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Help in what way? All nodes will have some sort of controller (ECU) connected to the canbus transceiver.
https://www.instructables.com/A-Simple-Tutorial-for-CANBUS/
CAN in vehicle
- Thread starter Kittu20
- Start date
https://www.instructables.com/A-Simple-Tutorial-for-CANBUS/
The microcontroller node will send CAN messages to switch the lamps on or off.
Maybe the lamps will send CAN messages if the lamps have failed, or maybe the microcontroller will have to request that information.
geekoftheweek
- Joined Oct 6, 2013
- 1,429
Generally speaking in automotive networks everything broadcasts status messages at an interval and everything else reads them and decides if they need to act on them or not. Request type messages are generally only used when a basic status update does not provide enough information like for diagnostics, programming, and certain powertrain functions.
With simple circuits like lights your body controller sends out a status message identifying the status of various switches and your light modules would then decide if it needs to turn on or not. Your light modules would then change the needed bits in it's regularly broadcast status message to reflect if the lights are actually on or off.
Same with the temperature node. It broadcasts a message at an interval stating what the measured temperature is. All the other devices then decide if that message means something to them or not and responds accordingly by turning on or off fans, heaters, and whatever else. The fan / heater / or other controller would then broadcast the status of the devices it is controlling.
The device address is mainly used by the other devices to determine if the message is something they need to act on or not since it is broadcast as the source address.
Although it's not used outside of large trucks, heavy equipment, and "industrial vehicles" the J1939 protocol was designed as a way to standardize communication between products of different manufacturers. There was a time when different manufacturers just used off the shelf parts to build vehicles or equipment instead of producing all the parts themselves or contracting custom parts. If you go far enough back you can line up three or four different trucks from different manufacturers and they will all have the same engines and transmissions in them. It makes a lot of sense when you get into the less accessible parts of the standard (I'm no expert, but I bought a subscription once for a project idea that went nowhere). While it is still used to various degrees there are also proprietary protocols and networks running side by side with it in newer rigs.
From what I can tell when it comes to passenger cars the only standard is the messages that are mandated for emissions testing. Everything else is up to the manufacturer. I have searched and searched online for information, but either it is just not out there, or I needed to scroll through 101 pages of search results instead of 100. With enough time anyone can reverse engineer the basics of how their car works. It is CAN after all and does follow some basic rules.
With simple circuits like lights your body controller sends out a status message identifying the status of various switches and your light modules would then decide if it needs to turn on or not. Your light modules would then change the needed bits in it's regularly broadcast status message to reflect if the lights are actually on or off.
Same with the temperature node. It broadcasts a message at an interval stating what the measured temperature is. All the other devices then decide if that message means something to them or not and responds accordingly by turning on or off fans, heaters, and whatever else. The fan / heater / or other controller would then broadcast the status of the devices it is controlling.
The device address is mainly used by the other devices to determine if the message is something they need to act on or not since it is broadcast as the source address.
Although it's not used outside of large trucks, heavy equipment, and "industrial vehicles" the J1939 protocol was designed as a way to standardize communication between products of different manufacturers. There was a time when different manufacturers just used off the shelf parts to build vehicles or equipment instead of producing all the parts themselves or contracting custom parts. If you go far enough back you can line up three or four different trucks from different manufacturers and they will all have the same engines and transmissions in them. It makes a lot of sense when you get into the less accessible parts of the standard (I'm no expert, but I bought a subscription once for a project idea that went nowhere). While it is still used to various degrees there are also proprietary protocols and networks running side by side with it in newer rigs.
From what I can tell when it comes to passenger cars the only standard is the messages that are mandated for emissions testing. Everything else is up to the manufacturer. I have searched and searched online for information, but either it is just not out there, or I needed to scroll through 101 pages of search results instead of 100. With enough time anyone can reverse engineer the basics of how their car works. It is CAN after all and does follow some basic rules.
