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theory:sensor_technology:st23_bus_interfaces [2018/10/10 02:18]
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-====== Bus Interfaces ====== 
- 
-//Sensors have to be at specific locations to pick up the required physical quantity correctly. As a result, a sensor system may result into many, long wires to the sensors or sensor modules. While many sensors are still connected by analog wires (either with or without a pre-amplifier),​ the overall trend is to move to digital, standardised bus systems. // 
- 
-===== The advantages of bus interfaces and networks ===== 
- 
-The reasons to use a bus or bus system are: 
-  * Reduce the number of wires and simplify the wiring plan by using star-based or chain networks 
-  * Reduce the influence of electronic noise by going digital 
-  * Implementig channel coding 
-  * Adding metadata for error management 
-  * Adding metadata for realtime systems 
-  * Adding metadata for safety and security purposes 
-  * Standardization of physical and electrical interfaces for cost reduction and easy serviceability 
- 
-There are three examples where digital buses were introduced after electronic systems evolved for decades: 
- 
-==== I2C, SPI and electronic appliances ====  
- 
-In the 1970'​s,​ TV sets had become complex and in the mean time, digital controllers were introduced. The wiring architectures had become very sophisticated and there became clear different wires for control- and setting data opposite to data channels for (digital) video information. Therefore, Philips introduced in 1979 the //Inter IC Bus//, short I<​sup>​2</​sup>​C bus. This is a serial, synchronous bus which was originally intended for rates up to $100 kb/s$ over a maximum range of $1m$. This has changed the architecture of TV sets, and also other equipment, dramatically. Sub-modules within a TV architecture got their own status, linked only by the  I<​sup>​2</​sup>​C bus, and remote units, like the control panel, were easier to wire.\\ 
-Although the I<​sup>​2</​sup>​C bus is not intended for sensors, it is used for sensor chips. An alternative,​ which is similar in the sense that it comprises a clock-line and a serial data line, is the //Serial Peripheral Interface// (SPI) as introduced by Motorola in the late 1980'​s. Also this bus protocol is implemented in many sensor chips. 
- 
-==== CAN bus in car industry ==== 
- 
-Similar to what happened in the architecture of appliances due to I<​sup>​2</​sup>​C,​ the automotive industry experienced a shift towards digital buses in the late 1980'​s. The //​Controller Area Network bus// (CAN bus) is a vehicle bus standard developed at Robert Bosch GmbH. It has changed the car's architecture of the control system into central microcontrollers,​ communicating to remote units over a serial bus.\\ 
-Later on, more dedicated buses for safety critical subsystems were developed like //FlexRay// and the //AUTOSAR (AUTomotive Open System ARchitecture)//​ has formalized the software architecture. The CAN bus is also used as industrial fieldbus in general automation environments,​ primarily due to the low cost of some CAN controllers and processors. 
-==== Industrial Ethernet ==== 
- 
-In industrial machines for manufacturing,​ logistics (conveyer belts) and packaging, we see the integration of business and technical processes. Manufacturers want to control and monitor their production in a central place. As a result, we see the introduction of IT technologies and methods on the manufacturing floor. To be more specific, the technical consequences are: 
-  * Standard Operating Systems on PC automation systems (like Windows, Windows Embedded, Linux and Linux Embedded) 
-  * Use of Ethernet 
-  * Standard internet protocols like http (remote control, etc.)  
-  * Technologies like OPC, XML or TCP/IP 
-Current sensor modules for industry, are available with one of the Ethernet based industry buses. 
- 
-===== Buses optimised for sensor networks ===== 
- 
-The most common protocols to implement communication from sensors to the main controller in electronic microsystems are I<​sup>​2</​sup>​C and SPI. A good overview is given in the paper by Zhou((Zhou, J., & Mason, A. (2002), Communication buses and protocols for sensor networks, Sensors, 2(7), 244-257, www.mdpi.com/​1424-8220/​2/​7/​244/​pdf)). Also the webpage of Byte Paradigm((Byte Paradigm - Introduction to I<​sup>​2</​sup>​C and SPI protocols, http://​www.byteparadigm.com/​applications/​introduction-to-i2c-and-spi-protocols/​)) gives a good comparison of I<​sup>​2</​sup>​C and SPI. 
- 
-===== Industrial buses ===== 
- 
-In fact, an industrial machine is normally a distributed computer. This means there is a central controller (either PLC or Industrial PC as a master) which is connected to distant slave couplers by means of a //field bus//​((http://​measure.feld.cvut.cz/​en/​system/​files/​files/​en/​education/​courses/​AE3B38PRT/​Sensor_buses_and_DAQ_software.pdf)),​ ((http://​people.cs.pitt.edu/​~mhanna/​Master/​Introduction.pdf)). From the coupler //slices// may address sensors and actuators by means of low-end field buses in a slave-slave or master-slave relation. 
