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VL53L0X.py
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VL53L0X.py
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# The MIT License (MIT)
#
# Copyright (c) 2017 Tony DiCola for Adafruit Industries
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`adafruit_vl53l0x`
====================================================
CircuitPython driver for the VL53L0X distance sensor. This code is adapted
from the pololu driver here:
https://github.com/pololu/vl53l0x-arduino
See usage in the examples/vl53l0x_simpletest.py file.
* Author(s): Tony DiCola
Implementation Notes
--------------------
**Hardware:**
* Adafruit `VL53L0X Time of Flight Distance Sensor - ~30 to 1000mm
<https://www.adafruit.com/product/3317>`_ (Product ID: 3317)
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the ESP8622 and M0-based boards:
https://github.com/adafruit/circuitpython/releases
* Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
"""
import math
import time
import adafruit_bus_device.i2c_device as i2c_device
from micropython import const
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_VL53L0X.git"
# Configuration constants:
# pylint: disable=bad-whitespace
_SYSRANGE_START = const(0x00)
_SYSTEM_THRESH_HIGH = const(0x0C)
_SYSTEM_THRESH_LOW = const(0x0E)
_SYSTEM_SEQUENCE_CONFIG = const(0x01)
_SYSTEM_RANGE_CONFIG = const(0x09)
_SYSTEM_INTERMEASUREMENT_PERIOD = const(0x04)
_SYSTEM_INTERRUPT_CONFIG_GPIO = const(0x0A)
_GPIO_HV_MUX_ACTIVE_HIGH = const(0x84)
_SYSTEM_INTERRUPT_CLEAR = const(0x0B)
_RESULT_INTERRUPT_STATUS = const(0x13)
_RESULT_RANGE_STATUS = const(0x14)
_RESULT_CORE_AMBIENT_WINDOW_EVENTS_RTN = const(0xBC)
_RESULT_CORE_RANGING_TOTAL_EVENTS_RTN = const(0xC0)
_RESULT_CORE_AMBIENT_WINDOW_EVENTS_REF = const(0xD0)
_RESULT_CORE_RANGING_TOTAL_EVENTS_REF = const(0xD4)
_RESULT_PEAK_SIGNAL_RATE_REF = const(0xB6)
_ALGO_PART_TO_PART_RANGE_OFFSET_MM = const(0x28)
_I2C_SLAVE_DEVICE_ADDRESS = const(0x8A)
_MSRC_CONFIG_CONTROL = const(0x60)
_PRE_RANGE_CONFIG_MIN_SNR = const(0x27)
_PRE_RANGE_CONFIG_VALID_PHASE_LOW = const(0x56)
_PRE_RANGE_CONFIG_VALID_PHASE_HIGH = const(0x57)
_PRE_RANGE_MIN_COUNT_RATE_RTN_LIMIT = const(0x64)
_FINAL_RANGE_CONFIG_MIN_SNR = const(0x67)
_FINAL_RANGE_CONFIG_VALID_PHASE_LOW = const(0x47)
_FINAL_RANGE_CONFIG_VALID_PHASE_HIGH = const(0x48)
_FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT = const(0x44)
_PRE_RANGE_CONFIG_SIGMA_THRESH_HI = const(0x61)
_PRE_RANGE_CONFIG_SIGMA_THRESH_LO = const(0x62)
_PRE_RANGE_CONFIG_VCSEL_PERIOD = const(0x50)
_PRE_RANGE_CONFIG_TIMEOUT_MACROP_HI = const(0x51)
_PRE_RANGE_CONFIG_TIMEOUT_MACROP_LO = const(0x52)
_SYSTEM_HISTOGRAM_BIN = const(0x81)
_HISTOGRAM_CONFIG_INITIAL_PHASE_SELECT = const(0x33)
_HISTOGRAM_CONFIG_READOUT_CTRL = const(0x55)
_FINAL_RANGE_CONFIG_VCSEL_PERIOD = const(0x70)
_FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI = const(0x71)
_FINAL_RANGE_CONFIG_TIMEOUT_MACROP_LO = const(0x72)
_CROSSTALK_COMPENSATION_PEAK_RATE_MCPS = const(0x20)
_MSRC_CONFIG_TIMEOUT_MACROP = const(0x46)
_SOFT_RESET_GO2_SOFT_RESET_N = const(0xBF)
_IDENTIFICATION_MODEL_ID = const(0xC0)
_IDENTIFICATION_REVISION_ID = const(0xC2)
_OSC_CALIBRATE_VAL = const(0xF8)
_GLOBAL_CONFIG_VCSEL_WIDTH = const(0x32)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_0 = const(0xB0)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_1 = const(0xB1)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_2 = const(0xB2)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_3 = const(0xB3)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_4 = const(0xB4)
_GLOBAL_CONFIG_SPAD_ENABLES_REF_5 = const(0xB5)
_GLOBAL_CONFIG_REF_EN_START_SELECT = const(0xB6)
_DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD = const(0x4E)
_DYNAMIC_SPAD_REF_EN_START_OFFSET = const(0x4F)
_POWER_MANAGEMENT_GO1_POWER_FORCE = const(0x80)
_VHV_CONFIG_PAD_SCL_SDA__EXTSUP_HV = const(0x89)
_ALGO_PHASECAL_LIM = const(0x30)
_ALGO_PHASECAL_CONFIG_TIMEOUT = const(0x30)
_VCSEL_PERIOD_PRE_RANGE = const(0)
_VCSEL_PERIOD_FINAL_RANGE = const(1)
# pylint: enable=bad-whitespace
def _decode_timeout(val):
# format: "(LSByte * 2^MSByte) + 1"
return float(val & 0xFF) * math.pow(2.0, ((val & 0xFF00) >> 8)) + 1
def _encode_timeout(timeout_mclks):
# format: "(LSByte * 2^MSByte) + 1"
timeout_mclks = int(timeout_mclks) & 0xFFFF
ls_byte = 0
ms_byte = 0
if timeout_mclks > 0:
ls_byte = timeout_mclks - 1
while ls_byte > 255:
ls_byte >>= 1
ms_byte += 1
return ((ms_byte << 8) | (ls_byte & 0xFF)) & 0xFFFF
return 0
def _timeout_mclks_to_microseconds(timeout_period_mclks, vcsel_period_pclks):
macro_period_ns = (((2304 * (vcsel_period_pclks) * 1655) + 500) // 1000)
return ((timeout_period_mclks * macro_period_ns) + (macro_period_ns // 2)) // 1000
def _timeout_microseconds_to_mclks(timeout_period_us, vcsel_period_pclks):
macro_period_ns = (((2304 * (vcsel_period_pclks) * 1655) + 500) // 1000)
return ((timeout_period_us * 1000) + (macro_period_ns // 2)) // macro_period_ns
class VL53L0X:
"""Driver for the VL53L0X distance sensor."""
# Class-level buffer for reading and writing data with the sensor.
# This reduces memory allocations but means the code is not re-entrant or
# thread safe!
_BUFFER = bytearray(3)
def __init__(self, i2c, address=41, io_timeout_s=0):
# pylint: disable=too-many-statements
self._device = i2c_device.I2CDevice(i2c, address)
self.io_timeout_s = io_timeout_s
# Check identification registers for expected values.
# From section 3.2 of the datasheet.
if (self._read_u8(0xC0) != 0xEE or self._read_u8(0xC1) != 0xAA or
self._read_u8(0xC2) != 0x10):
raise RuntimeError('Failed to find expected ID register values. Check wiring!')
