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TMS320F28375S: TIDM- SOMPLC-F28PLC90. PLC Communication Problems

Part Number: TMS320F28375S

Hello,

We are using one of your obsolete SOM-PLC Communication solutions and we’ve detected communication problems when we increase the number of Service Nodes in the PLC line, from 2 to 4 Service Nodes. We’ve observed unexpected issues like delays in the PLC-Module transmissions to our Host or failure status in data transfer transmissions  (problems described below). We hope you can give us some support.

  • Modem:
    • Hardware: TIDM- SOMPLC-F28PLC90. Microcontroller: TMS320F28375S and TMS320F28377S.
    • Software: G3_SDK_Package_V7_7_6_6.
    • PLC Suite G3 Host Message Protocol Specification version 2.0.29 as reference.

  • Communication characteristics:
    • 1 Base Node and 4 Service Nodes.
    • Data transmission windows defined by the application to avoid collisions between different nodes of the network (customer requirement):

Base Node

Service Node 1

Service Node 2

Service Node 3

Service Node 4

SPARE

Base Node

Service Node 1

0 ms

50 ms

100 ms

150 ms

200 ms

250 ms

300 ms

350 ms

  • PLC configuration (initial):

    • Device Mode=0
    • TMR=0
    • COH=0
    • Band Sel= 0
    • TX Modulation=0x01 (BPSK)
    • TX Level=32
    • Tone Mask= 0x 21.48. ff.ff.ff.ff.ff.ff.ff.ff.ff.00.00.00
    • TX Gain/Attenuation= 30 (hx1E)
    • TX PGA Attenuation= 0 (hx00)
    • macMaxCSMABackoffs= 1
    • macHighPriorityWindow Size=1
    • adpmaxhops=1
  • PLC Issues:
    • Delay in DATA_TRANSFER.confirm: We have detected long times (more than 500 ms) since the Host sends a DATA_TRANSFER.request until the PLC Module sends back the confirmation DATA_TRANSFER.confirm. We need to reduce this time so we tried to disable the medium access control (MAC) mechanisms, changing the following parameters:
      • macMaxCSMABackoffs = 0
      • macMinBE = 0
      • macMaxBE = 0

Unfortunately, we still have significant delays which don’t fulfil the transmission windows requirement (see the table above). We even get this delays with only one Base Node connected and none Service Node on the line.

    • Unexpected status in DATA_TRANSFER.confirm: Sometimes we receive the value 0x20E1 as status in DATA_TRANSFER.confirm, according to section 4.5 of “PLC Suite G3 Host Message Protocol Specifications” this error code means: G3_ERROR_CODE_MAC_GROUP + MAC_STAT_CHANNEL_ACCESS_FAILURE. We understand this error as a channel access failure of the CSMA-CA algorithm (according to the standard ITU -T G.9903). As the previous issue, we also get this failure with only one Base Node connected and none Service Node on the line.
    • LED behavior: We have observed that the LED at the PLC Module connected to GPIO41 of the microcontroller, which is normally blinking (1sec period), stop blinking (sometimes remains OFF and some other times remained ON). Is this LED representing the System Heart Beat of the PLC Module?
  • SNR Level: We would like to know a range of valid SNR values which assures a stable and robust PLC communication. Has the SNR level any influence on the issues related to DATA_TRANSFER.confirm (delays and failures)?
  • Test Points: The PLC board includes several test points. Could you provide documentation or any information about these test points? Is there any test point that provides information about MAC or VCS (Virtual current Sense)?
  • Source Code: We’d also need the PLC FW source code and/or its documentation.

Thank you.

  • Victor,

    I'm going to reach out to some of previous module owners to see what information I can get regarding this SW/HW package.  I'll provide another update by tomm EOB.

    Best,

    Matthew

  • Victor,

    Updating the post, I'm working off forum with the local TI representative to determine the best course of action here.  Most likely we will be in contact with you off-line, but will update here if that is not the case.

    Best,

    Matthew

  • Thank you Matthew. I await your reply.

  • Hi Victor,

    Matt is currently unavailable and may not be able to get back to you until the middle of next week.  I'm sorry for the delay and thank you for your patience.

    Regards,

    Joe

  • Victor,

    Checking in to make sure you have gotten contact with your local TI applications engineer.  He will be providing you with the next steps we'd like to take to help resolve this.  Please let me know if this is not the case.

    Best,

    Matthew

  • Hello Matthew,

    I have no news about this issue yet. No one has contact me in the last days.

    Regards,

    Víctor

  • Victor,

    Thanks for reaching out I have received the requests yesterday afternoon.  They have both been approved from my side, based on past experience you should be getting an approval email today.

    Will keep this post open so you can let me know if you see it or not by tomm at the latest from us.

    Best,

    Matthew

  • Hello Matthew,

    I have access to download two SW packages but I have some comments:

    • I'm missing any information or documentation which helps to understand the packages provided. Could you please provide any information about it and its folder distribution? We would like to build it in a CCS project.
    • I see the version of both SW packages provided (v7.8.x.6 and 7.8.x.4) are different from the version we asked for (v7_7_6_6).
    • We use an external Host to manage the PLC-Modem and we required the SW of this Modem. I understand that the SW package needed is the Service Node SW right?
    • Do you have any information about the rest of the issues at the first post?

    Thank you for you support.

    Regards,

    Víctor Lema

  • Victor,

    I'm going to reach out to you off forum since there are quite a few pieces to this FW/documentation that likely will need to be shared.  I'm going to leave the E2E post open for now as a placeholder as we work toward resolution.

    Best,
    Matthew