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.