acconeer A121 I2C Distance Detector User Guide

acconeer A121 I2C Distance Detector

Product Information

• Specifications:
  • Product: I2C Distance Detector
  • Manufacturer: Acconeer AB
  • Version: a121-v1.3.0
  • Release Date: October 6, 2023

The I2C Distance Detector is a device designed to measure distances using the I2C communication protocol. It provides accurate distance measurements and can be used for various applications.

Product Usage Instructions

• Read Detector Status:
  • To read the detector status, follow the instructions provided in the user manual.
• Writing a Command:
  • To send commands to the detector, use the specified protocol for writing commands as outlined in the user guide.
• Setup and Measure:
  • Follow the setup instructions to configure the detector and initiate distance measurement.
• Advanced Usage:
  • Apply Configuration and Calibration Separately:
  • For advanced users, it is possible to apply configuration settings and calibration separately for precise measurements.
  • Re-calibration:
  • If needed, the detector can be recalibrated following the provided guidelines in the user manual.
  • Measure on Wake Up Mode:
  • In wake-up mode, the detector can perform measurements upon activation. Refer to the manual for detailed instructions.
  • Debug UART Logs:
  • View debug logs via the UART interface for troubleshooting and analysis purposes.
  • Reset Module:
  • To reset the module, use the recommended procedure to ensure proper functionality.

FAQ:

• Q: How often should the detector be recalibrated?
  • A: The detector should be recalibrated periodically as per the usage and environmental conditions. It is recommended to recalibrate if inconsistencies are observed in measurements.
• Q: Can the detector measure distances in varying lighting conditions?
  • A: The detector’s performance may vary in different lighting conditions. For optimal results, use the detector in controlled lighting environments.

Documentation Overview

Acconeer SDK Documentation Overview

To better understand what SDK document to use, a summary of the documents is shown in the table below.

Table 1: SDK document overview.

RSS API documentation (HTML)
RSS-API| The complete C API documentation.| –  RSS application implementation

–  Understanding RSS API functions

User guides (PDF)
A121 Assembly Test| Describes the Acconeer assembly

test functionality.

| –  Bring-up of HW/SW

–  Production test implementation

A121 Breathing

Reference Application

| Describes the functionality of the

Breathing Reference Application.

| – Working with the Breathing

Reference Application

A121 Distance Detector| Describes usage and algorithms

of the Distance Detector.

| – Working with the Distance Detector

A121 SW Integration

| Describes how to implement each integration function needed to use the Acconeer sensor.| – SW implementation of custom HW integration
A121 Presence Detector| Describes usage and algorithms of the Presence Detector.| – Working with the Presence Detector
A121 Smart Presence

Reference Application

| Describes the functionality of the Smart Presence Reference Application.| – Working with the Smart Presence Reference Application
A121 Sparse IQ Service| Describes usage of the Sparse IQ Service.| – Working with the Sparse IQ Service
A121 Tank Level

Reference Application

| Describes the functionality of the Tank Level Reference Application.| – Working with the Tank Level Reference Application
A121 STM32CubeIDE| Describes the flow of taking an Acconeer SDK and integrating it into STM32CubeIDE.| – Using STM32CubeIDE
A121 Raspberry Pi Software| Describes how to develop for Raspberry Pi.| – Working with Raspberry Pi
A121 Ripple| Describes how to develop for Ripple.| – Working with Ripple on Raspberry Pi
XM125 Software| Describes how to develop for XM125.| – Working with XM125
I2C Distance Detector| Describes the functionality of the I2C Distance Detector Application.| – Working with the I2C Distance Detector Application
I2C Presence Detector| Describes the functionality of the I2C Presence Detector Application.| – Working with the I2C Presence Detector Application
Handbook (PDF)

Handbook

| Describes different aspects of the Acconeer offers, for example, radar principles and how to configure| –  To understand the Acconeer sensor

–  Use case evaluation

Readme (txt)
[README| Various target-specific information and links| – After SDK download

Detector Application

I2C Distance Detector Application

• The I2C Distance Detector is an application that implements the Acconeer Distance Detector with a register-based I2C interface.
• The functionality of the distance detector is described in A121 Distance Detector User Guide.pdf or Acconeer Docs.
• Note: Some of the registers like start and end have a different unit in the I2C Distance Detector, millimetres instead of meters, to make it easier to handle the register values as integers.

