TROUBLESHOOTING
The indicator lights are useful in troubleshooting. Unfortunately the Tx and Rx indicators work only when USB
is used.
Step 1: Drivers and supply voltage
Is indicator D1 lit?
•
Yes: go to step 2.
•
No and USB is used: reinstall the drivers.
•
No and USB is not used: check that there is an external power supply connected in J7 or J8. If the power
supply is connected in J8, make sure that jumper J14 is closed.
Step 2: Transmission
Start the application on PC. Examine, if the Tx indicator is blinking. If not, the application is using a wrong
COM port probably. This test is not applicable if USB is not used.
Step 3: Reception
If Tx is blinking but Rx is not, your RS-485 device is not responding. Check that it is powered up, the
connections are correct, and the baud rate and serial address are correct.
Step 4: Bus voltage RS-485
Use a multimeter to measure the voltage between data lines D1 and D0. It should be 0.2 to 5.0 volts, D1
being the positive. If the voltage is 0, the bus is short-circuited or there are no fail-safes.
Measure the voltage at each bus device and pay attention that the polarity is correct (D1 positive).
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