Egnite Ethernut 5.0, Hardware Manual

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Ethernut 5.0 Hardware Manual
Troubleshooting
At some time in the life of your Ethernut may suddenly cease to function. This
may happen due to bad configuration or hardware trouble. This chapter provides
some hints on tracking down the problem.
Before proceeding, remove any hardware attached to the expansion port and
check again the precautions in the chapter "Quick Start".
Basic Checks
If the red LED is not lit, make sure that the mains adapter used for power supply is
working. Some adapters expect a 2.5mm center pin at the barrel connector, while
the one mounted on Ethernut is 2.1mm. This may give an unreliable contact.
If the power supply is working, the fuse may be blown. The fuse is manufactured
by Littelfuse, it's catalog number is 0453.500. The boards are shipped with a
spare fuse. To avoid blowing the next fuse again, move forward to the next
chapter, describing some advanced checks.
Even if the red LED is lit, you should still replace the power supply in the first
place. Some of them have too high ripple voltage, others do not output the voltage
level they claim to do. In rare cases the start-up ramp of the output voltage may
let the board initialization fail.
If you can't get any output from U-Boot, then the problem is most probably with
the RS-232 cable or the terminal emulator. Ensure that the COM port parameters
are set to 115200 baud, no parity, 8 data bits, and 1 stop bit and that all
handshakes are disabled. If all had been configured correctly and if it still fails, try
a different emulator program, replace the cable and finally try another PC.
Advanced Checks
These checks require additional equipment, which may not be available for you or
may require specific knowledge you do not have. If this is the case and if your
board is still showing no signs of life, contact either your distributor or egnite
GmbH directly.
In cases of power supply problems, use a lab power supply with current control.
Replace the fuse on the Ethernut board and carefully increase the voltage, starting
at the minimum. The board should never draw more than 200 mA. Higher currents
must be considered as shortcuts. Several chips are separated from the power
supply plane by ferrite beads. Replacing them one after the other may help to find
the problem.
If the current is within limits, you can check the board's internal voltages.
Expansion port pins 5 to 8 provide the ground level, while 5.0V and 3.3V are
available at pins 3 and 1, respectively. The 1.8V supply can be checked at the test
point near C14.
If the power supply is OK, check that the NRST signal (see schematic page 4) is at
high level.
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