Usage

• The module must be ready before the host starts I2C communication.
• The module will enter a ready state by following this procedure.
• Set the wake-up pin of the module HIGH.
• Wait for the module to be ready, this is indicated by the MCU INT pin being HIGH.
• Start I2C communication.
• The module will enter a low-power state by following this procedure.
• Wait for the module to be ready, this is indicated by the MCU INT pin being HIGH.
• Set the UP pin of the module LOW.
• Wait for the ready signal, the MCU INT pin, to become LOW.

Read Detector Status

• The status of the module can be acquired by reading the Detector Status register, The most important bits are the Busy and Error bits.
• The Busy bit must not be set when a new command is written. If any of the Error bits are set the module will not accept any commands except the RESET MODULE command.

Writing a command

• A command is written to the Command register. When a command is written the Busy bit in the Detector Status register is set and it will be cleared automatically when the command has finished.

Setup and Measure

• Before the module can perform distance measurements it must be configured and calibrated. The following steps is an example of how this can be achieved.
• Note: The configuration parameters can not be changed after a APPLY CONFIG AND CALIBRATE or a APPLY CONFIGURATION command. If reconfiguration is needed the module must be restarted by writing

RESET MODULE to the Command register.

• Power on module
• Read the Detector Status register and verify that neither Busy nor Error bits are set.
• Write configuration to configuration registers, for example, the Start register and the End register.
• Write APPLY CONFIG AND CALIBRATE to the Command register.
• Poll Detector Status until Busy bit is cleared.
• Verify that no Error bits are set in the Detector Status register.
• Write MEASURE DISTANCE to the Command register.
• Poll Detector Status until Busy bit is cleared.
• Verify that no Error bits are set in the Detector Status register.
• Read the Detector Result register
  • If MEASURE DISTANCE ERROR is set the measurement failed.
  • If CALIBRATION NEEDED is set the sensor needs to be re-calibrated with the RECALIBRATE command.
  • The number of peak distances detected can be read in the NUM DISTANCES field.
• Read PeakX Distance and PeakX Strength registers depending on how many distances were detected.
• The module is ready for a new MEASURE DISTANCE command.

Advanced Usage

• Apply Configuration and Calibration separately
  • Some use-cases require control over when the system is calibrated, therefore the Apply Configuration and Calibrate can be performed as individual steps.
  • Power on module
  • Read the Detector Status register and verify that neither Busy nor Error bits are set.
  • Write configuration to configuration registers, for example, the Start register and End register.
  • Write APPLY CONFIGURATION to the Command register
  • Poll Detector Status until Busy bit is cleared.
  • Verify that no Error bits are set in the Detector Status register.
  • Write CALIBRATE to Command Register
  • Poll Detector Status until Busy bit is cleared.
  • Verify that no Error bits are set in the Detector Status register.
  • The module is ready for a MEASURE DISTANCE command.
• Re-calibration
  • Re-calibration must be done as soon as the CALIBRATION NEEDED bit is set in the Detector Result register.
  • Re-calibration is performed by writing RECALIBRATE to the Command register.
• Measure on Wake Up Mode
  • Measure on Wake Up mode can be enabled by writing a non-zero value to the Measure On Wakeup register. When
  • Measure on Wake Up is enabled, the module will perform a distance measurement every time it is woken by the
  • WAKE UP pin. The measurement will be ready when the MCU INT pin becomes HIGH.
• Debug UART logs
  • UART logging can be enabled on the DEBUG UART by writing ENABLE UART LOGS to the Command register.
  • The detector configuration can be logged on the UART by writing LOG CONFIGURATION to the Command register.
  • UART logging can be disabled by writing DISABLE UART LOGS to the Command register.
• Reset Module
  • The module can be restarted by writing RESET MODULE to the Command register.
  • After the restart, the detector must be configured again.

Register Protocol

I2C Slave Address

• The default slave address is 0x52.

Protocol Byte Order

• Both register address, 16-bit, and register data, 32-bit, are sent in big-endian byte order.

I2C Write Register(s)

• A write register operation consists of an I2C write of two address bytes and four data bytes for each register to write.
• Several registers can be written in the same I2C transaction, the register address will be incremented by one for each four data bytes.
• Example 1: Writing six bytes will write one register, two address bytes and four data bytes.
• Example 2: Writing 18 bytes will write four registers, two address bytes and 16 data bytes.

