canstm32f4wire
Is the wire used for CAN communication protocol any different or normal. Can normal wires(a pair for CAN LOW AND can HIGH)also be used for communication? I am looking to connect CAN controller 1 to CAN controller 2 in same STM32F407 board.
What kind of wire can be used for this purpose, will any wire be enough?
This 3M cable is available in 7 to 50 twisted pairs. Outer diameter for the 8 pairs is 5.84mm. Available from Digikey, not cheap.
The ends shown seem to be untwisted, which often happens during stripping of the isolation. If you want to be sure the cable has enough twists (about 1 full twist every 5cm is nice), ask a sample from 3M.
Make sure to check the cable's impedance.
1-wire is not a good idea for distances like accross a house. It is inherently single-ended and relatively high impedacne, so quite susceptible to noise. Everything might work fine until the water pump in your furnace kicks in, or you run a particular blender with a failed line filter, etc, etc.
I think CAN makes the most sense. The normal electrical interface for CAN, such as implemented by a MCP2551 and many other chips, is differential. This makes it quite good at noise immunity, certainly much better than 1-wire. At the distance of a normal house, you should be able to run the CAN bus at 500 kHz. That's also way faster than what 1-wire can do, although data rate is probably not a major issue if this network is limited to a few dozen sensors.
The end devices will basically require a micrcontroller each. However, those are small and cheap and low power nowadays. Instead of using bare sensors that talk directly over a 1-wire bus, you have a microcontroller that receives the raw sensor signal. The micro then sends the sensor data on over the CAN bus as defined by your protocol.
One advantage of using micros at each device is that you have much greater flexibility in chosing sensors. You are not limited by the small subset of sensors that have native 1-wire capability. Micros can read the voltage of analog signals, talk IIC, SPI, measure pulse widths, etc. If you have a micro, you can easily make your own sensor. It just needs to put out a voltage and the micro can do whatever interpretation is necessary. For example, making a light sensor would be as simple as tying a CdS cell and a resistor to a A/D input of the micro.
I would put the CAN lines, power, and ground all in one cable. Let that be your "bus". CAT5 cable would be fine for this because it is relatively cheap and readily available. Use one of the four twisted pairs for the CAN lines, and the other three for power/ground. One line of each of these pairs would be power and the other ground, for a total of 3 power wires and 3 ground wires. Get one good efficient DC power supply and have it drive the power for the whole CAN network. I'd probably use 24V DC for the power on the cable. Each device includes a small buck converter to make 5V and/or 3.3V to run the micro, sensors, and whatever other circuitry you might want on a node. Put the power supply near the middle of the bus to minimize the maximum distance from power to any node, and to minimize the maximum power current on any part of the cable.
Best Answer
This depends entirely on the distance between the two controllers and the bit rate you have selected.
CAN is intended to work with twisted pair with a nominal impedance of 120 ohms. However, for lengths with a propagation delay of less than about 10% of the selected bit rate, impedance matching doesn't really matter much.
So for short runs (a few feet) almost any twisted pair will do. Regardless of bit rate and impedance considerations, twisted pair should always be used anyways in order to reduce EMI pickup. And depending on the electrical environment, shielded twisted pair is a really good idea, as well.