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I'm just getting started with electronics (with Arduino) and have bought this SunFounder accelerometer with part code ADXL345 from Amazon.

enter image description here

My problem is I can't find a datasheet anywhere from SunFounder for this part. I found this datasheet on SparkFun's website for an ADXL345, which seemed like it matched the part as the first few lines of the datasheet description matched exactly the description for the part description on Amazon ("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... etc")

But then I noticed that the pin layout diagram in the SparkFun datasheet doesn't match my part:

enter image description here

So my questions are (sorry, I'm really really new to electronics):

  • What does the part code for an electronic component (like ADXL345) actually mean if different manufacturers can produce chips that look different / different pins etc. but have the same part number?
  • Is it safe to use the datasheet from SparkFun for ADXL345 for an ADXL345 made by SunFounder or will there be subtle differences in how they work?

Thanks!

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    \$\begingroup\$ "SundFounder" doesn't make chips, they just solder them on cheap boards. If you have the data sheet for the chip, then the labels on the board and a little deduction or recognition of what else is on there is likely to be enough for most purposes. \$\endgroup\$ – Chris Stratton May 30 '16 at 11:08
  • \$\begingroup\$ Ah okay thanks, so it should in theory work exactly like the datasheet says, just with things physically arranged in different places? \$\endgroup\$ – James Allen May 30 '16 at 11:18
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    \$\begingroup\$ @JamesAllen - What exactly do you mean by: "I noticed that the pin layout diagram in the SparkFun datasheet doesn't match my part"? \$\endgroup\$ – SamGibson May 30 '16 at 11:45
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    \$\begingroup\$ You are (mis-)comparing different things. The chip pin layout is for the black IC in the middle of the blue PCBA. Your photo shows the IC does have the expected 14 pins. The "part" as you call it (actually a PCBA - PCB assembly) has 9 holes. You already have a good answer from @DaveTweed so I won't duplicate it. I'll just say that, without a datasheet on the PCBA, it's the buyer who has to reverse-engineer the connections between the 9 holes and the 14-pins of the ADXL345 IC, and its related connections, power supply, pull-ups etc. - easy for experienced folks; less easy for beginners :-( \$\endgroup\$ – SamGibson May 30 '16 at 16:29
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    \$\begingroup\$ Great, thanks @SamGibson this now makes a lot more sense, that's exactly what I was misunderstanding - I thought the wiring diagram was for the circuit board, not the chip on it. Thanks for clearing this up for me! \$\endgroup\$ – James Allen Jun 3 '16 at 14:00
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It looks to me like the wiring on the PCB matches the chip pinout that you show — why do you say that it does not?

In any case, ADXL345 is the part number of the chip itself, which is made by Analog Devices; get the datasheet from them.

It doesn't seem as though there's any documentation on the PCB itself, so it looks like you'll have to assume that the signal labels on its pads correspond to the pins with the same names on the chip. You may need to do some reverse-engineering to figure out exacly what all of the other parts they've added are doing. It looks like there's a 3-terminal regulator and some bypass capacitors on the left, and some pullup/pulldown/termination resistors and an LED for various signals on the right. This is why you should never buy a board that has no documentation.

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  • \$\begingroup\$ Thanks! It's just that the chip pin layout diagram seems to show 14 pins (including 3 grounds, a Vs and a Vddi/0) whereas my chip only has 9 pins (including only 1 ground, a 5v and a 3.3v) - I'm guessing from your answer these differences can be ignored? Is the 5V supposed to be Vs and 3.3V supposed to be Vddi/o? Sorry if I'm asking stupid things, just really inexperienced! \$\endgroup\$ – James Allen May 30 '16 at 15:47
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    \$\begingroup\$ The ADXL345 chip itself (the black rectangle in the middle of the board) DOES have 14 pins. The board it is mounted on only has 9 connection points. \$\endgroup\$ – Peter Bennett May 30 '16 at 16:19
  • \$\begingroup\$ Ah okay! Right, I didn't realise the pin diagram was for the chip, I thought it was for the whole circuit board. Things suddenly make a lot more sense! Thanks! \$\endgroup\$ – James Allen Jun 3 '16 at 13:59

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