For example operation, write 0x11223344 to address 0x0025.

Example Waveform: Write register with address 0x0100, the data sent from the master to the slave is 0x00000001
I2C Read Register(s)

• A read register operation consists of an I2C write of two address bytes followed by an I2C read of four data bytes for each register to read. Several registers can be read in the same I2C transaction, the register address will be incremented by one for each four data bytes.
• Example 1: Writing two bytes and reading four bytes will read one register.
• Example 2: Writing two bytes and reading 16 bytes will read four registers.

Example operation, read 0x12345678 from address 0x0003.

Example Waveform: Read register with address 0, the data sent from the slave to the master is 0x00010001

Register Protocol – Low Power Mode I2C Communication with Low Power Mode

Low power example

Low Power Example: Wake up, Setup Distance Detector, Power down, Wait 1s, Wake up, Measure distance, Power down

Low Power Example: Magnification of Wake up, Setup Distance Detector, Power down

Low Power Example: Magnification of Wake up, Measure distance, Power down

Low power example with ’Measure on wake up’

Measure on Wake Up Example: Magnification of Wake up, Measure on wake up, Power down

File Structure

The I2C Distance Detector application consists of the following files.

• acc reg protocol.c A generic protocol handler implementation.
• distance reg protocol.c The specific register protocol setup for the I2C Distance Detector.
• distance reg protocol access.c The register read and write access functions for the I2C Distance Detector.
• i2c application system stm32.c System functions, such as I2C handling, GPIO control and low power state
• i2c distance detector.c The I2C Distance Detector application.

Embedded Host Example

This is an example implementation of the host read and write register functions using the STM32 SDK.

Register Read/Write functions

Detector setup functions

Registers

Register Map

Register Descriptions Version

• MAJOR – Major version number
• MINOR – Minor version number
• PATCH – Patch version number

Protocol Status

• PROTOCOL STATE ERROR – Protocol state error
• PACKET LENGTH ERROR – Packet length error
• ADDRESS ERROR – Register address error
• WRITE FAILED – Write register failed
• WRITE TO READ ONLY – Write to read only register

Measure Counter

performed since restart.

Detector Status

• RSS REGISTER OK – RSS register OK
• CONFIG CREATE OK – Configuration create OK
• SENSOR CREATE OK – Sensor create OK
• DETECTOR CREATE OK – Detector create OK
• DETECTOR BUFFER OK – Detector get buffer size OK
• SENSOR BUFFER OK – Memory allocation of sensor buffer OK
• CALIBRATION BUFFER OK – Memory allocation of calibration buffer OK
• CONFIG APPLY OK – Detector configuration apply OK
• SENSOR CALIBRATE OK – Sensor calibrate OK
• DETECTOR CALIBRATE OK – Detector calibrate OK
• RSS REGISTER ERROR – RSS register error
• CONFIG CREATE ERROR – Configuration creates an error
• SENSOR CREATE ERROR – The sensor creates an error
• DETECTOR CREATE ERROR – The detector creates an error
• DETECTOR BUFFER ERROR – Detector get buffer size error
• SENSOR BUFFER ERROR – Memory allocation of sensor buffer error
• CALIBRATION BUFFER ERROR – Memory allocation of calibration buffer error
• CONFIG APPLY ERROR – Detector configuration applies error
• SENSOR CALIBRATE ERROR – Sensor calibrate error
• DETECTOR CALIBRATE ERROR – Detector calibrate error
• DETECTOR ERROR – Detector error occurred, restart necessary
• BUSY – Detector busy

Distance Result

• NUM DISTANCES – The number of detected distances
• NEAR START EDGE – Indicating that there might be an object near the start point of the measured range
• CALIBRATION NEEDED – Indication of sensor calibration needed. The sensor calibration needs to be redone
• MEASURE DISTANCE ERROR – The measure command failed
• TEMPERATURE – Temperature in sensor during measurement (in degrees Celsius). Note that it has poor absolute accuracy and should only be used for relative temperature measurements.

Peak0 Distance

Note: This value is a factor of 1000 larger than the RSS value.

Peak1 Distance

Note: This value is a factor 1000 larger than the RSS value.

Peak2 Distance

Note: This value is a factor 1000 larger than the RSS value.

Peak3 Distance

Note: This value is a factor 1000 larger than the RSS value.

