decimal
Serial.print("t"); // prints a tab
Serial.print(getDir('y'), DEC);
Serial.print("t");
Serial.print(getDir('z'), DEC);
Serial.print("t");
Serial.println(""); // prints a newline
delay(300);

}

byte requestByte(char dir){
Wire.beginTransmission(0x1D); // transmit to ADXL345
Wire.send(dir);
Wire.endTransmission(); // stop transmitting
Wire.requestFrom(0x1D, 1); // request 1 byte from ADXL345
while(Wire.available()){
return(Wire.receive()); //
}
}

int getDir(char dir){
int var;

if(dir=='x'){
var=requestByte(X0);
var=var+(requestByte(X1)<<8);
}else if(dir=='y'){
var=requestByte(Y0);
var=var+(requestByte(Y1)<<8);
}else if(dir=='z'){
var=requestByte(Z0);
var=var+(requestByte(Z1)<<8);
}
return(var);
}

	by davev +4.2 \| November 16, 2009 at 5:28 PM 0
in the above code after "#include" write: (less than sign)wire.h(greater than sign)

	by Olfox +1.1 \| November 23, 2009 at 6:30 AM 0
Before buying this module, Do you think that I can use Two axes ( x and y ) to mesures the tilling of a mobile and the third axe to mesure the acceleration o f this mobile? Thanks a lot !

Sondergaard

| December 4, 2009 at 10:25 PM

This module has just two 0.1 uF decoupling capacitors, BUT the AD documentation suggests much heavier noise isolation -- 10 uF and 0.1 uF in parallel AFTER a resistance up to 100 ohms.

Turns out AD is not kidding. I had terrible problems with inconsistent behavior until adding 10 uF decoupling and inserting a 27-ohm resistor in series with the 2.8V power supply I was using.

I am still having trouble talking to the blasted thing via SPI, can't get the expected device-id value out, but at least the behavior is now consistent.

Those having trouble with this breakout board might want to try adding this heavy-duty decoupling/isolation in accordance with AD recommendations! Wow what a finicky part.

Sondergaard

| December 5, 2009 at 7:20 PM

WARNING!

It would appear that the ADXL345 SDO line -- at least when configured for 4-wire SPI, the only configuration I'm testing -- is VERY SENSITIVE TO RINGING.

I STRONGLY RECOMMEND applications insert a damping resistor in series with the ADXL345 SDO line. I used 27 ohms here to solve the problem.

Before this fix, I could not get the correct device ID response. Pressing my thumb all over the breakout board changed the device ID response and sometimes made it OK. After much gnashing of teeth I finally discovered this issue.

	by Wolf12886 +2.1 \| December 13, 2009 at 0:14 AM 0
If anyone else is having trouble getting this board working in i2c mode, make sure you've got a pull-up on the SD0 line. It took me a few hours of debugging to figure out that SD0 was floating low and causing the chip to switch to its alt address.

Sondergaard

| December 20, 2009 at 11:46 AM

To follow up on my two earlier comments regarding sensitivity to noise and ringing: apparently there was some RFI getting into my circuit as well as the power and ringing problems I experienced. A solid ground is essential. Again, this is running 4-wire SPI on 2.7V digital power.

This really is the most finicky part I have ever used. It doesn't take much to make it misbehave by not receiving and/or sending SPI data as expected. But with the extra power filtering, the damping resistor on the SPI output line, and a solid ground with limited RFI pickup, it finally seems to be happy.