I'm quite new to the world of electronics, and so I need some newbee-help. I've got an Arduino uno, and I've recently bought a LPR550AL pitch & roll gyro. (if it helps detailed info can be found here http://www.electrozone.dk/1550)

Obviously I read the description and the datasheet, but green as I am I don't trust that I understood it all properly. I'm uncertain about how I should interface the gyro with the arduino. The datasheets talks of external low- and high- pass filters which, quite frankly, I haven't a clue what means. Furthermore, the board has a 3,3 volt regulator which leaves me uncertain whether to use that or the arduinos 3,3 volt pin on the gyro-boards vin pin. The datasheet also mentions that I should short the selftest pin to ground, should I do that? The description says the same thing for the power down pin. I assume the power down pin will, well, power down the board? Can I even do that from one of the arduino pins? It occurs to me that they operate at 5 volts, and not 3,3.

Advice in general will be well received. Same goes for resources for further reading/learning. I should also be grateful if someone could give me instructions to connect this without burning anything :)

One final thing: Am I right in assuming that the difference between the vdd/3,3v input and VIN is that VIN is non-regulated?


1 Answer 1


Self-test pin: Going by the description page of your breakout board, seems this pin would already be connected to a pull-down resistor, which thus disables the self-test feature. You don't need to change anything here.

Power-down pin: Must be driven to GND for the LPR550AL to operate. So put a solder-short or a wire between the Power-down pin and the Ground pin next to it. But alternatively, if for some reason, you want to use this pin to trigger the LPR550AL's Power-On versus Low-Power state on the fly, you can connect it to an Arduino pin (in your code, be sure to enable the internal pull-up, then write a LOW on it for LPR550AL Power-On operation).

Low-pass filters on outputs are for noise reduction. Your board, as designed, seems to already have them, so the board is ready to go. This is clearly described on the page that you listed in your question; please read such details on your original breakout board product page as well as the datasheet of LPR550AL before asking these questions!

VIN is your non-regulated input, and VDD is the regulated 3.3V that also powers the LPR550AL on the board.

Circuit: If, for whatever reason, you need a reference for setting up your own circuit (instead of using the breakout board), you can refer to this circuit diagram for the same board (source: bottom of [this Pololu webpage](http://www.pololu.com/catalog/product/1266 )). The circuit doesn't look too difficult, and the suggested capacitor and resistor values are fairly common ones.

LPR550AL circuit

  • \$\begingroup\$ You're right. I should have been more thorough with reading the board details. \$\endgroup\$
    – Bladt
    Aug 26, 2012 at 9:12
  • \$\begingroup\$ Thank you for the highly explicit answer, that is a big help to me. Could I connect the power-down pin to the arduinos gournd, or will that not result in the same thing? I know it seems like a weird question, but that would be easier for me right now. Just to make sure; I can safely just connect the arduinos 3,3 V supply pin to the boards VDD (or VIN for that matter, since it's 3,3 V), the arduinos gnd to gnd on the board, and then an analogue input pin to the boards OUTX and/or OUTY pin? As long as power down is put to gnd of course. \$\endgroup\$
    – Bladt
    Aug 26, 2012 at 9:24
  • \$\begingroup\$ Here are two exercises for you: (#1) Read the Wikipedia article on Ground, then you can decide whether the two GNDs (Arduino's and the board's) can be connected, and even whether they MUST be connected. (#2) Put Arduino's 3.3V output into VIN and measure the voltage at VDD, that is put the PLUS of multimeter at VDD, and the MINUS of multimeter at GND, and take a voltage reading to see if the voltage is what is wanted. \$\endgroup\$
    – boardbite
    Aug 26, 2012 at 13:42
  • \$\begingroup\$ Ground on the arduino and ground on the breakout board must be connected. If I put 3,3 volts on VIN there will be 3,3 volts on VDD, this I know. \$\endgroup\$
    – Bladt
    Aug 27, 2012 at 0:20
  • \$\begingroup\$ (I still read the article and measured the voltage though). What I meant to ask was whether that is all I have to do, and whether it would make a difference to connect PD pin to gnd at another point :) I would assume not, but I'm not confident enough to say with with certainty that there is not some kind of anti-feedback circuitry on the board. (I also find it funny that the board has 2 gnd pins). I do appreciate the self-help approach you are taking though. Truly. \$\endgroup\$
    – Bladt
    Aug 27, 2012 at 0:27

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