Troubleshooting the CAN I/O bus with SMC-42.
Contents
1. Error messages C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 13 of 13 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 5 Filtering the CAN messages after a system error In the case of a system error on the CAN I O bus from SMC 42 system version 8 the most recent messages can be viewed in plain text and various filters used After the system error message first one of the arrow keys HIGH or LOW key is pressed to display blocks of 12 messages in steps of 1 10 or 100 A number be tween 0 and 5 is then entered for the filtering On the entry of the number 0 mode 0 is selected Here all CAN messages are displayed in plain text as previously If a number between 1 and 4 is selected the ID numbers 1 to 127 for the module to be found must be entered and confirmed with Then only the CAN messages from and to the CAN I O module with this ID are filtered To display these messages one of the arrow keys HIGH or LOW key must be pressed again If the number 5 is entered then the error messages for all modules are displayed The following table shows the allocation of the filter properties Mode Filter 0 none 1 ID all messages 2 ID input messages 3 ID output messages 4 ID error messages 5 all error messages The2. CAN message filter is very recommendable to ensure that modules are not re placed unnecessarily due to error messages from them as a consequence of other errors that have occurred on the CAN I O bus C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 14 of 14 08 03 05 PH
3. The last difference signal in a CAN message is the so called ACK signal and this is confirmed by all CAN modules on the bus The difference voltage for the ACK signal is thus greater than the voltage for the previous signals This example was produced with a baud rate of 125 kBit The storage CRO used was a LeCroy with a 2 5 Gbit sampling rate The setting for the voltage level and the trig gering can be seen in the figure C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 3 of 3 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 3 Measuring the wiring and screening 3 1 Measuring the wiring The following measurements are made using a suitable Ohmmeter measuring range lt 2000 between two CAN connectors on the ends of the cable CAN_24V Pin 1 at the start of the cable to pin 1 at the end of the cable CAN_L Pin 2 at the start of the cable to pin 2 at the end of the cable CAN_OV Pin 3 at the start of the cable to pin 3 at the end of the cable CAN_H Pin 4 at the start of the cable to pin 4 at the end of the cable Measuring arrangement Start of the cable End of the cable Auxiliary wire Figure 2 Measurement of the cable resistances The resistance measured is the sum of the resistances in the connector approx 10 30 milliohm connector and the
4. cable resistances The CAN cable used has a resis tance of around 160 milliohm m For a 30 m long cable around 4 8 to 5 8 Ohm will be measured on the CAN_H and CAN _L wires depending on the number of modules It is to be noted that the CAN_H and CAN_L wires are only single wires and the CAN_OV and CAN_24V wires are duplicated this results in the halving of the resis tances of these wires If a CAN repeater has been used the CAN_H and CAN _L wires should be measured before and after the repeater because the repeater electrically isolates these wires The CAN_OV and CAN_24V wires bridge the repeater C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 4 of 4 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 3 2 CAN repeater The electrically isolating CAN repeater transmits and amplifies the CAN signals The bus input and bus output wires are each terminated with a 1200 resistor D SUB 9 pin 2 to pin 7 The CAN_OV and CAN_24V wires and the screen are wired through directly and reservoir capacitors are arranged between the CAN_OV and CAN_24V wires Bus input gt u CAN_2 Bus output Connector 2 Connector 3 female male Screen Pin Identifier Function 2 CAN L CAN data wire gt dominant low 3 CAN_OV Ground 7 CAN_H CAN data wire gt
5. dominant high 9 CAN_24V Positive supply 24V Figure 3 CAN repeater C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 5 0f5 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 6 of 6 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 3 3 Measuring the terminating resistors Measuring arrangement CAN plug Figure 4 Measurement of the terminating resistors Start ofthe cable End of the cable Terminating SMC 42 CAN repeater resistor Figure 5 120Q terminating resistors The terminating resistors at the ends of the wires are 1200 On a measurement with a CAN repeater approx 60 Ohm will be measured on the bus input and bus output if the CAN circuit is not open All measurements must be made with the system switched off C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 7 of 7 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 3 4 Measuring the
