Docklight Application Note: RS422/485 communication
Contents
1. Docklight_Application_Note_RS422_485 doc Date 2015 10 27 Docklight Application Note RS422 485 communication Applies to Docklight V2 1 Docklight Scripting V2 1 Auth Flachmann He V1 4 Minor rev 2015 10 27 He V1 3 Minor Corr 2014 10 14 He V1 2 Figure 1 2 corr 2014 04 19 Fl V1 1 Minor correct 2008 09 19 He Flachmann und Heggelbacher www fuh edv de Docklight Application Note Page V1 0 First release 2007 08 13 Fl 1 5 Ver Comment Date Name Docklight Application Note RS422 485 communication Docklight can access any COM communication port available in Windows Physically these ports will be RS232 SUB D9 interfaces in many cases However it is also possible to use Docklight for other communication standards such as RS485 and RS422 which have a different electrical design to RS232 but follow the RS232 communication mechanism Unlike RS232 a RS422 485 communication link allows bus topologies that connect e g one master with several slave devices The following sections describe additional settings and options available in Docklight that facilitate analyzing and debugging such data links TIP For high speed and time critical RS485 and RS422 bus monitoring see also our Docklight Tap 485 hardware accessory and the related Application Note Docklight Tap Pro and Docklight Tap 485 3 http docklight de pdf Docklight_Application_Note_TapPro_Tap485 pdf 1 Communicating over a 2 wire RS485 l2. ink Data B Data A GND RD B RD A GND DATA B DATA A GND USB to RS422 485 Serial Converter RS 485 Master Device 1 Docklight PC 2 Wire RS 485 connection Figure 1 Communicating over a 2 wire RS485 link For communicating over a two wire RS485 bus a RS422 485 interface is required on the Docklight PC e g a USB to RS485 422 adapter as listed in section 5 RS422 RS485 Reference Hardware Use the following setup Open the Project Settings dialog and choose Send Receive Mode At Send Receive on comm channel select the COM port assigned to your RS422 RS485 interface Docklight_Application_Note_RS422_485 doc Date 2015 10 27 Docklight Application Note RS422 485 communication Applies to Docklight V2 1 Docklight Scripting V2 1 Auth Flachmann He V1 4 Minor rev 2015 10 27 He V1 3 Minor Corr 2014 10 14 He V1 2 Figure 1 2 corr 2014 04 19 Fl V1 1 Minor correct 2008 09 19 He Flachmann und Heggelbacher www fuh edv de Docklight Application Note Page V1 0 First release 2007 08 13 Fl 2 5 Ver Comment Date Name Figure 2 Docklight Project Settings for 2 wire RS485 communication 2 Monitoring a 2 wire link RS485 half duplex Use the same settings as in the previous section 1 Communicating over a 2 wire RS485 link When monitoring a two wire bus Docklight cannot distinguish between two different data d
3. irections and use two different colors blue red to distinguish between master and slave device telegrams You will only see one data direction red inside the communication window But Docklight provides a number of functions to process such data streams and separate the master and slave telegrams 1 In most applications there is a significant pause time between the master requests and the slave answers In this case use the menu Tools gt Options gt Date Time Stamps then activating Pause detection and choosing a time small enough to safely detect this silence between the master and slave telegrams 0 1 seconds can be a good default value to start with 2 If there is no significant pause between the master telegrams and the slave responses you need to teach Docklight something about your data stream and the application protocol used Using so called Receive Sequence definitions see http docklight de manual receivesequence htm you can make Docklight trigger on certain data that defines the telegram end For example if your protocol uses an ETX ASCII code 03 character to mark the telegram end you could define a Receive Sequence that triggers on this character and inserts an additional line break time stamp after receiving such a character Docklight_Application_Note_RS422_485 doc Date 2015 10 27 Docklight Application Note RS422 485 communication Applies to Docklight V2 1 Docklight Scripting V2 1 Auth Flach