Peak4 Distance

Note: This value is a factor 1000 larger than the RSS value.

Peak5 Distance

Note: This value is a factor of 1000 larger than the RSS value.

Peak6 Distance

Note: This value is a factor of 1000 larger than the RSS value.

Peak7 Distance

Note: This value is a factor of 1000 larger than the RSS value.

Peak8 Distance

Note: This value is a factor of 1000 larger than the RSS value.

Peak9 Distance

Note: This value is a factor 1000 larger than the RSS value.

Peak0 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak1 Strength

Note: This value is a factor 1000 larger than the RSS value.

Peak2 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak3 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak4 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak5 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak6 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak7 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak8 Strength

Note: This value is a factor of 1000 larger than the RSS value.

Peak9 Strength

factor of 1000 larger than the RSS value.

Start

Note: This value is a factor of 1000 larger than the RSS value.
Default Value| 250

End

Note: This value is a factor of 1000 larger than the RSS value.
Default Value| 3000

Max Step Length

length is calculated based on

profile.

Default Value| 0

Close-Range Leakage Cancellation

Signal Quality

higher HWAAS) and higher power consumption.
Note: This value is a factor of 1000 larger than the RSS value.
Default Value| 15000

Max Profile

• PROFILE1 – Profile 1
• PROFILE2 – Profile 2
• PROFILE3 – Profile 3
• PROFILE4 – Profile 4
• PROFILE5 – Profile 5

Threshold Method

• FIXED AMPLITUDE – Fixed amplitude threshold
• RECORDED – Recorded threshold
• CFAR – CFAR threshold
• FIXED STRENGTH – Fixed strength threshold

Peak Sorting

• CLOSEST – Sort peaks by range, closest first
• STRONGEST – Sort peaks by amplitude, strongest first

Num Frames Recorded Threshold

Fixed Amplitude Threshold Value

factor 1000 larger than the RSS value.
Default Value| 100000

Threshold Sensitivity

Note: This value is a factor of 1000 larger than the RSS value.
Default Value| 500

Reflector Shape

• GENERIC – Generic reflector shape
• PLANAR – Planar reflector shape

Fixed Strength Threshold Value

Note: This value is a factor of 1000 larger than the RSS value.
Default Value| 0

Measure On Wakeup

Command

• APPLY CONFIG AND CALIBRATE – Apply configuration, calibrate sensor and detector
• MEASURE DISTANCE – Measure the distance
• APPLY CONFIGURATION – Apply the configuration
• CALIBRATE – Calibrate sensor and detector
• RECALIBRATE – Re-calibrate sensor and detector
• ENABLE UART LOGS – DEBUG: Enable UART Logs
• DISABLE UART LOGS – DEBUG: Disable UART Logs
• LOG CONFIGURATION – DEBUG: Print detector configuration to UART
• RESET MODULE – Reset module, needed to make a new configuration

Disclaimer

• The information herein is believed to be correct as of the date issued. Acconeer AB (“Acconeer”) will not be responsible for damages of any nature resulting from the use or reliance upon the information contained herein.
• Acconeer makes no warranties, expressed or implied, of merchantability or fitness for a particular purpose or course of performance or usage of trade.
• Therefore, it is the user’s responsibility to thoroughly test the product in their particular application to determine its performance, efficacy and safety. Users should obtain the latest relevant information before placing orders.
• Unless Acconeer has explicitly designated an individual Acconeer product as meeting the requirement of a particular industry standard, Acconeer is not responsible for any failure to meet such industry standard requirements.
• Unless explicitly stated herein in this document Acconeer has not performed any regulatory conformity test. It is the user’s responsibility to ensure that necessary regulatory conditions are met and approvals have been obtained when using the product.
• Regardless of whether the product has passed any conformity test, this document does not constitute any regulatory approval of the user’s product or application using Acconeer’s product.
• Nothing contained herein is to be considered as permission or a recommendation to infringe any patent or any other intellectual property right. No license, express or implied, to any intellectual property right is granted by Acconeer herein.
• Acconeer reserves the right to at any time correct, change, amend, enhance, modify, and improve this document and/or Acconeer products without notice.
• This document supersedes and replaces all information supplied before the publication hereof.

© 2023 by Acconeer AB – All rights reserved

References

• Distance Detection — Acconeer docs

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