# Initialize access to the sensor. This is based on the logic from:
# https://github.com/pololu/vl53l0x-arduino/blob/master/VL53L0X.cpp
# Set I2C standard mode.
for pair in ((0x88, 0x00), (0x80, 0x01), (0xFF, 0x01), (0x00, 0x00)):
self._write_u8(pair[0], pair[1])
self._stop_variable = self._read_u8(0x91)
for pair in ((0x00, 0x01), (0xFF, 0x00), (0x80, 0x00)):
self._write_u8(pair[0], pair[1])
# disable SIGNAL_RATE_MSRC (bit 1) and SIGNAL_RATE_PRE_RANGE (bit 4)
# limit checks
config_control = self._read_u8(_MSRC_CONFIG_CONTROL) | 0x12
self._write_u8(_MSRC_CONFIG_CONTROL, config_control)
# set final range signal rate limit to 0.25 MCPS (million counts per
# second)
self.signal_rate_limit = 0.25
self._write_u8(_SYSTEM_SEQUENCE_CONFIG, 0xFF)
spad_count, spad_is_aperture = self._get_spad_info()
# The SPAD map (RefGoodSpadMap) is read by
# VL53L0X_get_info_from_device() in the API, but the same data seems to
# be more easily readable from GLOBAL_CONFIG_SPAD_ENABLES_REF_0 through
# _6, so read it from there.
ref_spad_map = bytearray(7)
ref_spad_map[0] = _GLOBAL_CONFIG_SPAD_ENABLES_REF_0
with self._device:
self._device.write(ref_spad_map, end=1)
self._device.readinto(ref_spad_map, start=1)
for pair in ((0xFF, 0x01),
(_DYNAMIC_SPAD_REF_EN_START_OFFSET, 0x00),
(_DYNAMIC_SPAD_NUM_REQUESTED_REF_SPAD, 0x2C),
(0xFF, 0x00),
(_GLOBAL_CONFIG_REF_EN_START_SELECT, 0xB4)):
self._write_u8(pair[0], pair[1])
first_spad_to_enable = 12 if spad_is_aperture else 0
spads_enabled = 0
for i in range(48):
if i < first_spad_to_enable or spads_enabled == spad_count:
# This bit is lower than the first one that should be enabled,
# or (reference_spad_count) bits have already been enabled, so
# zero this bit.
ref_spad_map[1 + (i // 8)] &= ~(1 << (i % 8))
elif (ref_spad_map[1 + (i // 8)] >> (i % 8)) & 0x1 > 0:
spads_enabled += 1
with self._device:
self._device.write(ref_spad_map)
for pair in ((0xFF, 0x01), (0x00, 0x00), (0xFF, 0x00), (0x09, 0x00),
(0x10, 0x00), (0x11, 0x00), (0x24, 0x01), (0x25, 0xFF),
(0x75, 0x00), (0xFF, 0x01), (0x4E, 0x2C), (0x48, 0x00),
(0x30, 0x20), (0xFF, 0x00), (0x30, 0x09), (0x54, 0x00),
(0x31, 0x04), (0x32, 0x03), (0x40, 0x83), (0x46, 0x25),
(0x60, 0x00), (0x27, 0x00), (0x50, 0x06), (0x51, 0x00),
(0x52, 0x96), (0x56, 0x08), (0x57, 0x30), (0x61, 0x00),
(0x62, 0x00), (0x64, 0x00), (0x65, 0x00), (0x66, 0xA0),
(0xFF, 0x01), (0x22, 0x32), (0x47, 0x14), (0x49, 0xFF),
(0x4A, 0x00), (0xFF, 0x00), (0x7A, 0x0A), (0x7B, 0x00),
(0x78, 0x21), (0xFF, 0x01), (0x23, 0x34), (0x42, 0x00),
(0x44, 0xFF), (0x45, 0x26), (0x46, 0x05), (0x40, 0x40),
(0x0E, 0x06), (0x20, 0x1A), (0x43, 0x40), (0xFF, 0x00),
(0x34, 0x03), (0x35, 0x44), (0xFF, 0x01), (0x31, 0x04),
(0x4B, 0x09), (0x4C, 0x05), (0x4D, 0x04), (0xFF, 0x00),
