Set Up The CarSim

By using the premade image the car-simulator shall start automatically as soon as the Raspberry Pi has booted.

To configure the Simulator head to the directory:

cd Desktop/carsim/dist/Debug/GNU-Linux/lua_config/

Basics Communication

To simulate a ECU (Electronic Control Unit), the Lua file holds various tables describing the data and behavior. Therefore a single ECU has to provide at least a RequestId and a ResponseId to be able to communicate via the CAN ISO-TP protocol. Note: A single Lua file could contain various ECUs.

PCM = { -- ECU name
    RequestId = 0x100,
    ResponseId = 0x200,
    BroadcastId = 0x300, -- Optional, 0x7DF on default
}

Providing the Simulation Data

To provide a set of response data, there are two possibilities. The first option is to do this via a ReadDataByIdentifier-table, which holds a set of receiving requests and the corresponding answers. The response answer could be a string or a numerical type. The second option is to provide a Raw-table which does basically the same, with the slightly difference, that the entire data is provided as a literal hexadecimal string. This makes it possible to harness data sets from previous scans or logs. However, white-spaces in-between the string bytes are ignored to allow a easier way to separate the data sections.

PCM = {
    RequestId = 0x100,
    ResponseId = 0x200,

    ReadDataByIdentifier = {
        ["F1 90"] = "SALGA2EV9HA298784",
        ["F1 24"] = "HPLA-12345-AB",
        ["1E 23"] = "231132",
    },

    Raw = {
        ["10 02"] = "50 02 00 19 01 F4",
        ["22 FA BC"] = "10 33 11",
    }
}

In the example above, we created a simulator file that now will answer to the given requests. If we for example fire a request to the carsim and with the request id "0x100" and the DID "F190" we will get a response with "SALGA2EV9HA298784".

Integrated Functions

Since it could be a little inconvenient to provide the entire data set in a static, Look-Up-Table styled way, there are also functions to allow a more advanced behavior.

The following functions are available:

• ascii(string) – Converts a UTF-8 string into a lexical hexadecimal byte string
• toByteResponse(number, number) – Converts a int number into a hexadecimal byte string
• getCurrentSession() – Returns the current session
• switchToSession(number) – Sets ECU in the given session
• sleep(number) – Sleeps the amount in milliseconds before proceeding any further
• sendRaw(string) – Sends the given raw-string immediately

All these functions could be used in self defined functions to build a more advanced behavior structure.

Example:

...
    Raw = {
        ["22 F1 91"] = "62 F1 91" .. ascii("SALGA2EV9HA298784"),
        ["19 02 B1"] = function (request)
            myNumber = 21550
            return "59 02 FF E3" .. toByteResponse(myNumber, 3) -- "59 02 FF E3 00 54 2E" 
        end,

        ["19 02 B2"] = function (request)
            session = getCurrentSession()
            return "47 11" .. toByteResponse(session, 1) -- "47 11 01"
        end,

        ["19 02 B3"] = function (request)
            switchToSession(3) -- extended session
            session = getCurrentSession()
            return "47 11" .. toByteResponse(session, 1) -- "47 11 03"
        end,

        ["19 02 AF"] = function (request)
            sendRaw("7F 19 78")           -- send this data section
            sleep(5000)                   -- wait 5 seconds
            return "59 02 FF E3 00 54 2F" -- send the rest
        end
    },
...

In case you know the first bytes of a request, but the following bytes are, for example, a sequence, there is also the possibility to us a wildcard for this request.

...
["05 01 *"] = function(request)
            local answer = "45 01 00";
            return answer;
        end,
...

In this case the Simulator ignores all bytes that are following the 0501 and will always answer with 45 01 00, no matter what appends the defined request. With this possibility you can easily write complex data transfer processes like the simulation of the ECU flashing.