MVP 2023 Joe Tauser Posted August 15, 2010 MVP 2023 Report Share Posted August 15, 2010 This is not an easy request, but the problem has come up with several of my customers multiple times. The typical PLC user is not experienced with communication. We have Modbus function blocks for every type of communication, and they individually work great. The problem I have run into with users is you have to write a quasi-driver to use them. Specifically, you have to write logic to handle the interference between reads and writes, and if you're harvesting data from multiple non-contiguous registers or data types from a single slave the timing logic can get really messy. It gets even more complicated with multiple slaves. I propose a data-type table containing slave ID, register address (the real Modbus one, not the -1 offset we currently use), table length, integer or long data type, Unitronics target address, a polling rate for reads, and an MB to trigger writes. Multiple writes could be triggered by the same MB. The handshaking between all these activities would be transparent to the user. This is how every HMI screen I've ever worked with does it. The user never sees the gymnastics behind the scenes to coordinate the multiple read and write requests. Joe T. Quote Link to comment Share on other sites More sharing options...
Emil Posted August 15, 2010 Report Share Posted August 15, 2010 Hi Joe, I hope our R&D will read the topic and will take notes. Meantime - small tip: You can use module "Struct". This module will arrange diferent data types, from different places to one MI vector. I know it's not exactly what you aske about, but in case you want to read/write diferent operands, from different areas, this can simplify sensitivelly the program and, for me even more important - will spead very much the communication. As Modbus is "handshake protocol and each command request confirmation, usually reading 10 registers in one command is much faster than rea"d two registers one by one. Quote Link to comment Share on other sites More sharing options...
Cara Bereck Levy Posted August 15, 2010 Report Share Posted August 15, 2010 Yes, R&D is taking notes. It is a good idea. However--it is August. I placed it as a time-based request, so it will pop up at the beginning of September, when all of the relevant people will be back and normal work resumes... Quote Link to comment Share on other sites More sharing options...
MVP 2023 Joe Tauser Posted August 15, 2010 Author MVP 2023 Report Share Posted August 15, 2010 Yes, R&D is taking notes. It is a good idea. However--it is August. I placed it as a time-based request, so it will pop up at the beginning of September, when all of the relevant people will be back and normal work resumes... Cara- Don't tell me you guys follow the European "we all take a month off in summer" policy. (BTW - to all of you who do this - I am extremely jealous) And that "normal work" thing - can I buy some of that? Joe T. Quote Link to comment Share on other sites More sharing options...
PLC Moderator Posted August 16, 2010 Report Share Posted August 16, 2010 Nah, unfortunately not like in Europe. For one thing, the standard work day is 9.5 hours. But all the kids are on vacation, and by the last two weeks in August all the summer camps have closed down...so a lot of people take off. We won't be starting anything new until everyone is back! Quote Link to comment Share on other sites More sharing options...
External Moderators tmoulder Posted August 19, 2010 External Moderators Report Share Posted August 19, 2010 On a related note, CanOpen could sure benefit from some improved automation. Damian and I were both harping about having to essentially write a driver from component parts to assemble a motion control method. If only there were some standard that emphasized motion control over CanOpen, and had pre-configured PDOs for communicating with drives directly... Oh, wait - there is! DSP402! That would surely help us CanOpeners over here Thanks! TM Quote Link to comment Share on other sites More sharing options...
MVP 2023 Joe Tauser Posted August 20, 2010 Author MVP 2023 Report Share Posted August 20, 2010 On a related note, CanOpen could sure benefit from some improved automation. Damian and I were both harping about having to essentially write a driver from component parts to assemble a motion control method. If only there were some standard that emphasized motion control over CanOpen, and had pre-configured PDOs for communicating with drives directly... Oh, wait - there is! DSP402! That would surely help us CanOpeners over here Thanks! TM Tim, there already is a standard tool for CanOpeners- Joe T. Quote Link to comment Share on other sites More sharing options...
External Moderators tmoulder Posted August 20, 2010 External Moderators Report Share Posted August 20, 2010 PPHPTT! Quote Link to comment Share on other sites More sharing options...
Damian Posted August 20, 2010 Report Share Posted August 20, 2010 Tim, there already is a standard tool for CanOpeners- Joe T. Enhanced model Quote Link to comment Share on other sites More sharing options...
Cara Bereck Levy Posted August 30, 2010 Report Share Posted August 30, 2010 Okay--the topic was raised. We cannot implement it currently, but will in the next generation. Quote Link to comment Share on other sites More sharing options...
External Moderators Nacho Posted August 31, 2010 External Moderators Report Share Posted August 31, 2010 I wondered about that when I saw the Modbus Protocol first time. Maybe because I was using a lot of HMIs with that way of work. It would be a wonderful tool for newbies in communications. By the way, I've spent my three weeks of summer holidays and I can say it's not easy to work at 40ºC in the streets. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.