6. screening The error that occurs most frequently is inadequately tightened CAN connectors on the modules or that the cable fitting on the connector for connecting the screen is not tight enough The measured resistance between the CAN bridges from one module to another should be less than 0 4 Ohm Figure 5 Measuring the screening If the resistances measured are higher you should tighten the connector on the CAN cable Good screening significantly increases the immunity of the CAN I O bus to interfer ence C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 8 of 8 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 4 Known problems and solutions For the CAN I O bus to function correctly several prerequisites must be met 1 The declarations for the CAN I O modules in the SMC 42 program must be made in the same order as they are wired 2 The declaration for the baud rate must be the same in all modules 3 The CAN cable must be screened the CAN connector on every module tight ened and a connector with the terminating resistors must be fitted atthe end of the bus on the last module Despite these measures defective cables CAN I O modules missing terminating resistors or poor screening can cause problems 4 1 SMC 42 program The SMC 42 p
7. 409 00409 lt ID8 T2 10441 00441 END_CAN DEVICE The character lt inserted at the start of the line allows the inputs and outputs to be used in the SMC 42 program without the generation of error messages by the com piler however the bracketed out modules are not taken into account when starting up and operating the CAN bus In this way it is possible to place individual modules in operation one after the other or in the case of electrical problems to switch in indi vidual cables and modules in succession For this reason it is strongly recommended to list the modules in the CAN_DEVICE program block in the order in which they are actually wired 4 1 4 CAN_ON and CAN_OFF commands These commands are used for switching on and off the CAN I O bus If a module is missing the system error 59 CAN missing modul at ID is triggered immediately with the ID number 4 1 5 CAN_CHECK command Using this command the frequency of the periodic check on all CAN I O modules is defined Example CAN CHECK 5 CAN _ON On the failure of a module while the bus is in operation the system error 53 CAN timeout error at ID is triggered with the ID number C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 11 of 11 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch c
8. EVICE declaration For each individual module the module number the module type the assignment of the first input and the first output must be specified in the SMC 42 Example CAN DEVICE D1 T0 10193 00193 D2 T0 10201 00201 D3 T1 10209 00209 D4 T1 I0217 00217 D127 T4 10281 00281 starter box D63 T2 10287 00287 D56 T2 10409 00409 ID8 T2 I0441 00441 END_CAN DEVICE Comment ID1 is the module number 1 TO is the module type with 8 inputs and 4 outputs T1 is the module type with 4 inputs and 8 outputs T2 is the module type with 24 outputs T4 is the module type with 8 inputs and 8 outputs 10193 is the number for the first input on module 1 00193 is the number for the first output on module 1 If the module type is incorrectly stated the system error 51 CAN modul_type error ID is triggered with the ID number C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 10 of 10 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch On start up or troubleshooting on the CAN I O bus you can bracket out the modules that are not yet connected to the bus Example CAN DEVICE ID1 T0O 10193 00193 ID2 T0 10201 00201 lt ID3 T1 10209 00209 lt ID4 T1 10217 00217 lt ID127 T4 10281 00281 starter box lt ID63 T2 10287 00287 lt ID56 T2 10
9. Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch Troubleshooting the CAN I O bus with SMC 42 Troubleshooting sporadic errors on the CAN I O bus is relatively difficult and time consuming These instructions provide information on the various possible tech niques that have proven useful in practice Troubleshooting measures are suggested here If the CAN I O bus is functioning correctly you will not find any error messages in the CAN statistics in the service mode The service mode can be opened from the man ual mode and the statistical data for each CAN I O module viewed On the occurrence of problems the analogue signals on the CAN bus should be checked and analysed with a CRO The SMC 42 program must be checked for correctness or modified for specific test methods Measurements on cables screening and terminating resistors are very important Table of contents 1 Selecting service Moden an ets cai ee at le a ie ee a fa i ee 2 2 CAN_H and CAN L signals on the CRO uunnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nenn 3 3 Measuring the wiring and screening ccccceeeeeeeeeeceeeeeceeeeeeeeeeeeeaeeeeeeeeeeeeenee 4 3 1 Measuring the MINING eect it see ee 4 a2 GAN repe A O 2 asc kim Eee 5 3 3 Measuring the terminating reSiStOrs ccceceeeeeseeeeeceeeeeeeeeeeeeeeeeeeeeeeeeeeens 7 3 4 Measunng ihe sereenind a c eseineeekesheke
