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The CAN bus transceiver is a key part in many systems, such as cars, factory machines, and embedded devices. It helps different parts of a system talk to each other. If the transceiver does not work well, the whole CAN network may stop working. This article shows how to test the CAN transceiver and find problems step by step.
Common Signs of Failure
When the CAN bus has a problem, the system may stop sending or receiving data. Devices may not respond. The network may slow down or stop. You may not see any signals on an oscilloscope. A CAN analyzer may show many error frames. Sometimes, a device goes into "bus-off" mode.
If you have already checked the software settings and cables, it is a good idea to check the transceiver.
How to Start the Check
First, look at the CAN transceiver chip. If it looks burnt, broken, or has a bump, it may be damaged. Also, check the soldering. If the solder is loose or cracked, the connection may be bad.
Next, use a multimeter to check the power pin. Make sure the chip gets the right voltage, like 5V or 3.3V. Then check the voltage on the CANH and CANL lines. When the bus is idle, both lines should be around 2.5V. If the numbers are much higher or lower, something is wrong. It could be a short circuit, a bad chip, or a missing resistor.
After that, test the termination resistors. Turn off the power. Use a multimeter to measure the resistance between CANH and CANL. If it is about 60 ohms, the resistors are likely correct. If the number is too high or too low, the signal may reflect and cause errors.
Use an Oscilloscope and CAN Analyzer
If the basic checks do not show the problem, you can look at the signal with an oscilloscope. During data transfer, the CANH line should go up to about 3.5V. At the same time, CANL should go down to about 1.5V. The waveform should look like a clear square wave. If there is no change or the waveform is messy, the chip may not drive the bus correctly.
You can also use a USB-CAN analyzer. It can help you see if the device sends or receives data. If you see many errors or no ACK from the device, the transceiver may be the cause. If other devices work fine but one node keeps failing, that node likely has a bad transceiver.
Try Replacing the Chip
If you still cannot find the cause, try replacing the transceiver with a new one. Use the same model. If the CAN bus works after the change, the old chip was bad. If not, the problem may be in the power, wiring, or main controller. In that case, you will need to check other parts of the system.
Summary and Tips
The CAN bus needs both hardware and software to work well. The transceiver is very important. If it has a problem, the whole bus may fail. You can test it with a multimeter, oscilloscope, and CAN analyzer. You can also replace it to confirm the problem.
To make your system more stable, choose good-quality chips like TJA1050 or SN65HVD230. Make sure the bus has the correct resistors and that all nodes share the same ground. Keep wires short and twisted to reduce noise.
FAQ
How do you know if a CAN transceiver is bad?
Signs of a bad CAN transceiver are lost or wrong messages. You might see damage or weird signals on a scope. Errors in communication can also mean it is broken. If you get many errors or no signal at all, the transceiver may be bad.
Can a faulty CAN transceiver be repaired, or should it be replaced?
You usually cannot fix a bad CAN transceiver. It is better to replace it.
