I've heard of On Board Units (OBU) can communicate via RS485.
My question is, how?
For example, I would like to ask the state of some runtime variables from the OBU (what doors are open?, etc.)
Or another example, I would like to send some data to the OBU (outside temperature).
What protocol must I implement to do these? Are the any sample implementations available somewhere?
Thanks,
krisy
Related
I am trying to implement a VANET model for smart parking simulations. Trying to fully understand the TraCIDemo11pp.cc and files relevant to it and its proving quite difficult to get my head around the general structure of each module and the communications between them despite understanding the TicToc tutorial.
I understand how SUMO and OMNETPP are run in parallel, TraCIScenarioManager from OMNETPP communicates with the TraCI server in order to exchange information to SUMO etc. But I'm finding it hard to get my head around how the TraCIDemoApp is utilised.
The question is quite specific, but hoping an answer to it would let me figure out the rest. Any help would be appreciated!
Thanks,
Wesley
Veins comes with a very small demo example in the city of Erlangen:
Vehicles start at the parking lot of the university and drive to a location off-sight. After some time the first vehicle (node[0]) emulates an accident and stops driving. Therefore, it broadcasts this information which gets re-distributed via the RSU to all other vehicles in range. They, in turn, try to use an alternative route to their destination while re-broadcasting the information about the accident. Thus, newly spawned vehicles also get informed and immediately try to choose a different route to the destination.
All of this (i.e. accident, broadcasting, switching route) is implemented in the TraCIDemo* files which represent a VANET application running in a car or RSU utilizing the NIC (i.e. PHY & MAC) to do communication. See what policy is based vehicle rerouting in case of accident? for more information.
handleParkingUpdate() is used to react to a vehicle having switched it's state from driving to parking or vice versa. Depending on the current state and whether parked cars should be allowed to communicate in the simulation this method registers the vehicle's NIC module at the BaseConnectionManager which is involved in handling the actual wireless communication. For more details see this module or follow a packet from one application layer to another (i.e. twice through the networking stack and the wireless transmission).
I am using a Cyclone V on a SoCKit board (link here) (provided by Terasic), connecting an HSMC-NET daughter card (link here) to it in order to create a system that can communicate using Ethernet while communication that is both transmitted and received goes through the FPGA - The problem is, I am having a really, really hard time getting this system to work using Altera's Triple Speed Ethernet core.
I am using Qsys to construct the system that contains the Triple Speed Ethernet core, instantiating it inside a VHDL wrapper that also contains an instantiation of a packet generator module, connected directly to the transmit Avalon-ST sink port of the TSE core and controlled through an Avalon-MM slave interface connected to a JTAG to Avalon Master bridge core which has it's master port exported to the VHDL wrapper as well.
Then, using System Console, I am configuring the Triple Speed Ethernet core as described in the core's user guide (link here) at section 5-26 (Register Initialization) and instruct the packet generator module (also using System Console) to start and generate Ethernet packets into the TSE core's transmit Avalon-ST sink interface ports.
Although having everything configured exactly as described in the core's user guide (linked above) I cannot get it to output anything on the MII/GMII output interfaces, neither get any of the statistics counters to increase or even change - clearly, I am doing something wrong, or missing something, but I just can't find out what exactly it is.
Can any one please, please help me with this?
Thanks ahead,
Itamar
Starting the basic checks,
Have you simulated it? It's not clear to me if you are just simulating or synthesizing.
If you haven't simulated, you really should. If it's not working in SIM, why would it ever work in real life.
Make sure you are using the QIP file to synthesize the design. It will automatically include your auto generated SDC constraints. You will still need to add your own PIN constraints, more on that later.
The TSE is fairly old and reliable, so the obvious first things to check are Clock, Reset, Power and Pins.
a.) Power is usually less of problem on devkits if you have already run the demo that came with the kit.
b.) Pins can cause a whole slew of issues if they are not mapped right on this core. I'll assume you are leveraging something from Terasic. It should define a pin for reset, input clock and signal standards. Alot of times, this goes in the .qsf file, and you also reference the QIP file (mentioned above) in here too.
c.) Clock & Reset is a more likely culprit in my mind. No activity on the interface is kind of clue. One way to check, is to route your clocks to spare pins and o-scope them and insure they are what you think they are. Similarly, if you may want to bring out your reset to a pin and check it. MAKE SURE YOU KNOW THE POLARITY and you haven't been using ~reset in some places and non-inverted reset in others.
Reconfig block. Some Altera chips and certain versions of Quartus require you to use a reconfig block to configure the XCVR. This doesn't seem like your issue to me because you say the GMII is flat lined.
