High-performance SAE J software based protocol stack. Complete J source code is provided. Get on the Bus: J and J Vehicle Bus Standards on established protocols that vary based on vehicle manufacturer, vehicle model. J defines the physical layer, which are the hardware (wiring) and basic protocol that is needed for J and J to transmit messages.

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Starting init included a specific diagnostic connector to be used on all heavy duty vehicles.

I did not get any usefull response on my repeater question. This is a Microchip forum. Thanks to all for your pfotocol. J is a j7108 serial communications bus which is half duplex and multi-master i. It is important to note, that the transceiver should not be used in active mode which is normally used for RS networks.

Omnitracs makes no representations, warranties, or other commitments whatsoever about any non-Omnitracs sites or third-party resources that may be referenced, accessible from, or linked to this site. A message is composed of up to 21 characters, unless the engine is stopped and the vehicle is not moving in which prptocol transmitters are allowed to exceed the 21 byte max message length.

So even if you got past all the problems with the bit stuffing and ACK, there’s no way you could capture all the J data. In the world of electronic data, the bus carries various types of messages formatted to report status, issue commands and request data.

Its main purpose is to address the transmission of electronic signals and information among truck and bus components i. Interfaces are listed by their speed in the roughly ascending order, so the interface at the end of each section should be the fastest. The maximum length, from the MID to the checksum, is 21 bytes. The J device driver was designed by Simma Software and has been used in numerous automotive embedded systems.


The only indication of when the message is over is when the transmission stops. Below is the list of available ports.

j1708 and CAN

Once the bus is idle and the device has waited it corresponding priority based delay time, a device may start transmission. If this time is exceeded, UART based framing errors may occur on the bus.

Why does my PIC32 run slower than expected? J is a multi-master network tooand it implemented the bus arbitration too, but different than the CAN hardware arbitration, J using softrware.

Characters are transmitted in the common 8N1 format.

The last byte of every message is the two’s complement of the MID and data contained in the message. Each subsequent priority adds an additional 0. There are 8 different priorities, ranging from 1 to 8. The first byte of every message is the MID, which stands for message identifier.

J and J Vehicle Bus Standards | Omnitracs

The max length of any J is protocok bytes 10 bits per character. This thread is a little old, but it doesn’t seem like anyone really answered the question, so I’ll give it a try. J Checksum The last byte of every message is the two’s complement of the MID and data contained in the message.

It is designed to work with our J software and abstracts away the technical details and many complexities associated with message timing and interfacing to the physical layer.

Although I can answer some questions about CAN, I am by now means an expert and have only used it for about eight months. If you have questions about J, try our J Introduction.

You can help Wikipedia by rpotocol it. J Physical Layer J uses a twisted pair of wires, with a minimum wire size of gauge. The basic problem is that the CAN specification defines certain requirements around the identifier, or the first part of the message.


However, it is not an RS physical layer, but a closly rembling RS with some modification, any how it is common mode current loop and not a voltage driver.

Technical and de facto standards for wired computer buses. There are numerous CAN forums on the web. View the discussion thread. This technology-related article is a stub. I’m afraid it is “users, help yourselves” here, and unfortunately, not many regular posters are working on CAN. Because of this, it is critical that ECUs guarantee bus access time compliance. When the voltage difference is less than 0. Automotive standards Technology stubs. I only just saw this post. Hallo Thank you for the report back.

We have device drivers for both. J — the physical layer i. Opinions expressed in the content posted here are the personal opinions of the original authors, and do not necessarily reflect those of Omnitracs, LLC or its subsidiaries “Omnitracs”. Retrieved from ” https: This increases the simplicity of your application software, improves your reliability, and shortens your product’s time to market. It is being replaced by J If this were not done properly, then the receiver would flag it as an error.

Transmission is accomplished by controlling the driver enable pin of the transceiver. The reason for this is passive mode allows for non-destructive bus arbitration. Haven’t received registration validation E-mail? Posting images, links and code – workaround for restrictions.