(0x44, 0x00), (0x45, 0x20), (0x47, 0x08), (0x48, 0x28),
(0x67, 0x00), (0x70, 0x04), (0x71, 0x01), (0x72, 0xFE),
(0x76, 0x00), (0x77, 0x00), (0xFF, 0x01), (0x0D, 0x01),
(0xFF, 0x00), (0x80, 0x01), (0x01, 0xF8), (0xFF, 0x01),
(0x8E, 0x01), (0x00, 0x01), (0xFF, 0x00), (0x80, 0x00)):
self._write_u8(pair[0], pair[1])
self._write_u8(_SYSTEM_INTERRUPT_CONFIG_GPIO, 0x04)
gpio_hv_mux_active_high = self._read_u8(_GPIO_HV_MUX_ACTIVE_HIGH)
self._write_u8(_GPIO_HV_MUX_ACTIVE_HIGH,
gpio_hv_mux_active_high & ~0x10) # active low
self._write_u8(_SYSTEM_INTERRUPT_CLEAR, 0x01)
self._measurement_timing_budget_us = self.measurement_timing_budget
self._write_u8(_SYSTEM_SEQUENCE_CONFIG, 0xE8)
self.measurement_timing_budget = self._measurement_timing_budget_us
self._write_u8(_SYSTEM_SEQUENCE_CONFIG, 0x01)
self._perform_single_ref_calibration(0x40)
self._write_u8(_SYSTEM_SEQUENCE_CONFIG, 0x02)
self._perform_single_ref_calibration(0x00)
# "restore the previous Sequence Config"
self._write_u8(_SYSTEM_SEQUENCE_CONFIG, 0xE8)
def _read_u8(self, address):
# Read an 8-bit unsigned value from the specified 8-bit address.
with self._device:
self._BUFFER[0] = address & 0xFF
self._device.write(self._BUFFER, end=1)
self._device.readinto(self._BUFFER, end=1)
return self._BUFFER[0]
def _read_u16(self, address):
# Read a 16-bit BE unsigned value from the specified 8-bit address.
with self._device:
self._BUFFER[0] = address & 0xFF
self._device.write(self._BUFFER, end=1)
self._device.readinto(self._BUFFER)
return (self._BUFFER[0] << 8) | self._BUFFER[1]
def _write_u8(self, address, val):
# Write an 8-bit unsigned value to the specified 8-bit address.
with self._device:
self._BUFFER[0] = address & 0xFF
self._BUFFER[1] = val & 0xFF
self._device.write(self._BUFFER, end=2)
def _write_u16(self, address, val):
# Write a 16-bit BE unsigned value to the specified 8-bit address.
with self._device:
self._BUFFER[0] = address & 0xFF
self._BUFFER[1] = (val >> 8) & 0xFF
self._BUFFER[2] = val & 0xFF
self._device.write(self._BUFFER)
def _get_spad_info(self):
# Get reference SPAD count and type, returned as a 2-tuple of
# count and boolean is_aperture. Based on code from:
# https://github.com/pololu/vl53l0x-arduino/blob/master/VL53L0X.cpp
for pair in ((0x80, 0x01), (0xFF, 0x01), (0x00, 0x00), (0xFF, 0x06)):
self._write_u8(pair[0], pair[1])
self._write_u8(0x83, self._read_u8(0x83) | 0x04)
for pair in ((0xFF, 0x07), (0x81, 0x01), (0x80, 0x01),
(0x94, 0x6b), (0x83, 0x00)):
self._write_u8(pair[0], pair[1])
start = time.monotonic()
while self._read_u8(0x83) == 0x00:
if self.io_timeout_s > 0 and \
(time.monotonic() - start) >= self.io_timeout_s:
raise RuntimeError('Timeout waiting for VL53L0X!')