I have a Keyspan PCI to RS-422 adapter that I'm using to connect old serial devices to a Macintosh. I would like to use NSInputStream and NSOutputStream to read and write so that I can take advantage of asynchronous nonblocking I/O since there will be several devices attached to this system that each have their own idiosyncrasies.
My question is how can I access some low level parameters for the devices using a NSStream (baud rate, count of stop bits, parity, etc)?
I thought I researched everything before I asked the question, but the answer was in another class (NSFilehandle).
I'm looking for some input on witch file transfer protocol to use over a serial line. I want to be able to transfer files of max 200 Mb size over a serial line (RS232) in both directions, but only one of the machines needs to be able to initiate the get/put (think master-slave).
The protocol also needs to be:
Easy/simple to implement since I would need to write both client and server myself (limited, embedded hardware)
Fairly robust, fault checking/recovery etc
At least somewhat standardized, in case I need to get a third party to implement it on some other hardware
Kermit? TFTP? Simplest possible home brew? What do you think?
In the beginning was the Xmodem, which was very simple to implement. Chuck Forsberg looked at the xmodem and decided it was inefficient, so he begat the Ymodem, but it's implementations were buggy and both x and ymodem were replaced with Zmodem.
Kermit followed on later. Kermit would probably be the "Standard" way to implement this. Do you have access to libraries for Kermit that will run on your embedded platform? If not I would probably consider one of the other options.
If ease of implementation is your primary concern then Xmodem wins hands down.
I've been reading about TDD, and would like to use it for my next project, but I'm not sure how to structure my classes with this new paradigm. The language I'd like to use is Java, although the problem is not really language-specific.
The Project
I have a few pieces of hardware that come with a ASCII-over-RS232 interface. I can issue simple commands, and get simple responses, and control them as if from their front panels. Each one has a slightly different syntax and very different sets of commands. My goal is to create an abstraction/interface so I can control them all through a GUI and/or remote procedure calls.
The Problem
I believe the first step is to create an abstract class (I'm bad at names, how about 'Communicator'?) to implement all the stuff like Serial I/O, and then create a subclass for each device. I'm sure it will be a little more complicated than that, but that's the core of the application in my mind.
Now, for unit tests, I don't think I really need the actual hardware or a serial connection. What I'd like to do is hand my Communicators an InputStream and OutputStream (or Reader and Writer) that could be from a serial port, file, stdin/stdout, piped from a test function, whatever. So, would I just have the Communicator constructor take those as inputs? If so, it would be easy to put the responsibility of setting it all up on the testing framework, but for the real thing, who makes the actual connection? A separate constructor? The function calling the constructor again? A separate class who's job it is to 'connect' the Communicator to the correct I/O streams?
Edit
I was about to rewrite the problem section in order to get answers to the question I thought I was asking, but I think I figured it out. I had (correctly?) identified two different functional areas.
1) Dealing with the serial port
2) Communicating with the device (understanding its output & generating commands)
A few months ago, I would have combined it all into one class. My first idea towards breaking away from this was to pass just the IO streams to the class that understands the device, and I couldn't figure out who would then be responsible for creating the streams.
Having done more research on inversion of control, I think I have an answer. Have a separate interface and class that solve problem #1 and pass it to the constructor of the class(es?) that solve problem #2. That way, it's easy to test both separately. #1 by connecting to the actual hardware and allowing the test framework to do different things. #2 can be tested by being given a mock of #1.
Does this sound reasonable? Do I need to share more information?
With TDD, you should let your design emerge, start small, with baby steps and grow your classes test by test, little by little.
CLARIFIED: Start with a concrete class, to send one command, unit test it with a mock or a stub. When it will work enough (perhaps not with all options), test it against your real device, once, to validate your mock/stub/simulator.
Once the class for the first command is operational, start implementing a second command, the same way: first again your mock/stub, then once against the device for validation. Now if you're seeing similarities between your two classes, you can refactor to your abstract class based design - or to something different.
Sorry for being a little Linux centric ..
My favorite way of simulating gadgets is to write character device drivers that simulate their behavior. This also gives you fun abilities, like providing an ioctl() interface that makes the simulated device behave abnormally.
At that point .. from testing to real world, it only matters which device(s) you actually open, read and write.
It should not be too hard to mimic the behavior of your gadgets .. it sounds like they take very basic instructions and return very basic responses. Again, a simple ioctl() could tell the simulated device that its time to misbehave, so you can ensure that your code is handling such events adequately. For instance, fail intentionally on every n'th instruction, where n is randomly selected upon the call to ioctl().
After seeing your edits I think you are heading in exactly the right direction. TDD tends to drive you towards a design composed of small classes with a well-defined responsibility. I would also echo tinkertim's advice - a device simulator which you can control and "provoke" into behaving in different ways is invaluable for testing.