EPOS2 / EPOS4: Serial data frame error messages (USB / RS232)

Topic:

• What are typical root causes of the "EPOS Command library" error codes refering to "Serial data frame" errors (code: 0x3400 0006 or 0x3400 0007)?
• What has to be checked in case of "Serial data frame" error states?
• Which measures have to be taken into account in case of "Serial data frame" error messages?

Situation:

An application program uses the "EPOS Command Library" in exchange data and command an EPOS2 or EPOS4 by USB or RS232. There are sporadically "Serial data frame not written" (Abort code: 0x3400 0006) or "Serial data frame not received" (Abort code: 0x3400 0007) error messages present during operation.

Solution:

Both mentioned error messages 0x3400 0006 ("Serial data frame not written") and 0x3400 0007 ("Serial data frame not received") are almost ever caused by some signal disturbance of the communication lines.

Especially USB is quite sensitive concerning electromagnetic interference (EMI). Such EMI signal disturbance is possible in case of power cables of inductive loads (like motors) which are too close to the USB cable. Too long (> 3m) USB cables can result in a low signal quality in addition and force communication error states.

RS232/USB converters or USB hubs can be another root cause of sporadically failing data packages which trigger the "Serial data frame" error states.

1.) Cabling in general

Any kind of signal disturbance is often the root cause of communication errors or problems with analog or digital sensor or encoder signal lines. Such signal disturbance is radiated by unshielded motor phase cables (or relay wires) and it can have some bad impact on the signal quality of communication or sensor wires which are too close to the motor cable. Please always take care of the following two general wiring rules:

• Keep power cables away from signal lines
  
  • Power cables of inductive loads (like motors, relays) should always be clearly separated from signal and communicaton cables.
  • Power cables should not be put in parallel to signal and communication cables and not into the same cable channel.
• Usage of shielded power cables
  • In case of inductive loads there should be always shielded cables in use. The shield has to be connected to an Earth potential like described by the following document:
    How to connect a cable's shielding to Earth potential?

2.) USB resp. RS232 wiring

Depending if there is USB or RS232 in use, some additional aspects have to be considered:

USB:

• Recommendation: Cable length < 3m
  
  • Please keep the USB cable short.
    USB cables with a length of more than 3 meters are not recommended.
  • Do not use passive USB cable extensions. The total cable length is the one that counts finally.

RS232:

• Cable quality and wiring:
  • Do not use loose, separate wires but always a multi-core cable instead.
  • GND of the RS232 has to be connected too (and not just the RxD and TxD signal line).

Not sure about your wiring?
Please provide us some photos of the wiring and information about the cable length as well as power components or cables close to it. We will provide some initial judgement based on our practical experience then.

3.) RS232/USB signal converters or USB hubs

If there are any USB/RS232 signal converters or USB hubs in use, try to test without these (if possible) or try to use converters or hubs by a different manufacturer to check if the same communication error messages still occur.

USB hubs are a possible root cause of communication errors.
Not all USB hubs work fully reliable in case of sending and receiving lots of small data packages like present by the communication with motion controllers. The USB hub might bring in some additional signal disturbance or signal delay. Removing the USB hub or replacing it by another manufacturer's type sometimes solved the communication error issue finally and identified the USB hub as the root cause of the error state.

It is also not recommend to use USB hubs in a too cascaded structure one after another because this can increase the risk of signal disturbance and signal delays.

Recommendation:
If you have communication errors present by USB, please try to reduce the number of hubs as much as possible or even avoid these at all.

4.) Motherboard design

If you have designed the motherboard of an EPOS module by your own (instead of using a "Compact" product type), it is important to take care of the general rules concerning separation of PCB's internal signal / communication and the power wires. Otherwise this can result in EMI problems already on PCB level  (similar to external cables too close together).

• Please be aware of the chapter "Motherboard Design Guide" and the information about PCB design and recommended components (incl. motor filters) present by the "Hardware Reference" of any "EPOS Module" product type.

Still running into "Serial data frame" erro messages?

If your system still reports "Serial data frame" communication errors, please submit a support ticket by the Support Center and let us know more details about your system for an in-depth analysis and discussion of your system:

• What concrete EPOS product type (-> part no.) do you have in use?
• Please provide the *.dcf configuration file of your EPOS.
  -> EPOS: Export of parameter configuration in a *.dcf file
• What bus interface (USB, RS232, CAN, EtherCAT) is in use by your system?
• If USB is in use, please provide ...
  
  • ... some information, sketch and photos of the USB wiring and hub structure.
  • ... some information about USB hubs (-> e.g. website link) in use.
• What operating system (incl. version) do you have in use by your PC or master?
  (e.g. screenshot -> Windows system manager -> System)
• What "EPOS Command Library" version do you have in use?
  (-> VCS_GetDriverInfo)
  
  

Cross reference:

• Sporadic USB communication errors 
• EPOS4 / IDX: Action steps in case of failing USB connection