ST VL53L7CH User manual

Introduction
The purpose of this user manual is to explain how to handle the VL53L7CH and VL53L8CH Time-of-Flight (ToF) sensors, using
the ultra light driver (ULD) API. It describes the main functions to program the device, the calibrations, and the output results.
The CNH data transform STMicroelectronics Time-of-Flight ranging sensor into a versatile optical sensor, which can enable
endless AI-based applications. This CNH raw data sent to the host, on top of the standard ranging data, opens the door to many
new applications beyond simple distance measurements. From solid material (carpet, wood, glass, mirror...) to gas or liquid
(water, oil, chemical...), it becomes possible to detect the location and the size of a cup in a coffee machine or beverage
dispenser, to sense the floor material for robotics, and develop advanced shape, motion, or hand posture recognition.
Figure 1. VL53L7CH and VL53L8CH sensor modules
References
VL53L7CH datasheet (DS14309)
VL53L8CH datasheet (DS14310)
A guide for using the artificial intelligence enabler VL53L7CH and VL53L8CH
multizone Time-of-Flight (ToF) sensors
UM3183
User manual
UM3183 - Rev 1 - June 2023
For further information contact your local STMicroelectronics sales office.
www.st.com

1 Acronyms and abbreviations
Acronym/abbreviation Definition
CNH compact normalized histogram
DOE diffractive optical element
FoV field of view
I2C inter-integrated circuit (serial bus)
Kcps/SPAD Kilo-count per second per SPAD (unit used to quantify the
number of photons into the SPAD array)
RAM random access memory
SCL serial clock line
SDA serial data
SPAD single photon avalanche diode
ToF Time-of-Flight
ULD ultra lite driver
VCSEL vertical-cavity surface-emitting diode
Xtalk crosstalk
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Acronyms and abbreviations
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2 Functional description
2.1 System overview
The system is composed of a hardware module and the ultra light driver software (VL53LMZ ULD) running on a
host (see figure below). The hardware module contains the ToF sensor. STMicroelectronics delivers the software
driver, which is referred to in this document as "the driver". This document describes the functions of the driver,
which are accessible to the host. These functions control the sensor and get the ranging data.
Figure 2. System overview
2.2 Effective orientation
The module includes a lens over the Rx aperture, which flips (horizontally and vertically) the captured image of
the target. Consequently, the zone identified as zone 0, in the bottom left of the SPAD array, is illuminated by a
target located at the top right-hand side of the scene.
Figure 3. Module effective orientation
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Functional description
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2.3 Schematics and I2C/SPI configuration
The communication between driver and firmware is handled by the I2C for both sensors, with a maximum speed
of 1 MHz. In addition, the VL53L8CH also has the possibility to communicate with SPI. In this case, the maximum
SPI speed is 3 MHz. The implementation of each communication protocol requires pull-ups as described in the
product datasheets.
The devices have a default I2C address of 0x52. However, it is possible to change the default address to avoid
conflicts with other devices, or to facilitate adding multiple modules to the system for a greater system FoV. The
I2C address can be changed using the vl53lmz_set_i2c_address() function. To use the SPI, the multisensor is
wired using an independent slave configuration (the NCS pin).
In order to change the device I2C address without affecting others on the I2C bus, it is important to disable the
I2C communication of the devices not being changed. The procedure is as follows:
1. Power up the system as normal.
2. Pull down the LPn pin of the device that will not have its address changed.
3. Pull up the LPn pin of the device that has the I2C address changed.
4. Program the I2C address to the device using function vl53lmz_set_i2c_address() function.
5. Pull up the LPn pin of the device not being reprogrammed.
All devices should now be available on the I2C bus. Repeat the above steps for all the devices in the system that
require a new I2C address.
Figure 4. Multiple sensors on I2C bus
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Schematics and I2C/SPI configuration
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Figure 5. Multiple sensors on SPI
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