10. de You can only switch to the service mode from the manual mode To start the service mode press the SHIFT and 6 keys in succession The ESC MAN and STAT LEDs illuminate to display the service mode To open the statistics on the CAN I O modules press the RIGHT gt key The statistics for the first module in the CAN_DEVICE table are displayed E g SERV left right exit with ESC UP DOWN 1 HIGH LOW 10 INDEX 0 IDENT 4 M ERR 0 MESGS 543211 REPEAT 0 EMERG 0 You can access the next or previous I O module or its I O group in steps of 1 using the UP and DOWN keys Using the HIGH and LOW keys you can access the next or previous I O module or its I O group in steps of 10 The I O group is identical to the module for the module types TO T1 and T4 Module type T2 has 3 I O groups because it contains 24 outputs Each I O group represents one I O byte The only difference is the higher INDEX with the same iden tifier ID The INDEX is formed on the initialisation of the CAN I O bus as per the se quence of the modules in the CAN_DEVICE table and is incremented for each I O group IDENT is the identifier for the indexed I O group M_ERR is the maximum number of the same messages that have been repeated for the related I O group These error messages are sent by the I O group if the outputs have been overloaded or short circuited MESGS is the total number of outgoing messages to the related I O group since the CAN I O bu
11. h 4 2 System error 58 The causes are Defective drivers on the front panel of the SMC 42 No modules are connected Incorrect baud rate Short circuit or open circuit on the bus The system error message 58 indicates the CAN I O bus error status in which the error status of the status register in the 82527 controller is reflected BIT 7 6 5 4 3 2 1 0 Name BOff Warn Wake RXOK TXOK LEC2 LEC1 LECO Table 1 Status register for the 82527 CAN controller The significance of the individual bits is given in detail in the data sheet on the 82527 An abbreviated version of the significance of the bits in the system register follows BITS NAME _ Significance 7 BOff 0 CAN bus is switched on 1 CAN bus is switched off because of more than 256 errors 6 Warn 0 less than 96 errors on the CAN bus or none 1 warning more than 96 errors on the CAN bus Wake_ sleep mode switchover RXOK 1 last message received without errors TXOK 1 last message sent without errors 0 2 LECO 2 0 no error 1 stuff error more than 5 bits the same in the message 2 shape error incorrect format of the message received 3 Ack error no CAN I O module has received and acknowledged the message sent 4 bit 1 error it was not possible to send the last message 5 bit 0 error own message read incorrectly 6 checksum error oO oO Table 2 Bits in t
12. he status register in the 82527 CAN coniroller Example p_index 00000000 CAN OFF STOP at system error NR 58 CAN 8257 error status STATUS 43HEX 67 The STATUS 43HEX signifies that the bits 6 1 and O 3 are high The 3 indicates an ACK error if e g there is no CAN I O module connected to the bus C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 12 of 12 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 4 3 Missing modules Missing or incorrectly configured modules type are indicated with the system errors 59 or 51 when the CAN I O bus is started 4 4 Malfunction or short circuit on the output of a module If there is a short circuit on the output of a module or in the event of synchronisation problems on the CAN I O bus error signals from the individual modules are received in SMC_42 this results in system error 52 after more than 8 error messages from the same module in succession In the case of occasional error messages a system er ror is not triggered However the error messages are totalled for each module and appear in the error statistics 4 5 Short circuit on the input of a driver Such an error can only be detected with the CRO In this case one of the two differ ence signals CAN_H or CAN_L is short circuited The consequence i
