LIS2DH 6D mode not working properly

[vcaia.1]

Hello,

I am trying to implement 6D mode. I am following 1:1 the code documented in the design tip DT0097.

I have been trying for a while: I2C interface is working and other modes of LIS2DH work properly.

As a safety measure, during the init I reset all registers back to their default value.

I read IRQ_SRC as soon as the INT1 line is raised.

However, the behavior is not as expected:

I do get interrupts when I move the board, but:

• If I move the board, I usually have 2 consecutive very near interrupts. The second is always with all the flags "low" set.
• The value in the flags is wrong: even with horizontal position I never get neutral X an Y, or even Z if I put the board in vertical
• The threshold, duration and registers seems to have no effect whatsoever
• If I rotate very slowly the board, I can succeed to flip it without triggering any interrupt

In the interrupt, I simply read INT1_SRC, that should be enough, right?

This is an example of events I get while flipping the Z axis of the board. Val is the (hex) value of INT1_SRC, while the rest is the string is my decoding of it.

Do you have any hint or fully-fledged example?

val:66 XU YD ZU

val:15 XD YD ZD

val:65 XD YD ZU

val:15 XD YD ZD

val:66 XU YD ZU

val:15 XD YD ZD

val:56 XU YD ZD

val:15 XD YD ZD

val:69 XD YU ZU

val:15 XD YD ZD

val:59 XD YU ZD

val:15 XD YD ZD

[Eleon BORLINI]

Hi @vcaia.1​ , you can refer to the LIS3DH application note for a further description of the 6D/4D orientation detection, even if the device is not exactly your LIS2DH (AN3308 p.28, LINK).

Can you please check if your are following the described steps in your code? Regards

[vcaia.1]

Thank you Eleon.

Yes, I read also that one document, it is not of any help.

This is my initalization code

void accel_flip_detection(void)
{
	uint8_t i2cdata[2];
	twi_master_init();
 
	ADDR = 0x30;
 
	i2cdata[0] = CTRL_REG5;
	i2cdata[1] = BOOT; 			//reset memory
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
		
	i2cdata[0] = CTRL_REG1;
	i2cdata[1] = 0x00;			//Stop
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
		
	i2cdata[0] = CTRL_REG2;
	i2cdata[1] = 0x00;			//default
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
		
	//CTRL_REG3
	i2cdata[0] = CTRL_REG3;
	i2cdata[1] = I1_AOI1;									// AOI1 interrupt generation is	routed to INT1 pin.
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);	
 
	//CTRL_REG4
	i2cdata[0] = CTRL_REG4;
	i2cdata[1] = 0; //+-2g
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);	
 
	i2cdata[0] = CTRL_REG5;
	i2cdata[1] = 0x00;			
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	i2cdata[0] = CTRL_REG6;
	i2cdata[1] = 0x00;			//default
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	//INT1_CFG -> interrupts on INT1
	i2cdata[0] = INT1_CFG;
	i2cdata[1] = AOI | d6D | ZHIE | ZLIE | YHIE | YLIE | XHIE | XLIE;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	uint8_t ths = 0x21;
	i2cdata[0] = INT1_THS;
	i2cdata[1] = ths;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	uint8_t duration = 0x20;
	i2cdata[0] = INT1_DURATION;
	i2cdata[1] = duration;
 twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
		
 //not needed, added as safety measure
	i2cdata[0] = REFERENCE;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);						//write address to read
 
	i2cdata[0] = FIFO_CTRL_REG;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	i2cdata[0] = 0x34;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x35;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x36;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x37;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x38;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3a;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3b;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3c;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3d;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3e;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
	i2cdata[0] = 0x3f;
	i2cdata[1] = 0x00;
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
 
	//CTRL_REG1 start Low power
	i2cdata[0] = CTRL_REG1;
	i2cdata[1] = ODR_25 | LPen | Zen | Yen | Xen;			// Set LIS3DH to low power mode with ODR = 25Hz.
	twi_master_transfer(ADDR | WRITE, i2cdata, 2, true);
 
	delay_ms(1);
}

And this is the ISR routine

void ACCEL_releaseInt1(void)
{
	static uint8_t last_orientation = 0x00;
	uint8_t i2cdata[2];
	ADDR = 0x30;
	twi_master_init();
 
	i2cdata[0] = INT1_SRC;
	twi_master_transfer(ADDR | WRITE, i2cdata, 1, false);
	twi_master_transfer(ADDR | READ, i2cdata, 1, true);
	uint8_t ir = (i2cdata[0] & 0b00111111); //current orientation
 
//	0b000100, //a
//	0b000010, //b
//	0b000001, //c
//	0b001000, //d
//	0b100000, //e
//	0b010000 //f
 
	char str[10];
	if (ir != last_orientation)
	{
		PRu8hex(str, i2cdata[0]);
		uart_putstring_buf((uint8_t*)"val:");
		uart_putstring_buf((uint8_t*)str);
 
		if (ir & 0b000010)
			uart_putstring_buf((uint8_t*)" XU");
		else if (ir & 0b000001)
			uart_putstring_buf((uint8_t*)" XD");
		else
			uart_putstring_buf((uint8_t*)" X-");
 
		if (ir & 0b0001000)
			uart_putstring_buf((uint8_t*)" YU");
		else if (ir & 0b000100)
			uart_putstring_buf((uint8_t*)" YD");
		else
			uart_putstring_buf((uint8_t*)" Y-");
 
		if (ir & 0b100000)
			uart_putstring_buf((uint8_t*)" ZU");
		else if (ir & 0b10000)
			uart_putstring_buf((uint8_t*)" ZD");
		else
			uart_putstring_buf((uint8_t*)" Z-");
 
		uart_putstring_buf((uint8_t*)"\n");
	}
 
	last_orientation = ir;
}

But I tried dozen of different combinations with no better outcome...

[vcaia.1]

Good morning,

I tried to achieve the same result doing a simple inertial wake up on axis z, as per the application note you posted. So, I expect an interrupt when axis Z value is above a certain value (so the board is laying on one of the two faces).

The results are the same: I get 2 IRQs every time, and the INT1_SRC doesn't show the real condition. It's almost like hp filter is active, because I always end up with lower poart of INT1_SRC = 0x15 (all the "low" IRQs).

[Eleon BORLINI]

Hi @vcaia.1​ , thank you for the detailed analysis. Can you try with modifying the interrupt duration? You can do it either latching the interrupt, i.e. setting to '1' the LIR_INT1 of the CTRL_REG5 (24h) register or directly changing the duration of the interrupt itself, by modifying the register content in the INT1_DURATION (33h) register. Regards

[vcaia.1]

I tried that, but I tried again now based on my code posted above.

LIR_INT1 has no effect, I see no difference.

Duration is already 0x20. (that should be 1280ms @25hz). Even if I put that one to 0x7f (5s!)I see no increased delay between events.

I understand the duration register as the time the event has to last in order to trigger the interrupt (e.g. the Z axis must be > the threshold for 5s) is it correct?

Or is it just the duration of the pulse on INT1 and it's enough to have one sample over the threshold?