I have intention to try to implement the BACnet MSTP.
I've searched but have not found much.
Does anyone has proven anything about this?
Hello
BACnet is very complicated and time consuming to implement.
My company makes a family of small, low cost embedded and external Gateways to enable new and legacy devices to quickly support BACnet MSTP, BACnet IP, Lonworks, N2 and many other protocols. We can get your products to market with all the BMS protocols in a very short time.
Our BACnet solutions are the only BACnet BTL certified gateways on the market.
Please look at ProtoCessor.com and
Thanks,
Charlie Peterson
Director of Embedded Products
FieldServer Technologies - ProtoCessor
Direct 408-964-4433
cpeterson@ProtoCessor.com
The First BACnet BTL Certified Gateways
@hvaccontrols
Open source version - http://bacnet.sourceforge.net/
As I see that the download is 1.8MB I think you can implement at most a susbset on an Arduino (maybe an Arduino as a Bacnet device?) but then again don't let my opinion withhold you from proving me wrong 
@Charlie
Do you think its possible to have an Arduino as a BACnet (compatible) device?
BACnet (Building Automation Control network) is an ANSI/ASHRAE standard. The current published version is 135-2008 and there are several published addendum. A good jumping off point for getting information is BACnet.org.
Charlie is correct. BACnet is complicated and can be quite time consuming to implement for anyone who is new to the standard. It certainly takes more than "Googling around". BACnet has been under active development with ASHRAE for over 25 years, and there have been literally tens, if not hundreds of thousands of man hours involved in the development of the 688 page standard that is currently published (ANSI/ASHRAE 135-2008) and the peripheral test standard (135.1-2007).
Our company, PolarSoft, makes several products to aid in the develop of a BACnet product. These products range from Windows DLL to full source stacks written in C. We also provide development services for anyone looking to have experts implement the BACnet protocol in their product and have done so for many, many commercial products (embedded and otherwise).
From my experience, BACnet can be implemented in Arduino (the mini would be a tough choice , but the Mega would provide a little more breathing room), however the biggest problem you're likely to encounter is the amount of available RAM. Normally, each I/O point is represented in BACnet as an object where the type of object is based on the type of I/O. So, if you'd like to represent each I/O as an object then you may run into a RAM constraint. Keep in mind that BACnet has been implemented in assembly in PIC processors, so given the correct design choices it's entirely feasible.
The OP mentioned only implementing BACnet MS/TP, but that's really a red herring. BACnet MS/TP by itself is not really useful in a BACnet device, and by definition isn't a BACnet device at all. MS/TP is the BACnet datalink layer built upon EIA-485 (half-duplex, 3-wire, 9600-115200 baud), and it's a self discovering token ring network. So, a device that ONLY implements MS/TP without a proper BACnet application entity would be meaningless since other BACnet devices would be able to neither discover the device nor read any information from the device.
When someone makes a statement like the OP, (to me) it's like saying "My device has an Ethernet PHY, therefore my device is a web server." There are a BUNCH of implementation details being overloooked.
Having said that, I would certainly encourage the OP to take a look at the open source BACnet project at SourceForge. From that code base, you can pick an choose the portions of the application entity you'd like to implement. I have no association with the open source project, other than I'm good friends with the original author, Steve Karg.
First and foremost, though, if you're going to implement the protocol I'd really encourage you to go get a copy of the standard from ASHRAE. Then, get some of PolarSoft's Windows based test tools to aid in your development effort. 
I've been keeping an eye on the Arduino project for sometime, and have many times considered buying one to tinker with as a BACnet device. If someone can point me in the right direction for the hardware (probably Mega based with a 3 wire EIA-485 half-duplex implementation), then I'd be happy to give it a shot and report the results back here.
I couldn't put links in my first post, so here's a "bibliography" of links.
BACnet.org --> http://www.bacnet.org
PolarSoft --> http://www.polarsoft.biz
Some PolarSoft test programs:
- BACnet Quick Test --> http://www.polarsoft.biz/bqt.html
- BACbeat --> http://www.polarsoft.biz/bacbeat.html
Open Source BACnet Stack --> http://bacnet.sourceforge.net
I looked at BACnet a while back but IIRC you have to pay for the documentation, even a PDF download.
Is that the case?
Rob
Yes, it's currently $119 USD from the ASHRAE bookstore.
$119 USD from the ASHRAE bookstore.
That's the problem, $119 for a PDF, I can't afford that just to see if the protocol is something I'd want to use. 
Rob
thank you all for the answers.
I supposed was not to be easy, in this case would already be done.
What I intend to do is a driver for air conditioning with MSTP.
With the functionality of a thermostat, they can publish some objects.
If the problem is to buy the documents, that's not a problem.
We have experience in LonWorks and do our small development, we are not starting, But in BACNET, yes.
So far we seem to have something clear, we need a mega.
already there to begin more advanced products such as http://bacnetdevelopmentkit.com/, but we want to do it from below.
maybe some other, more open, protocol is more suitable for your project
True.
Rob
I don't have to do anything, I'm not interfacing to a BACnet system or device, I'm just curious about the protocol and - to be honest - possibly would get some ideas to roll my own, which is what I'll do. That's more interesting anyway
Rob
Rob, you could certainly start from the open source BACnet stack, which will get you the datalink layers (including MS/TP) and will act as a starting point for some of the basic services. That's more than enough to allow to experiment with the protocol. And, you don't need to implement it on an Arduino to test it. There are several Windows and Linux based examples that are part of the project.
Hvaccontrols:
What I intend to do is a driver for air conditioning with MSTP.
If you're planning on interfacing with actual HVAC gear via BACnet, especially BTL certified gear, then I would highly recommend a commercial stack. Not that there's anything wrong with the open source stack, but your time to market is going to be much shorter if you go with a commercial stack and customer support.