Internet PLC Forum

For Gary,

I am an 'old guy' too, keeping 200 of the PLCs working.

Thanks for the comprehensive response. I really appreciate the time you have given this.

I don't think the problem is the update ripple. The log below is the time-stamps from an hour of responses  from midnight. As the log is sequential in time, as received, you can see the problem individuals.
;2016/11/15 23:57:20;
;2016/11/15 0:1:46;
;2016/11/16 0:2:57;
;2016/11/16 0:6:10;
;2016/11/16 0:8:58;
;2016/11/15 0:11:39;
;2016/11/16 0:12:11;
;2016/11/16 0:15:29;
;2016/11/16 0:16:16;
;2016/11/16 0:21:27;
;2016/11/16 0:22:7;
;2016/11/15 0:22:51;
;2016/11/16 0:22:33;
;2016/11/16 0:26:26;
;2016/11/16 0:28:33;
;2016/11/16 0:43:23;
;2016/11/16 0:52:10;
;2016/11/16 0:54:13;
;2016/11/16 0:54:1;
;2016/11/16 0:55:44;
;2016/11/16 0:57:29;
;2016/11/16 1:8:14;
That night there were 3

I will try some comparisons, but I suspect the problem isn't transitory but some mechanism in the firmware is delaying the date update till up to 25 minutes after midnight. I never see the problem after about 25 minutes after midnight.

The easy work-around is in the server, simply disbelieving timestamps that are close to exactly a day out for 30 minutes after midnight. I get another report at midday where this problem doesn't happen so can do real updates then.  It is, however, an effect that would be good to understand better.

I have a number of FMD88-10s with the FRAM-RTC that report at 12 hour interval to a proprietary server at a central site over the Ethernet connection. Part of the report string is a time-stamp string, generated as below (the format being for Excel)

   H$ = LOCSId$ + ";" + STR$(DATE[1]) + "/" + STR$(DATE[2]) + "/" + STR$(DATE[3]) + " "
   H$ = H$ + STR$(TIME[1]) + ":" + STR$(TIME[2]) + ":" + STR$(TIME[3]) + ";"

Occasionally, if the report happens between 00:00 and about 00:30, the day field (DATE[3]) remains the previous day. I haven't been able to characterise this. It certainly is not every report and only some sites.

The segment below is  from a log, the site, among 15 others reporting the date as the 13th, reports the 12th. Previous log at midday on the 12th for this site contained the correct date, as did the log before that at 00:00 on the 12th.

          ;2016/11/12 0:22:47;

Question is, does the day field of the DATE variable take some time to update after midnight? Can I spot this happening or do something to avoid it?

We are about to embark upon a software update of over 150 sites. Is there a more automated or possibly command line loader available to help with this task?

Hi,

We are using the FMD88-10 in about 80 sites to report sensor data up to a central server. Communications is via the ethernet port and, mostly, a 3G modem/router. I use TCPConnect to establish a session to the central listener and a PRINT$ to transfer a data string then close the session. This every 2 minutes. It is generally successful.

I recently attempted to add a second data message into the session. This consistently fails at a number of sites. It seems those that fail are the sites where the ACK for the first data message takes longer than about 500mSec.

If I start Trilogy and On-Line monitoring to the site, the problem drops to only a small number of transmissions though.

I have included a .jpg of a trace from Wireshark, obtained with a SharkTap connected to the Ethernet port of an FMD-10 where I have the problem.

It appears to me that the second PSH is sent (line 5) with the sequence of the first if the first has not received the ACK (arrives in line 6).

I really need a workaround or suggestion as to how I can avoid this problem. I have tried a number of mechanisms but with no success.

I can provide Wireshark traces of a number of the failed messages if that would be of use.

Thanks

I am running a Modbus with multiple slaves from an FMD88-10 RS485 port 2 which is the master.  Bus speed is 9600. The various slaves are polled by custom functions triggered by separate  timers. Occasionally I have a poll that doesn't get a response.

Looking at the bus on an oscilloscope, The missed responses happen when the poll goes out in less then the modbus 3.5 character IFG from the preceding response. The slave device misses the poll as it is not separated from the last frame on the bus by the 3.5 character IFG.

My question (which I hope isn't a case of RTM) is, do I need to ensure the calls to READMB2 are separated by the Modbus minimum 3.5 character IFG? This is not done by the FMD protocol layer?

I am using the FMD88-10 in a number of sites. One function is to act as Modbus master to a number of slave devices. One of the devices I also access (for diagnosis) using the gateway function from the TCP port. This works fine with read register (03) and write registers (06, hex 10) function codes. I am also using the EIT function code (hex 2B). This is transferred to the 485 bus from the IP successfully but when the device responds, only a single byte, the address is transferred back to the IP side. Question, is the gateway function only available for the modbus register read and write commands? I am hoping the gateway wasn't interpreting function codes.

Second gateway question. The device responds to an unimplemented function code (03) with an exception code of 01. The seems to be translated in the gateway to hex 0B. Is this intended?

Thanks for the help