This post will guide you through setting up SAE J1939 PGN simulation with our JCOM1939 Monitor software, using the Engine Coolant Temperature as a randomly chosen example. It’s important to note that you can configure any PGN with our software. However, it’s crucial to have the SAE J1939-71 Standard (available as a download, currently priced at US$81) as a reference. This standard comprehensively documents all standardized PGNs, their data format, and transmission frequency, making it an essential tool for your setup.
A few notes before we look into the details:
- Our JCOM1939 Monitor software works in combination with one of our SAE J1939 monitor and simulation devices, such as:
- For more detailed information on the JCOM1939 Monitor program, see the online manual.
- It’s important to note that you will need at least a second SAE J1939 node to establish a network. This is a crucial requirement for the setup. If you don’t have access to a second node, consider our SAE J1939 Starter Kit as an alternative.
PGN 65262 Engine Temperature 1
According to the SAE J1939-71 Standard, the Engine Coolant Temperature is part of PGN 65262. It is the first byte in the 8-byte data field defined by SPN 110. SAE J1939-71 also states that the data is transmitted using a one-second interval.
SPN 110 explains the coolant temperature format:
- Length = 1 Byte
- The format is one degree Celsius per bit, with a -40 degree C offset.
- The temperature range is from -40C (-40F – 0x00) to +215C (419F – 0xFF).
SPN 110 – Engine Coolant Temperature Setup
We are using our SAE J1939 ECU Simulator Board with a USB Port in the following. However, the choice of hardware has no impact on the setup process.
As shown in the following image, the device connects per the COM3 port to the software (this is the default but may be different on your computer).
To set up and transmit any PGN, we need to assign a node address to the simulator. You should also set up the device’s NAME, but we use our example’s default settings. Regarding the node address, we’ll go with the default address, 128.
Note: The node address range allows the simulator to find an address other than 128 in case 128 is already taken in the network. If a new address is determined, it will be reported to the JCOM1939 software.
To start the address negotiating process, you must engage the ECU Simulation Mode, as shown in the image, and click the Claim Address command button. The JCOM1939 Monitor program will display the valid node address.
In reference, see the raw CAN Bus data frame for claiming node address 128:
In the Transmit section of the JCOM1939 software, set up PGN 65262, as shown in the image below. In our example, I have set up byte #1 as 0xFF, representing the coolant temperature; the remaining data are set to 0x00 to separate them visibly.
The device will start the data transmission when you click the Save command button. For a reference, see also the raw CAN Bus data:
Engine Coolant Temperature – Simulation
There are two ways of simulating the engine coolant temperature: 1. Editing the data string, or 2. Using a slider as provided by the JCOM1939 software. I chose the slider because it is by far more exciting to use.
In the JCOM1939 software, switch to the Byte Data section, select PGN 65262, and set Start Position to 1 and Length to 1, as shown in the image below. Now move the corresponding slider and watch the data change:
Last but not least, here is the raw CAN Bus data:
Yet again, you can set up any PGN and simulate any data associated with that PGN by using the slider (analog data) or switching to the Bit Data section to simulate digital I/O signals.
SAE J1939 Starter Kit and Network Simulator
Our JCOM.J1939 Starter Kit and Network Simulator is designed to allow the experienced engineer and the beginner to experiment with SAE J1939 data communication without the need to connect to a real-world J1939 network, i.e., a diesel engine. To establish a network, you need at least two nodes. That fact applies especially to CAN/J1939, where the CAN controller will shut down after transmitting data without receiving a response. Therefore, our jCOM.J1939 Starter Kit and Network Simulator consists of two J1939 nodes, namely our jCOM.J1939.USB, an SAE J1939 ECU Simulator Board with USB Port.
The jCOM.J1939.USB gateway board is a high-performance, low-latency vehicle network adapter for SAE J1939 applications. The board supports the full SAE J1939 protocol according to J1939/81 Network Management (Address Claiming) and J1939/21 Transport Protocol (TP).
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