13. nulekebeisshleig 8 4 Known problems and solutions uuusssnsssnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn nn 9 4 1 sSMG 42 Program endende kenne ee ee 9 4 1 1 Baud rate declaration 422444440004nnHHnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 9 41 2 LIMIS declarationis ia 10 4 1 3 CAN_DEVICE declaratlonints suc seem ae 10 4 1 4 CAN _ON and CAN_OFF commands 2220u0sssssnnnnnsnennnnneeennnnnnnnnn 11 4 1 5 CAN CHECK COMMand cccccccccssssseeeeeccecseccessseeeeeeeeeessecasseseeeeees 11 4 2 System error 58 2 else agree Spite 12 4 3 Missing ModUles asensersnssns en aan Hs 13 4 4 Malfunction or short circuit on the output of a module 2222 13 4 5 Short circuit on the input of a driver 22244400uunnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn 13 4 6 Summary of the system error MESSAGES uuuuussensnsssnnnnnnnnnnnnnnnnnnnnnnnnnn 13 5 Filtering the CAN messages after a system error uusssssssssssennnnnnnnnnnnnnnnnnn 14 C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 1 of 1 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 1 Selecting service mode The statistics on all CAN I O modules that have been declared in the CAN_DEVICE table can be opened in the service mo
14. rogram is checked by the compiler to ensure that no inputs or outputs can occur in the program that are not declared as local and extended inputs and out puts Extension I O or as CAN I O inputs and outputs With one exception bracket ing out of the modules with the lt operator or the usage of the command CAN_CHECK 0 the CAN I O modules are also continuously monitored for their presence The most important language elements are BIT RATE LIMITS CAN DEVICE END CAN DEVICE CAN ON CAN OFF CAN CHECK The significance of these commands can be found in the SMC 42 manual A brief explanation follows 4 1 1 Baud rate declaration At the start of the SMC 42 program the baud rate on the CAN I O bus must be de clared Example BIT RATE 125k All modules must be pre programmed for this baud rate The CAN I O bus cannot be started if this condition is not met C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 90f9 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 4 1 2 LIMITS declaration Example LIMITS SMC1 11001 1192 01001 1192 F1001 2000 D1001 1320 CI1193 1872 C01193 1872 T6 24 X5 Y6 518 W44 J31024 G647 These include LOCAL INPUTS O LOCAL OUTPUTS Cl CAN BUS INPUTS CO CAN BUS OUTPUTS G CAN BUS DEVICES 4 1 3 CAN_D
15. s an accumula tion of error signals from the CAN modules that have problems with synchronisation The module with the faulty driver is identified using a modified SMC 42 program in which e g all modules except for the first two are bracketed out The terminating resistor is connected to the second module and then the CRO image should corre spond to the signal curve shown in Figure 1 Further modules are then connected electrically until the faulty module is found Only when all other modules except the faulty module are re connected and the CRO signal corresponds to that in Figure 1 can the faulty module be replaced with certainty 4 6 Summary of the system error messages The SMC42 operating system generates the following system error messages No Error message Significance 51 CAN modul_type error ID _ Incorrect module type declared in CAN_DEVICE 52 CAN error message at ID Malfunction in the CAN I O module or short circuit 53 CAN timeout error at ID CAN I O module no longer responds 54 CAN unknown modul at ID Module not declared in CAN DEVICE 55 CAN return error at ID Incorrect message from CAN I O module 56 CAN transmt buf overflow Transmit buffer full 57 CAN receive buf overflow Receive buffer full 58 CAN 82527 error status CAN I O bus error status 59 CAN missing modul at ID Missing CAN I O module 61 wrong CAN identifier Missing CAN I O module Table 3
16. s was switched on using the CAN_ON command REPEAT is the total number of repeated messages EMERG is the total number of error messages for the related I O group if the I O module was not able to synchronise itself on the CAN I O bus M_ERR REPEAT and EMERG must be equal to ZERO for correct operation On all modules with version 1 2 or 3 year of manufacture 1999 REPEAT is allowed to be gt 0 C Dokumente und Einstellungen rainer_poelzl Eigene Dateien HE_Doku englischOriginal T04652_en_ 1_Teil TEST_CAN_SMC42_en doc Page 2 of 2 08 03 05 PH Horsch Elektronik AG 9473 Gams Switzerland http www horsch ch Tel 41 81 771 61 81 FAX 41 81 771 17 47 e mail info horsch ch 2 CAN_H and CAN_L signals on the CRO 14 Nov 01 TRIGGER SETUP 11 29 45 SMART 2 C trigger on 1 2 Ext Ext10 Line coupling 1 AC LFREJ HFREJ HF slope 1 ZE Neg Window holdoff Time a 50 ps 2 00 V 1 50 ps 2 00 V re rey 2 EEE es DE E 50 ps 2 V OC x l i 50 MS s 2 2 V DCX nm 1 DC 3 24 v O STOPPED Figure 1 CAN bus signals on the CRO In the figure above CAN_H channel 1 CAN_L channel 2 signals and their differ ence calculated channel A are shown With a dominant signal the difference be tween CAN_H and CAN _L must be more than 1 5 Volt 1 5 to 3 Volt according to the line driver data sheet With a recessive signal the difference voltage is equal to zero
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