self._write_u8(0x83, 0x01)
tmp = self._read_u8(0x92)
count = tmp & 0x7F
is_aperture = ((tmp >> 7) & 0x01) == 1
for pair in ((0x81, 0x00), (0xFF, 0x06)):
self._write_u8(pair[0], pair[1])
self._write_u8(0x83, self._read_u8(0x83) & ~0x04)
for pair in ((0xFF, 0x01), (0x00, 0x01), (0xFF, 0x00), (0x80, 0x00)):
self._write_u8(pair[0], pair[1])
return (count, is_aperture)
def _perform_single_ref_calibration(self, vhv_init_byte):
# based on VL53L0X_perform_single_ref_calibration() from ST API.
self._write_u8(_SYSRANGE_START, 0x01 | vhv_init_byte & 0xFF)
start = time.monotonic()
while (self._read_u8(_RESULT_INTERRUPT_STATUS) & 0x07) == 0:
if self.io_timeout_s > 0 and \
(time.monotonic() - start) >= self.io_timeout_s:
raise RuntimeError('Timeout waiting for VL53L0X!')
self._write_u8(_SYSTEM_INTERRUPT_CLEAR, 0x01)
self._write_u8(_SYSRANGE_START, 0x00)
def _get_vcsel_pulse_period(self, vcsel_period_type):
# pylint: disable=no-else-return
# Disable should be removed when refactor can be tested
if vcsel_period_type == _VCSEL_PERIOD_PRE_RANGE:
val = self._read_u8(_PRE_RANGE_CONFIG_VCSEL_PERIOD)
return (((val) + 1) & 0xFF) << 1
elif vcsel_period_type == _VCSEL_PERIOD_FINAL_RANGE:
val = self._read_u8(_FINAL_RANGE_CONFIG_VCSEL_PERIOD)
return (((val) + 1) & 0xFF) << 1
return 255
def _get_sequence_step_enables(self):
# based on VL53L0X_GetSequenceStepEnables() from ST API
sequence_config = self._read_u8(_SYSTEM_SEQUENCE_CONFIG)
# pylint: disable=bad-whitespace
tcc = (sequence_config >> 4) & 0x1 > 0
dss = (sequence_config >> 3) & 0x1 > 0
msrc = (sequence_config >> 2) & 0x1 > 0
pre_range = (sequence_config >> 6) & 0x1 > 0
final_range = (sequence_config >> 7) & 0x1 > 0
return (tcc, dss, msrc, pre_range, final_range)
def _get_sequence_step_timeouts(self, pre_range):
# based on get_sequence_step_timeout() from ST API but modified by
# pololu here:
# https://github.com/pololu/vl53l0x-arduino/blob/master/VL53L0X.cpp
pre_range_vcsel_period_pclks = self._get_vcsel_pulse_period(_VCSEL_PERIOD_PRE_RANGE)
msrc_dss_tcc_mclks = (self._read_u8(_MSRC_CONFIG_TIMEOUT_MACROP) + 1) & 0xFF
msrc_dss_tcc_us = _timeout_mclks_to_microseconds(
msrc_dss_tcc_mclks, pre_range_vcsel_period_pclks)
pre_range_mclks = _decode_timeout(self._read_u16(_PRE_RANGE_CONFIG_TIMEOUT_MACROP_HI))
pre_range_us = _timeout_mclks_to_microseconds(pre_range_mclks, pre_range_vcsel_period_pclks)
final_range_vcsel_period_pclks = self._get_vcsel_pulse_period(_VCSEL_PERIOD_FINAL_RANGE)
final_range_mclks = _decode_timeout(self._read_u16(_FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI))
if pre_range:
final_range_mclks -= pre_range_mclks
final_range_us = _timeout_mclks_to_microseconds(
final_range_mclks, final_range_vcsel_period_pclks)
return (msrc_dss_tcc_us,
pre_range_us,
final_range_us,
final_range_vcsel_period_pclks,
pre_range_mclks)
@property
def signal_rate_limit(self):
"""The signal rate limit in mega counts per second."""
val = self._read_u16(_FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT)
# Return value converted from 16-bit 9.7 fixed point to float.
return val / (1 << 7)
@signal_rate_limit.setter
def signal_rate_limit(self, val):
assert 0.0 <= val <= 511.99
# Convert to 16-bit 9.7 fixed point value from a float.
val = int(val * (1 << 7))
self._write_u16(_FINAL_RANGE_CONFIG_MIN_COUNT_RATE_RTN_LIMIT, val)
@property
def measurement_timing_budget(self):
"""The measurement timing budget in microseconds."""
