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Fahad Mirza
Visitor II
November 17, 2017
Question

LIS2DE12 Interrupt on INT2 pad

  • November 17, 2017
  • 1 reply
  • 717 views
Posted on November 17, 2017 at 22:11

I am unable to generate an interrupt on INT2 pin. But I can generate an interrupt with the same configuration on INT1 pin. Seems like I am missing something obvious or the datasheet is missing something crucial!!

I am trying to detect a 180-degree flip from Z-axis. On a flat surface, Z-axis pointing upwards gives me approx +1g (decimal 65 with FS = 2). 180 flip will give me a negative value. Here is the configuration that worked on INT1 pin.

  • CTRL_REG1 = 0x5F  // ODR = 100Hz, LPen = 1, All axis enabled

  • CTRL_REG2 = 0x42  // Reference filtering, Filter data for AOI function on interrupt 2

  • REFERENCE = 50     // Taking the z-axis value close to 15

  • CTRL_REG3 = 0x20  // IA2 interrupt on INT1

  • CTRL_REG5 = 0x08 // Latch for INT1

  • CTRL_REG6 = 0

  • INT2_THS = 100 // A 180-degree flip gives me around -112 with REFERENCE 50

  • INT2_DURATION = 50 // 500ms with ODR=100Hz

  • INT2_CFG = 0x20 // Interrupt enable for High on Z-axis

With above configuration, I can detect the interrupt on INT1 pin. For INT2 pin I changed,

  • CTRL_REG3 = 0

  • CTRL_REG5 = 0x02 // Latch for INT2

  • CTRL_REG6 = 0x20 // IA2 interrupt on INT2 pin

...and I don't receive any interrupt. I just redirected the pin. This should work. Unless I am missing something obvious. Any help will be much appreciated.

#accelerometer #mems #interrupt
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    1 reply

    M
    Miroslav BATEK
    ST Employee
    November 20, 2017
    Posted on November 20, 2017 at 11:02

    You configuration is correct and it is working, but I see one small issue which probably makes the troubles.

    In the first case when the interrupt is directed to INT1 pin, you set 

    CTRL_REG5 = 0x08, this configuration set the Latch mode for the interrupt generator 1 not for the pin INT1. And because you are using interrupt generator 2 this settings is not used and the interrupt is not latched (returns back to 0 wen the boards is flipped back).

    When you direct the interrupt to INT2 you set CTRL_REG5 = 0x02, this configuration set the Latch mode for interrupt generator 2. As you are using this interrupt generator, the INT2 pit remains high until you read INT2_SRC register.

    I tried both case and the interrupt is triggered as you would expect but in second case I have to read the INT2_SRC register to clear the interrupt.

    F
    Fahad MirzaAuthor
    Visitor II
    November 21, 2017
    Posted on November 21, 2017 at 18:37

    I see. That makes sense. Let me try your suggestion.

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