MPL3115A2 data ready interrupt issue

[paolog]

Hi everyone.

I have an issue with the interrupt generated by the sensor on data ready. Once in a while the interrupt is not generated, so the new reading from the sensor doesn't take place.

I followed some code samples, but still the interrupt is unreliable. Here are parts of my code:

Initialization

IIC_RegWrite(SlaveAddressIIC, CTRL_REG1, 0x04);
//delay
...
IIC_RegWrite(SlaveAddressIIC, CTRL_REG1, 0x80 | 0x18); // ALT_BIT, OSR8
IIC_RegWrite(SlaveAddressIIC, CTRL_REG2, 0x00);    
// Enable interrupt INT1 for data ready
IIC_RegWrite(SlaveAddressIIC, CTRL_REG3, 0x00); // Push/pull, active low
// INT_EN_DRDY_BIT is not enough to generate interrupt,
// INT_EN_PCHG_BIT must be also set
IIC_RegWrite(SlaveAddressIIC, CTRL_REG4, 0x80 | 0x02); // INT_EN_DRDY_BIT | INT_EN_PCHG_BIT
IIC_RegWrite(SlaveAddressIIC, CTRL_REG5, 0x80 | 0x02); // INT_EN_DRDY_BIT | INT_EN_PCHG_BIT - Interrupt su INT1
// DREM_BIT is not enough to generate interrupt,
// PDEFE_BIT must be also set
IIC_RegWrite(SlaveAddressIIC, PT_DATA_CFG_REG, 0x04 |0x02); // DREM_BIT | PDEFE_BIT

Start pressure acquisition 

// Enable data ready interrupt on GPIO pin
...
// Set OST
IIC_RegWrite(SlaveAddressIIC, CTRL_REG1, ALT_BIT | OSR_8 | OST_BIT);

ISR code clears MCU interrupt flag and sets a variable checked by main loop, where pressure reading is made as follows:

IIC_RegReadN(SlaveAddressIIC, 0x00, 5, (unsigned char *)mybuff);
// Convert readings
...

Data analyzer shows the correct communication between the MCU and sensor, with interrupt being generated and pressure reading performed. But once in a while the interrupt signal doesn't follow the request.

Any idea about the reason why this is happening? I'm currently using polling, but I would like to switch to a interrupt driven reading to reduce power consumption.

[JozefKozon · Accepted solution]

Hi Paolog,

please test an MPL3115A2 code attached, my colleague had created few years ago. It might help you to solve the issue.

With Best Regards,

Jozef

[paolog]

Hi Jozef, thank you for sharing the code.

I did some changes and the interrupt seems to be working fine now. This are the changes I did to my code:

1. Setting register PT_DATA_CFG_REG to 0x07 instead of 0x06 (all three bits DREM_BIT,  PDEFE_BIT and TDEFE_BIT are set, while I didn't set TDEFE_BIT), and moved the instruction before setting any of the other registers

2. Setting CTRL_REG4 and CTRL_REG5 to 0x80 instead of 0x82 (INT_EN_DRDY_BIT only, while I also set INT_EN_PCHG_BIT as it seemed like the interrupt wouldn't trigger without it)

I think that moving the instruction to set PT_DATA_CFG_REG in first place is the key, but well, code seems to be working fine and the analyzer always shows the interrupt now.

Thank you again.

Paolo