budget_us = 1910 + 960 # Start overhead + end overhead.
tcc, dss, msrc, pre_range, final_range = self._get_sequence_step_enables()
step_timeouts = self._get_sequence_step_timeouts(pre_range)
msrc_dss_tcc_us, pre_range_us, final_range_us, _, _ = step_timeouts
if tcc:
budget_us += (msrc_dss_tcc_us + 590)
if dss:
budget_us += 2*(msrc_dss_tcc_us + 690)
elif msrc:
budget_us += (msrc_dss_tcc_us + 660)
if pre_range:
budget_us += (pre_range_us + 660)
if final_range:
budget_us += (final_range_us + 550)
self._measurement_timing_budget_us = budget_us
return budget_us
@measurement_timing_budget.setter
def measurement_timing_budget(self, budget_us):
# pylint: disable=too-many-locals
assert budget_us >= 20000
used_budget_us = 1320 + 960 # Start (diff from get) + end overhead
tcc, dss, msrc, pre_range, final_range = self._get_sequence_step_enables()
step_timeouts = self._get_sequence_step_timeouts(pre_range)
msrc_dss_tcc_us, pre_range_us, _ = step_timeouts[:3]
final_range_vcsel_period_pclks, pre_range_mclks = step_timeouts[3:]
if tcc:
used_budget_us += (msrc_dss_tcc_us + 590)
if dss:
used_budget_us += 2*(msrc_dss_tcc_us + 690)
elif msrc:
used_budget_us += (msrc_dss_tcc_us + 660)
if pre_range:
used_budget_us += (pre_range_us + 660)
if final_range:
used_budget_us += 550
# "Note that the final range timeout is determined by the timing
# budget and the sum of all other timeouts within the sequence.
# If there is no room for the final range timeout, then an error
# will be set. Otherwise the remaining time will be applied to
# the final range."
if used_budget_us > budget_us:
raise ValueError('Requested timeout too big.')
final_range_timeout_us = budget_us - used_budget_us
final_range_timeout_mclks = _timeout_microseconds_to_mclks(
final_range_timeout_us,
final_range_vcsel_period_pclks)
if pre_range:
final_range_timeout_mclks += pre_range_mclks
self._write_u16(_FINAL_RANGE_CONFIG_TIMEOUT_MACROP_HI,
_encode_timeout(final_range_timeout_mclks))
self._measurement_timing_budget_us = budget_us
@property
def range(self):
"""Perform a single reading of the range for an object in front of
the sensor and return the distance in millimeters.
"""
# Adapted from readRangeSingleMillimeters &
# readRangeContinuousMillimeters in pololu code at:
# https://github.com/pololu/vl53l0x-arduino/blob/master/VL53L0X.cpp
for pair in ((0x80, 0x01), (0xFF, 0x01), (0x00, 0x00),
(0x91, self._stop_variable), (0x00, 0x01), (0xFF, 0x00),
(0x80, 0x00), (_SYSRANGE_START, 0x01)):
self._write_u8(pair[0], pair[1])
start = time.monotonic()
while (self._read_u8(_SYSRANGE_START) & 0x01) > 0:
if self.io_timeout_s > 0 and \
(time.monotonic() - start) >= self.io_timeout_s:
raise RuntimeError('Timeout waiting for VL53L0X!')
start = time.monotonic()
while (self._read_u8(_RESULT_INTERRUPT_STATUS) & 0x07) == 0:
if self.io_timeout_s > 0 and \
(time.monotonic() - start) >= self.io_timeout_s:
raise RuntimeError('Timeout waiting for VL53L0X!')
# assumptions: Linearity Corrective Gain is 1000 (default)
# fractional ranging is not enabled
range_mm = self._read_u16(_RESULT_RANGE_STATUS + 10)
self._write_u8(_SYSTEM_INTERRUPT_CLEAR, 0x01)
return range_mm