Problem with the iis328dq's data ready interrupt

[Luca Lorusso]

I'm trying to read the data from the iis328dq using the data ready function.

To do so, I wrote the CTRL_REG1 with 27h and CTRL_REG3 with 82h to have the accelerometer working in normal mode with 50 Hz of ODR. I use SPI at 25 Mbit/s to comunicate with the device.

I encountered 2 problems:

1)Initially no interrupts were generated from the accelerometer. Inserting a dummy read of the out registers after the power on of the accelerometer, I saw that the first interrupt was generated. Basically now reading every set of data multiple times the interrupts are generated until the accelerometer is powered down. Any idea why I see this behaviour?

2)Watching the interrupt line with an oscilloscope, I see that these interrupts are not generated at the ODR I set, but they are randomly generated.

[Miroslav BATEK]

First, the maximum communication speed is 10MHz.

When do you read the data? After Data ready interrupt is triggered?

[Luca Lorusso]

I didn't see that, I reduced the SPI speed, thanks.

The portion of code dedicated to the accelerometer is in one case of a switch.

Initially my idea was to read after every data ready interrupt so I put my read routine in an if which is executed only when a variable is changed in the callback function of the interrupt.

Now instead as soon I enter the case I do a dummy read and then there is the if activated by the interrupt where I read and save the data in an array. Without the dummy read, which is repeated every time that the switch is evaluated, I see no interrupts generated.

[Miroslav BATEK]

I think, you miss some interrupt, that is why you have to do the dummy read.

[Luca Lorusso]

I should see them with the oscilloscope if that was the case though. Instead if I try to execute the code without the dummy reads I actually don't see any commutation on the interrupt line.