Help on issues found in VL53LX API v1.2.8?

[AGreen]

I'm using the latest API version (1.2.8) available from the VL53L4CX product page.

In my project I have implemented an interface to set configurations or run calibrations.

I am also using this driver for both the VL53L4CD and VL53L4CX, since the driver seems to be universal for all VL53LX parts. Correct me if I'm wrong.

(Problem 1 )

I noticed the function VL53LX_PerformOffsetPerVcselCalibration(~) would hang seemingly at random calls.

Below is the block of code with the issue and a potential fix. After I changed it, I've had no issues running it.

while ((Status == VL53LX_ERROR_NONE) && (inloopcount < Max) && (inloopcount < OverMax)) {
 
Status = VL53LX_WaitMeasurementDataReady(Dev);
 
if (Status == VL53LX_ERROR_NONE)
 
Status = VL53LX_GetMultiRangingData(Dev, &RangingMeasurementData);
 
pRange = &(RangingMeasurementData.RangeData[0]);
 
goodmeas = (pRange->RangeStatus == VL53LX_RANGESTATUS_RANGE_VALID);
 
ics = pdev->ll_state.cfg_internal_stream_count;
 
if ((Status == VL53LX_ERROR_NONE) && goodmeas) {
 
if (ics & 0x01) {
 
sum_ranging_range_A += pRange->RangeMilliMeter;
 
offset_meas_range_A++;
 
} else {
 
sum_ranging_range_B += pRange->RangeMilliMeter;
 
offset_meas_range_B++;
 
}
 
// NOTE: COMMENT OUT / REMOVE
inloopcount = offset_meas_range_A + offset_meas_range_B;
 
}
 
Status = VL53LX_ClearInterruptAndStartMeasurement(Dev);
 
// NOTE: ADD THIS
inloopcount++;
 
}

(Problem 2)

In the function VL53LX_SetDistanceMode(~) it will return with an error if setting distance to SHORT if using a VL53L4CD (Close Distance). Is this correct behavior? It seems counterintuitive. I noted the line below where it checks the type.

VL53LX_Error VL53LX_SetDistanceMode(VL53LX_DEV Dev,
		VL53LX_DistanceModes DistanceMode)
{
	VL53LX_Error Status = VL53LX_ERROR_NONE;
	uint32_t inter_measurement_period_ms;
	uint32_t TimingBudget = 0;
	uint32_t MmTimeoutUs = 0;
	uint32_t PhaseCalTimeoutUs = 0;
 
	LOG_FUNCTION_START("%d", (int)DistanceMode);
 
	if ((DistanceMode != VL53LX_DISTANCEMODE_SHORT) &&
		(DistanceMode != VL53LX_DISTANCEMODE_MEDIUM) &&
		(DistanceMode != VL53LX_DISTANCEMODE_LONG))
		return VL53LX_ERROR_INVALID_PARAMS;
 
	if (IsL4(Dev) && (DistanceMode == VL53LX_DISTANCEMODE_SHORT)) // NOTE: This returns error for VL53L4CD (Close Distance)
		return VL53LX_ERROR_INVALID_PARAMS;
 
	inter_measurement_period_ms =  VL53LXDevDataGet(Dev,
				LLData.inter_measurement_period_ms);
 
	if (Status == VL53LX_ERROR_NONE)
		Status = VL53LX_get_timeouts_us(Dev, &PhaseCalTimeoutUs,
			&MmTimeoutUs, &TimingBudget);
 
	if (Status == VL53LX_ERROR_NONE)
		Status = SetPresetModeL3CX(Dev,
				DistanceMode,
				inter_measurement_period_ms);
 
	if (Status == VL53LX_ERROR_NONE) {
		VL53LXDevDataSet(Dev, CurrentParameters.DistanceMode,
				DistanceMode);
	}
 
	if (Status == VL53LX_ERROR_NONE) {
		Status = VL53LX_set_timeouts_us(Dev, PhaseCalTimeoutUs,
			MmTimeoutUs, TimingBudget);
 
		if (Status == VL53LX_ERROR_NONE)
			VL53LXDevDataSet(Dev, LLData.range_config_timeout_us,
				TimingBudget);
	}
 
	LOG_FUNCTION_END(Status);
	return Status;
}

Let me know what you think.

Regards,

Andrew

[John E KVAM · Accepted solution]

On the first one - I think you found a bug - thank you. I'm told my software guys will respond in a couple of days with a fix.

Why is there is no 'short' on the VL53L4CD (Close distance)??

Laser power is measured in power over time. So one can have a very intense light - as long as it's a very short pulse - or one can have a more dim light - but on for a longer time.

On the VL53L4CD, we chose a rather bright light - but that means we need a slower pulse repetition rate.

Turns out we already had that - it's just the medium distance mode. (The only difference between short, medium and long - is the pulse repetition rate.)

So do not 'invent' a short distance mode. Cranking up the pulse repetion rate will make the device non eye-safe. And one does not need it. There is plenty of light.

• john

[AGreen]

I'm glad I could help and thank you for clarifying how the distance mode works. I have the VL53L4CD working well in my project but I was just curious about that function.

Andrew