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KNX is the only bus system worldwide that offers the complete range of transmission media for building control systems: Twisted Pair, Powerline, Radio Frequnecy and Ethernet IP. Transmission media can easily be coupled with KNX media couplers. The KNX applications are commissioned with ETS, the manufacturer, product and trade independent tool.

 

From the Idea to the Finished Product, the list of questions for a KNX novice on how to implement KNX into a new device can be quite long:

• Which KNX media (e.g. Twisted Pair or Radio Frequency) should be used?
• Which software requirements does KNX demand?
• Which communication objects – data formats – should be used and how are they programmed?
• What are the hardware requirements for the device?
• Are there standard components?
• How will the device be commissioned, i.e., which configuration modes should be supported?
• Is there technical support that can assist during the development?
• How is the certification process?

 

It is helpful to learn about the available KNX standard components which are available on the market for the different media to get a better idea of which solution may  be suited to develop a certain device.

 

 

For more information about available KNX devices please contact:

 

 

Eelectron	Opternus Components GmbH	Tapko Technologies GmbH	Weinzierl Engineering GmbH
www.eelectron.com	www.opternus.com	www.tapko.de	www.weinzierl.de

 

 

Implementation Aspects of KNX TP Device

 

There are several technical terms which are common on the market like „BCU“, „BIM“, „SIM“, „TPUART“, „chipset“ and „communication stack“. These terms represent the different possibilities on how to develop a KNX TP device.

 

BCU „Bus coupling units“

These are system devices which include the KNX coupling circuitry, a microprocessor and are delivered with housing. The device developer only needs to develop the application module, the application hardware and software.

 

BIM „Bus Interface Modules“ 

They are basically built up like the inside of a BCU with additional I/O ports. BIMs are sold as modules which can be soldered directly to the circuit board.

There are versions available with 8kbyte and 48 kbyte flash memory for the application software. The software development takes place with a development environment consisting of „Evaluationboard“, „On-Chip Debug Emulator“ and C-Compiler.

 

SIM „Serial Interface Modules“

They contain the complete communication system with applications. The application hardware and software is coupled with the communication part via serial interface. SIMs are sold as modules which are soldered directly to the circuit board.

 

Chipset

Chipsets of BIMs are offered to circumvent the mechanical constraints of BIMs. There is no difference between BIMs and chipsets with regard to the software.

 

TPUART

The TPUART only contains the coupling to KNX. The communication software is supplied by a micro-controller. The TPUART was developed to relieve the micro controller of the bit coding and decoding duty on the one hand and to allow the coupling to KNX through different micro-controllers on the other hand.

 

Communication Stack

To develop a KNX device with the TPUART, a communication stack is required. This kinds of coupling is the most effective, flexible and low-cost way of developing a KNX device. To eliminate the need for the developer to familiarize themselves with details of the KNX communication, KNX system vendors offer the KNX communication stack. The coupling to KNX is performed through external KNX coupler like TPUART, FZE1066. The KNX communication stack offers additional interfaces to program the actual application.

 

What is the right solution?

Small number of production units: The BIM is recommended as it will offer low development and certification costs. If there is little space or the number of production units increase, it is recommended to integrate the chipset into the existing electronic circuit. The initial costs are just a little higher as compared to BIM. The TPUART is the best solution, but with the biggest development- and certification effort. It is only cost-efficiency for products with a high sales volume.

 

 

Implementation Aspects for KNX PL units

 

Standardized BCUs and modules (PIM) are also available for KNX PL (110) similar to Twisted Pair.

 

BCU „Bus coupling units“

These are system devices which include the KNX coupling circuitry, a microprocessor and are delivered with housing. The device developer only needs to develop the application module, the application hardware and software.

 

PIM „Powerline Interface Modules“ 

They are basically built up of the low voltage part of the BCU. PIMs are modules that are soldered to the circuit board together with other network coupling parts.

 

ACIS with Communication Stack

An ASIC for PL110 is responsible for sending and receiving bits. To build a KNX device based on such an ASIC a KNX stack for Powerline (communication software) is necessary. A communication stack contains interfaces for the programming of the application.

 

What is the right solution?

BCUs are best suited for small production numbers to develop cost effective devices. For the medium sized product, PIMs are recommended - a circuit diagram is available. The development of PL devices with ASIC and communication stack requires larger investments as compared to BCUs and PIMs and is therefore usually suited for manu-facturers with high production numbers.

 

 

Implementation Aspects for KNX RF

 

The development of KNX RF devices does not require special KNX parts. A KNX RF node basically consists of the following elements:

 

Transceiver Chip

For KNX RF no dedicated chip is necessary.

Today there are a couple of chips available which can be used to implement a KNX RF node. For unidirectional devices, low cost transmit-only chips are available.

 

RF circuit

The transceiver builds togethere with a couple of passive components the RF circuit. Based on the reference design of the chip manufacturer, a circuit can be designed and optimized to the KNX RF requirements.

 

Microcontroller

The core of any KNX device is a microcontroller which handles the communication as well as the application task. For RF one of the most important requirements is low power consumption. The interface logic to connect the transceiver should be present in most of today’s controllers.

 

Communication stack

The KNX standard defines a complex protocol which leads to a high implementation and certification effort. The communication stack is the system software for a KNX RF device. It controls the transceiver and handles complete communication, including the configuration procedure. The communication stack provides an interface (API) for application development.