AdvancedHMI Software

General Category => Support Questions => Topic started by: bubulindo on January 23, 2018, 02:47:02 PM

Title: Modbus TCP driver behavior
Post by: bubulindo on January 23, 2018, 02:47:02 PM

Hello,

I'm trying to get Modbus TCP working with an ESP8266 and not getting much luck. So before digging into the ESP8266 Modbus implementation, I'd like to know a couple of things about how the Modbus driver works.

Does the driver open and close a connection on each transaction or is it expecting the connection to remain open?

Is it smart in the sense of grouping addresses in order to minimize the requests or does it make a single request per variable defined?

Title: Re: Modbus TCP driver behavior
Post by: Archie on January 23, 2018, 02:55:18 PM

It keeps the connection open. It will group subscriptions to optimize reads. This is controlled by the MaxReadGroupSize property.

Title: Re: Modbus TCP driver behavior
Post by: bubulindo on February 12, 2018, 06:33:38 PM

Thanks Archie,

As suspected, the issue was on the ESP8266 side as the library I was using closed the connection no matter what. That's half fixed now and displaying stuff on the HMI now.

Title: Re: Modbus TCP driver behavior
Post by: bubulindo on February 12, 2018, 06:37:14 PM

One more question, I worked in the past with a topology for manually controlled equipment that relied on UDP telegrams to get data over to the HMI. It was the basic example of when to use UDP vs TCP applied to controls and I was wondering if there's anything like this in Advanced HMI.

I understand that it would be trickier to implement, but on Siemens controllers is fairly easy to configure and transmits an awful lot of data in one go.