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Dears, have someone solved problems for the connection  between a CR1000 Modbus slave and a SCADA master connected by radio? I have two generic radio modem that make this connection (basically a virtual cable) with LoggerNet/pakbus everything works, but when I replace LoggerNet with Modbus SCADA or a SW that simulates the Modbus master, the communication does not work. If I eliminate the virtual cable generated by radio, and connect the CR1000 directly to the SCADA the communication works fine, and then the various registers are displayed and updated. Baudrate is 9600. What I have noticed with radio is that LoggerNet variables in numeric are updated very slowly, around every 20..30 seconds.
Do you have suggestions or informations?

Thanks in advance
Smile

Dears now I have the radios in office and I can perform some tests.

The problem there is when I use the port COM4, since when I use the port RS232, all works fine (Modbus and Pakbus).

Something does not convince me, because with the COM4 and Pakbus all works fine.
I was able to test even with the radio CSL mod. RF416 and with these radio works all (both Pakbus and Modbus). Unfortunately I can not use these radios in situ because I have problems with 2.4 GHz.
Anyone have any idea? With a sniffer I want understand if the CR1000 logger does not answer for a modified Modbus string incoming or logger responds too quickly and the radio does not transmit.
In the CR1000 code I have also entered the serialOpen instruction to generate a delay before TX but does not seem to work, I can greatly increase the delay value but I see the TX red LED that lights up immediately after the green LED RX without delay (also if delay is some seconds).

Many thanks

Regards

Smile

Dears. I have news! (no good)

I also tried with a CR6, using C3 / C4 but behaves the same way.

Essentially the logger, always comes this HEX string (without quotes):
"01 03 00 00 00 10 06 D44"

If this string comes on the RS232 port always works, radio-modem, RF416 or wired, the logger responds and SCADA receives the data properly.
If the same string arrives on COM4 of the CR1000 via wire or RF416 logger responds and SCADA receives the data correctly, if I use the radio-modem, the string comes but the logger does not respond

Thanks again to those who could give me a suggestion for other tests.

Regards

Smile

The issue is that delay between characters will cause a Modbus packet to timeout. If your radios break the packet into two separate radio packets, Modbus will fail.

Modbus is particular about radios because of this.

Dear JDavis,

thank you very much for your interest in this problem.
For me it is a nice puzzle.
What you have described more or less, about I had reckoned, although I could not verify it.
But what I do not understand why with the RS232 port, everything works!
The radios are always the same, as well as the Modbus master that sends the requests. Unfortunately I was in a hurry to install the system by the customer, and we decided to use the RS232 port.
Soon I take other radios for continue with more time, the other tests. Before that, perhaps the customer might get annoyed, when locally goes to the station and need to exchange the RS232 port between the radio and the laptop.

Thanks again

Regards

Smile

For radios to avoid character delays problems in Modbus, they have to do one of these things:

1. Transmit over the air at a faster rate that the RS232 port.
2. Use packet recognition to hold unto a message until all the data is ready to output out RS232

RF416 are packetized. RF422 should also work is legal in your country.

Thanks a lot, I'll keep these rules in mind.

Smile