- 
-The current topics of interest are: 
-  * Shift towards Ethernet based protocols (PROFINET, EtherCAT, EtherNet/​IP) 
-  * Integration of ICT services on the same bus 
-  * Ring redundancy 
-  * Power over Ethernet 
-  * Real-time features (because they are part of a distributed computer) 
-  * Integrated cyber security systems (detect autenticity) 
-  * Integrated safety systems (guaranteed and predictable stop conditions) 
-  * Extension to lower-end interconnect like point-to-point IO-Link 
- 
-Recommended reading about EtherNet based buses is: 
-  * Industrial EtherNet Facts, System comparison - the 5 major technologies((Industrial EtherNet Facts, System comparison - the 5 major technologies,​ EtherNet Powerlink Standardization Group, http://​www.ethernet-powerlink.org/​en/​downloads/​industrial-ethernet-facts/​)) 
-  * EtherCAT Communication((EtherCAT Communication,​ Communication Principles, EtherCAT Technology Group, https://​www.ethercat.org/​en/​downloads/​downloads_4A8B20A0EDC348888CC85417677A359F.htm)) and Industrial Ethernet Technologies((Industrial Ethernet Technologies,​ EtherCAT Technology Group, https://​www.ethercat.org/​download/​documents/​Industrial_Ethernet_Technologies.pdf)) by the EtherCAT Technology Group 
-===== Buses from car industry ===== 
- 
-  * CAN 
-  * FlexRay 
-====== Sensor Technology TOC ====== 
- 
-These are the chapters for the Sensor Technology course: 
-  * Chapter 1: [[theory:​sensor_technology:​st1_measurement_theory|Measurement Theory]] 
-  * Chapter 2: [[theory:​sensor_technology:​st2_measurement_errors|Measurement Errors]] 
-  * Chapter 3: [[theory:​sensor_technology:​st3_measurement_technology|Measurement Technology]] 
-  * Chapter 4: [[theory:​sensor_technology:​stb_conventions_for_good_graphs_and_tables|Circuits,​ Graphs, Tables, Pictures and Code]] 
-  * Chapter 5: [[theory:​sensor_technology:​st4_sensor_theory|Basic Sensor Theory]] 
-  * Chapter 6: [[theory:​sensor_technology:​st6_sensoractuatorsystems|Sensor-Actuator Systems]] ​ 
-  * Chapter 7: [[theory:​sensor_technology:​st7_modelling_main|Modelling]] 
-  * Chapter 8: [[theory:​sensor_technology:​st8_accelerometer_model|Modelling:​ The Accelerometer]] - example of a second order system 
-  * Chapter 9: [[theory:​sensor_technology:​st9_scaling|Modelling:​ Scaling]] - why small things appear to be stiffer 
-  * Chapter 10: [[theory:​sensor_technology:​st10_lumped_element_models|Modelling:​ Lumped Element Models]] 
-  * Chapter 11: [[theory:​sensor_technology:​st11_finite_element_models|Modelling:​ Finite Element Models]] 
-  * Chapter 12: [[theory:​sensor_technology:​st12_impedance_spectroscopy|Modelling:​ Transducer Characterization by Impedance Spectroscopy]] 
-  * Chapter 13: [[theory:​sensor_technology:​st13_lumped_element_models_advanced|Modelling:​ Systems Theory]] 
-  * Chapter 14: [[theory:​sensor_technology:​st14_differential_equation_numerical_models|Modelling:​ Numerical Integration]] 
-  * Chapter 15: [[theory:​sensor_technology:​st15_signal_conditioning_and_sensor_read-out|Signal Conditioning and Sensor Read-out]] 
-  * Chapter 16: [[theory:​sensor_technology:​st16_resistive_sensors|Resistive Sensors]] 
-  * Chapter 17: [[theory:​sensor_technology:​st17_capacitive_sensors|Capacitive Sensors]] 
-  * Chapter 18: [[theory:​sensor_technology:​st18_magnetic_sensors|Magnetic Sensors]] 
-  * Chapter 19: [[theory:​sensor_technology:​st19_optical_sensors|Optical Sensors]] 
-  * Chapter 20: [[theory:​sensor_technology:​st20_actuators|Actuators]] - an example of an electrodynamic motor 
-  * Chapter 21: [[theory:​sensor_technology:​st21_actuator_models|Actuator principles for small speakers]] 
-  * Chapter 22: [[theory:​sensor_technology:​st22_adc_and_dac|ADC and DAC]] 
-  * Chapter 23: Bus Interfaces - SPI, I<​sup>​2</​sup>​C,​ IO-Link, Ethernet based 
-  * Appendix A: [[theory:​sensor_technology:​sta_easyunitconversion|Systematic unit conversion]] <- Next 
-  * Appendix B: [[theory:​sensor_technology:​stc_common_mode_rejection_ratio_cmrr|Common Mode Rejection Ratio (CMRR)]] 
-  * Appendix C: [[theory:​sensor_technology:​std_schmitt_trigger|A Schmitt Trigger for sensor level detection]] 
- 
  
theory/sensor_technology/st23_bus_interfaces.1539137908.txt.gz · Last modified: 2018/10/10 02:18 by 54.36.148.192