How to achieve long-distance CAN communication

Recently, Mr Huerta, a technology company in Mexico, called for a telephone consultation.

Mr Huerta: “Hello Tony(GCAN), when the CAN communication equipment needs to be transmitted over long distances, how to achieve it? The twisted pair will not work!!!”

GCAN: “What are the devices on your CAN bus, and what is the communication baud rate?”

Mr Huerta: “One master and serveral slave, 250K”

GCAN: “How far do you need to transfer over there?”

Mr Huerta: “The farthest distance between the master and the slave needs to be about 12 km apart, but when the actual test is a few hundred meters, it will not communicate.”

GCAN: “Traditional twisted pair is definitely a certain signal attenuation. If the distance is too far, communication will not be possible. You can convert CAN signal into fiber-optic signal and transmit it with optical fiber. After transmission, it can be transferred back to CAN.” It’s our GCAN-208 series modules.

If you want to learn more about GCAN-208 CAN to Fiber device, Click here

Here, give everyone a simple introduction. CAN-bus uses a differential electrical signal transmitted by the wire. Although the differential signal has strong anti-interference ability, it has a limitation of the transmission distance. Generally speaking, the communication length is related to the baud rate of the bus. When the distance is too long, the signal may be distorted due to environmental problems (such as electromagnetic and electrical interference) and the impedance of the wire itself. The following is the theoretical correspondence between the baud rate and the transmission distance of the CAN bus communication.

As can be seen from the above table, the CAN bus theory has a maximum communication distance of up to 13Km, but under the premise that the baud rate is only 5K, the bandwidth is relatively small and cannot be used in a system with a large amount of data.

The CAN to fiber optic repeater converts the CAN signal into a fiber optic signal and then transmits the signal through the optical fiber. Since the electrical signal is converted into an optical signal, and the propagation speed of the optical signal is much larger than that of the electrical signal, the transmission of the CAN bus data by this method has no limitation of the communication baud rate, and the signal is not present. The problem of interference, the communication distance can be as far as 10~20km, this distance can almost meet the needs of 99% of customers who need long-distance communication.