6
AN1176.0
June 20, 2005
position is unused. Default connection is for a shunt to be
placed across the EVI and GND terminals. Note that if V
CC
is used to provide power to remote circuitry, that current
should be limited to less than 50mA to prevent loading the
power switch, shunts, and board traces. The V
BAT
connection should likewise be limited to less than 10mA to
maintain reasonable battery life.
EVENT INPUT, J2
This can be used as a separate input for event detection. If
the connections on J3 are left open, then a normally closed
switch can be connected across J2 for event detection. Pin 1
(square pad) is the input and the other pin is ground.
Troubleshooting
This section will cover commonly-encountered problems in
both hardware and software/USB connections and how to
solve them.
Hardware Troubleshooting
1.
Device doesn’t respond to software commands
Check the V
CC
select shunt on JP1 on motherboard to
make sure it is in place for either 5V or 3.3V V
CC
. Check
shunt on JP1 on daughtercard to make sure its installed
or an ammeter is connected across the terminals.
2.
Device loses time or resets to zero time in backup
mode
Check shunt on JP2 to make sure it is on either
supercap or battery setting. Check to make sure a battery
is installed in BT1 socket if using battery backup power.
3.
Power LED doesn’t light when plugging into USB
cable
This can happen on older PCs that do not have
sufficient USB +5V power or may have had a that power
fail. Try the board on another PC.
4.
Software reads incorrect time when using FREQ
output LED and V
CC
= 3.3V
In this mode it is possible to
get enough noise on the V
CC
line to cause
communications problems with the microcontroller. If
FREQ output testing is done at V
CC
= 3.3V, it may be
necessary to disable the FREQ output when doing other
tests, or use an external pullup of value >10k
Ω
connected
to JP2 of the daughtercard.
5.
ISL1209 board - device shows event is detected
immediately after clearing an event
This indicates the
event switch is open continuously or the event pin is
open. The event pin needs to be held to ground (normally
closed) in order to detect an event.
Software and USB Troubleshooting
Keep in mind that the RTC_USB board uses a serial to USB
converter to communicate, therefore it needs to have a COM
port assigned to it. Many problems can be solved quickly by
noting the COM port number for the PC your are using and
checking the setup menu in the software for that COM port.
Using the Autodetect function in the setup menu will usually
do this automatically for you.
Also note that the serial USB drivers will only work on
WIN98, WIN2000, and EXP machines. WIN NT and earlier
operating systems will not work with the drivers.
1. Software doesn’t communicate with the evaluation
board (Error message “timeout waiting for a
response from device”)
a. First make sure all connections are secure, USB
cable at PC and eval board, and also the
daughtercard connector. If no daughtercard is
connected then there will be an error message. Also
check V
CC
shunts on the motherboard (JP1) and
daughtercard (JP1) are installed.
b. Check COM port used. Although there are 256
possible COM port addresses, the RTC software will
only use the first eight. COM ports 1 and 2 are used
for serial port communications and should be avoided
if the serial port is used. In the FTDI Windows
installation guide and app note, it shows a simple
procedure to change COM ports. Make sure the COM
port selected for the FTDI device is the same as that
selected by the PC. If one COM port is not working,
change to another and try again.
c. The software was opened before the board was
plugged into the USB cable. This will cause setup
problems. Close the software (exit program) and
reopen. If still not working, close software, unplug
board, wait a few seconds, then plug the board in and
open the software.
d. Multiple USB drivers in system. Check the Hardware
Uninstall window (WIN98, WIN2000) and see if there
are multiple serial USB devices shown. Uninstall any
extra ones. Also, check the number of other USB
devices shown. There may be other multiple USB
drivers and some may need to be uninstalled to
resume correct communications.
EVENT INPUT
CONTROL BLOCK
EVENT INPUT
SWITCH
EVENT INPUT
(ALTERNATIVE)
FIGURE 5. ISL1209 DAUGHTERCARD
Application Note 1176