4. mann He V1 4 Minor rev 2015 10 27 He V1 3 Minor Corr 2014 10 14 He V1 2 Figure 1 2 corr 2014 04 19 Fl V1 1 Minor correct 2008 09 19 He Flachmann und Heggelbacher www fuh edv de Docklight Application Note Page V1 0 First release 2007 08 13 Fl 3 5 Ver Comment Date Name 3 Monitoring a 4 wire link RS422 or RS485 full duplex TD B TD A RD B RD A GND TD B TD A RD B RD A GND TD B TD A RD B RD A GND TD B TD A RD B RD A GND USB to RS422 485 Serial Converter RS 485 Master Device 1 Docklight PC 4 Wire RS 485 connection Figure 3 Monitoring a 4 wire RS422 485 link Monitoring a 4 wire RS422 RS485 network is similar to RS232 monitoring applications see http docklight de manual monitortheserialcommunicationb htm Two free RS422 485 interfaces resp two COM ports are required for monitoring and Docklight can distinguish between two data directions e g master telegrams blue and slave responses red Use the following setup Open the Project Settings dialog and choose Monitoring Mode At Receive Channel 1 and Receive Channel 2 choose the two COM ports assigned to the RS422 RS485 interfaces Docklight_Application_Note_RS422_485 doc Date 2015 10 27 Docklight Application Note RS422 485 communication Applies to Docklight V2 1 Docklight Scripting V2 1 Au
5. th Flachmann He V1 4 Minor rev 2015 10 27 He V1 3 Minor Corr 2014 10 14 He V1 2 Figure 1 2 corr 2014 04 19 Fl V1 1 Minor correct 2008 09 19 He Flachmann und Heggelbacher www fuh edv de Docklight Application Note Page V1 0 First release 2007 08 13 Fl 4 5 Ver Comment Date Name Figure 4 Docklight Project Settings for 4 wire RS422 monitoring 4 RS422 485 Specific Project Settings in Docklight RS485 Transceiver Control menu Project Settings tab Flow Control Some RS232 to RS485 or USB to RS485 converters require manual RTS control I e the DTE your PC needs to tell the converter when it should enable its RS485 driver for transmission This is usually done using the RTS status line of the COM port If you choose RS485 Transceiver Control in Docklight the serial port driver sets RTS High before transmitting the first character and RTS Low after the last character has been transmitted Please refer to the operating manual of your RS485 interface converter and check if the RS485 Transceiver Control setting is required or not Most RS485 products offer an automatic mode where the RTS signal is not required and Flow Control Support Off default setting can be used in Docklight Figure 5 Flow Control Setting for RS485 Transceiver Control Docklight_Application_Note_RS422_485 doc Date 2015 10 27 Docklight Application Note RS422 485 communication Applies
6. to Docklight V2 1 Docklight Scripting V2 1 Auth Flachmann He V1 4 Minor rev 2015 10 27 He V1 3 Minor Corr 2014 10 14 He V1 2 Figure 1 2 corr 2014 04 19 Fl V1 1 Minor correct 2008 09 19 He Flachmann und Heggelbacher www fuh edv de Docklight Application Note Page V1 0 First release 2007 08 13 Fl 5 5 Ver Comment Date Name 5 RS422 RS485 Reference Hardware MOXA TCC 100 100I www moxa com Isolated RS232 to RS 422 485 converter MOXA UPort 1150 UPort 1150I www moxa com 1 port RS 232 422 485 USB to serial converters USB Edgeport 2i www digi com 2 RS 422 485 serial DB 9 interfaces VScom USB COM PRO www vscom de 1 Port RS232 422 485 software configurable 6 References 1 Docklight Scripting V2 1 User Manual from edition 08 2015 http docklight de pdf docklight_scripting_manual pdf 2 Docklight Application Note Docklight Tap Pro and Docklight Tap 485 http docklight de pdf Docklight_Application_Note_TapPro_Tap485 pdf 3 Docklight Tap 485 Product Sheet http www docklight de pdf Docklight_Tap_485 pdf
Download Pdf Manuals
Related Search