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Author Topic: Modbus and Vera.....is it possible?  (Read 6523 times)

Offline TimAlls

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Modbus and Vera.....is it possible?
« on: March 20, 2011, 12:35:43 pm »
In my industry of yacht building we interface with hundreds of different industrial modules such as Adam Modules with eight analog inputs or eight temperature inputs Etc.....
It seems to me that many users out there are coming up with the need to monitor all sorts of unique devices. Modbus TCPIP devices are fast, fairly cheap, and would allow any type of monitoring you can imagine. For example, I use a power meter that cost $149 dollars and it has Modbus built in. This allows me to monitor amps, volts, frequency, total power used and lots more.
Perhaps if enough responses came from this blog then the folks at vera might add the protocol to the list of Veras capabilities.
What do you think?
Thanks
Tim Alls
AllSeas Yachts

Offline guessed

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Re: Modbus and Vera.....is it possible?
« Reply #1 on: March 20, 2011, 01:23:40 pm »
There was an early discussion on this, but don't think it evolved:
    http://forum.micasaverde.com/index.php?topic=2907.0

The biggest challenge you're going to run into is that Modbus is (or appears to be) poll-based, not event-based.

Poll-based entities need to be polled frequently, and this doesn't scale out well [resource wise] as the number of devices increases.

For Event-based devices (like Alarm systems, Z-Wave, etc, etc) they tell you when a significant value changes, using a pseudo-reliable event mechanism.  You typically get much lower event-traffic, since you're only seeing "change" events.

If you were going to build out a Modbus-plugin, the biggest challenge would be in running it's Poll-loop fast enough to ensure you don't miss events.

It's not clear whether Vera would be fast enough to do this acceptably for low-level, high-change, sensors.

MiOS itself is setup fairly well for Event-based devices, and a number of people are experimenting with various IO devices that work well in this model (GC100, SerIO, and various other Ethernet-attached IO devices)

If someone built a hardware Modbus (Poll) -> Event converter, then it could be inserted in the middle to eliminate the need for Vera to poll, but I've not seen one of these (I looked some time back)



In the next few months, I'll integrate a resource that sends [event-change] messages, 1 per second, and I suspect even this will "stretch" Vera, given the other things I've got going on in my system.
« Last Edit: March 20, 2011, 02:17:23 pm by guessed »

Offline TimAlls

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Re: Modbus and Vera.....is it possible?
« Reply #2 on: March 20, 2011, 03:02:44 pm »
I see your point and I am seeing that the vera is operating on a minny resource system! I think your idea of a polling device that works along side Vera is a good one. I was also thinking that mini pc's sell for $100 dollars at Fry's Electronics. One could easily switch to  a Linux operating system and have plenty of stregnth to handle polling. I know because I am doing it now with Labview and I have 24 hour trend charts running and much more.
Perhaps it is stretching the limits of the Vera to head in this direction but once you get used to notifications coming in from Vera it begins to spark your imagination with ideas on the things you could do!
Some of the newer mobus modules do have logic events built into them...EG if a level goes above a certain value then turn on another modbus digital module or address. What would be nice is the Vera III.....a more expensive system built on a better frame with more resources! For those of us with bigger budgets and more things to do......
Food for thought!
Regards
Tim Alls
Allseas Yachts

Offline guessed

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Re: Modbus and Vera.....is it possible?
« Reply #3 on: March 20, 2011, 03:18:22 pm »
Yup, those in the Beta forum know me as a long-term proponent of a much more resourced MiOS device.... one that could support a broader array of functions, as well as more Real-time processing and greater stability to those with larger configs for a relatively incremental cost over the current Vera units.  Of course, there are some very real-world considerations also (Production volumes, reliability of source-vendors, time to procure, testing, etc, etc) so it's not a one-sided discussion ;-)

Unfortunately we're not winning that battle.

I recently purchased a compact Linux device to "offload" some of this workload from Vera, esp wrt long term [localized] archival and graphing of historical data (probably RRDtool based) - independent of the MiOS servers.

I'm also considering using it to provide a custom iPad-based [HTML/Javascript] UI that I'll build - at least until one of the CP vendors builds a suitable one to replace it.

It's surprising how much power you can get in a cheap ($140) device, and there are a bunch of these floating around these days without needing a PC.

eg. Gb Ethernet, 1.2GHz ARM processor, 512M RAM, 512M Flash, Bluetooth, native Z-Wave, Wifi, 2x USB...
« Last Edit: March 20, 2011, 04:01:57 pm by guessed »

Offline skoumaiha

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Re: Modbus and Vera.....is it possible?
« Reply #4 on: September 30, 2014, 07:20:53 am »
Is there a ModBus/Zwave gateway available in the market?