Unable to get LPS33 low pressure threshold to output to INT/DRDY pin.
Can someone help with the specific sequence to get the INT_DRDY output to become active when the pressure drops from the reference pressure by 156 hPA (120 mmHg).
I have read and reread the data sheet, and examined the ST "C" library source. I am able to configure the output pin for DRDY successfully.
The current sequence is outlined below. I've tried several different orders of the sequence. The pressure readings are correct in both value and timing. The INT_DRDY works correctly when configured as DRDY.
However, applying an external vacuum that is 3X the threshold setting does not cause the output to be active.
Thanks for your help in this matter.
Dave
1) Perform a software reset.
2) Initialize control registers 1 - 3. Here are some relevant bits:
REG.CTRL.REG1.ODR = 5; //Output data rate 75Hz
REG.CTRL.REG2.ONE_SHOT = 0; //Init to idle mode
REG.CTRL.REG3.INT_S = INT_S_P_Low; // Interrupt on pressure low
REG.CTRL.REG3.DRDY = 0; //Don't interrupt when data ready
REG.CTRL.REG3.F_OVR =0; //Dont interrupt on FIFO overrun
REG.CTRL.REG3.F_FTH =0; //Dont interrupt on FIFO threshold
REG.CTRL.REG3.F_FSS5 =0; //Dont interrupt in FIFO ready
REG.CTRL.REG3.PP_OD =0; //DRDY pin push pull
REG.CTRL.REG3.INT_H_L =0; //Interrupt active high
3)Check the WHOAMI register.
4)Set low power mode
5)Set the output data rate
6) Wait for 10 pressure samples
7) Set AUTOZERO
8) Wait two more samples.
9) Set the interrupt register :
INTReg.Bits.AUTORIFP = 0;
INTReg.Bits.RESET_ARP = 0;
INTReg.Bits.AUTOZERO = 0;
INTReg.Bits.RESET_AZ = 0;
INTRegCache->Bits.DIFF_EN = 1;
INTRegCache->Bits.PLE = 1;
INTRegCache->Bits.PHE = 1;
INTRegCache->Bits.LIR = 1;
10) Set the threshold register:
const unsigned short OverPthreshold = (unsigned short)((float)(60.f * 1.3f * 16.f));