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software simulator for wifi obd2 device

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Intro

sim2.js is modified to be used in terminal environment.

How it works

To start the simulation, open a new ternimal, then type

node sim2.js

It will start a socket server. Address is localhost, port is 35000.

Start another terminal, using the following command to start a socket connection

nc localhost 35000

Try the commands below, e.g., 010D. The return value is 10D61. So the vehicle speed is 61 km/h.

alt text

Try command “ 010C”, the return value is 10C1485, then RPM is 1313.25 rpm.

alt text

Background

Now it is time to send OBD request. Real-time parameters are accessed through Mode 1 (also called “Service $01”), and each parameter has a Parameter ID, or PID for short. All commands can be found in the following page’s Mode 1 list.
https://en.wikipedia.org/wiki/OBD-II_PIDs

For example, we want to know vehicle speed. First search the list for “Vehicle speed”, we found this:
0D 13 1 Vehicle speed 0 255 km/h A

0D is the command to send, since we are using mode 1, the complete command is: “010D”, 13 is decimal conversion of “0D”, 1 is the Data bytes returned, which means we are expecting 1 byte data return.

010D
1 0D FF

We send “010D” and get a response 1 0D FF. Again, 1 is the mode number, 0D is the PID, the last byte FF is the return value. Convert it to decimal value, we get 0xFF = 255 km/h.

Another example, let’s request RPM. first search the mode 1 list for “RPM”, we get
0C 12 2 Engine RPM 0 16,383.75 rpm (256A+B)/4 We notice the command is 12, and it will return 2 bye. The last column is the equation to calculate the final value.

010C
41 0C 0F A0

In the above example, we get A = 0F and B = A0, the final rpm is (256x15 + 160)/4 = 1000 rpm

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