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Fabian1
Fabian1
Associate
November 29, 2019
Question

VL53L1 UltraLite driver function VL53L1X_GetXtalk returns always 0

  • November 29, 2019
  • 5 replies
  • 1207 views

I am using the function VL53L1X_SetXtalk to set the crosstalk value. When I want to read back the crosstalk value with the function VL53L1X_GetXtal, this function returns always 0.

This topic has been closed for replies.

5 replies

Fabian1
Fabian1Author
Associate
December 3, 2019

I have further investigated this bug and I found out that the function VL53L1X_GetXtalk uses VL53L1_RdDWord for reading out the crosstalk value.

But what I see is that this register is only 16 bits wide. So I have changed two lines in the function VL53L1_GetXtalk and now it works:

uint16_t tmp;
status = VL53L1_RdWord(dev,ALGO__CROSSTALK_COMPENSATION_PLANE_OFFSET_KCPS,&tmp);

Could anyone else confirm this workaround?

John E KVAM
John E KVAM
ST Employee
December 19, 2019

​The latest software in the Ultra light driver contains your fix.

I'm guessing you were not the only one to find the bug.

VL53L1X_ERROR VL53L1X_GetXtalk(uint16_t dev, uint16_t *xtalk )
{
	VL53L1X_ERROR status = 0;
	uint32_t tmp;
 
	status = VL53L1_RdDWord(dev,ALGO__CROSSTALK_COMPENSATION_PLANE_OFFSET_KCPS, &tmp);
	*xtalk = (uint16_t)(tmp*1000)>>9; /* * 1000 to convert kcps to cps and >> 9 (7.9 format) */
	return status;
}

If this or any post solves your issue, please mark them as 'Accept as Solution' It really helps. And if you notice anything wrong do not hesitate to 'Report Inappropriate Content'. Someone will review it.
Hardwariano
Hardwariano
Associate III
September 29, 2020

Hello @John E KVAM​ ,

I have the same problem as @Fabian​ . That code doesn't work for me. After debugging and much trial and error, this is the code that works for me:

   

*xtalk = (uint16_t)((tmp*1000)>>25);

The reason I right shift 25 is that tmp is uint32_t and first 16 bits are zero. So 9 + 16 = 25:

tmp = b31 b30 b29 b28 b27 b26 b25 b24 b23 b22 b21 b20 b19 b18 b17 b16 0000 0000 0000 0000. Where:

  • [b31..b25] = Crosstalk value that matches the value calculated by VL53L1X_CalibrateXtalk().
  • [b24..b16] --> 9 bits shifted as ST API for VL53L1X indicates.
  • 0000 0000 0000 0000 --> 16 bits that I don't know where they come from, but must be shifted to get the correct crosstalk value from sensor internal's memory.

Am I right?

Regards

LWOEI.1
LWOEI.1
Associate
July 21, 2020

Hi Guys, a question here, i wonder if i install VL53l1X at shower room to detect falling , will it affected by steam or hot environment?

John E KVAM
John E KVAM
ST Employee
July 21, 2020

this is such a good question, I'm going to place it as a new query instead of putting it at the bottom a this thread.

If this or any post solves your issue, please mark them as 'Accept as Solution' It really helps. And if you notice anything wrong do not hesitate to 'Report Inappropriate Content'. Someone will review it.
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