Q1. Can I connect PLM-24 to a RS-232C serial port?
Yes, but since the voltage levels on the RS-232C serial port is ± 12V you have to use an interface circuit like
MAX232 or similar (PLM-24 uses standard TTL/CMOS levels). Schema is included in the manual.
Q2. Do I need any special or expensive development tools?
No. You can use the tools you already use for writing programs to your MCU or PC as long as it's able to
send and receive serial data at 2400 bps or less.
Q3. Do I have to use a protocol?
No, you don't have to but we recommend you implement some way to find out if the data sent was received
by the receiver and contains valid data. There is many ways to do this and our tip is to start simple and go
from there. See S.N.A.P for
information about an easy to learn protocol.
Q4. Where can I read more about different protocols?
There are lots of books available that describes different protocols. Go to your library and borrow a book
about TCP/IP, IPX, AX-25 or another general network protocol to get an idea what a protocol is all about.
Also do a search on Internet about CRC and checksum and you will probably get lots of links with valuable
information.
Also take a look S.N.A.P. It's a open and
free network protocol primary intended for PLM-24 based
home automation networks.
Q5. I get poor results when sending at 2400 bps, is something wrong?
Not necessary, first of all you can try to tune the core in TR1 and see if that helps. If you experience periods
during the day when the communication is poor it may be that something in your house/building is generating
noise on the power line (or blocking your signal) se Q&A number 9.
Q6. How many PLM-24 units can I have?
Since PLM-24 is protocol independent it is up to you. You can have as few as two up to several thousands
if you need that. You decide this yourself by the address handling in your program.
Q7. How far does the signal goes?
It's a tricky question to answer but PLM-24 is intended to be used within a house/building and the signal
will not pass trough a distribution transformer that may exist between houses or blocks. Sending data over
longer distance may force you to decrease the transmitting speed. The distance you can communicate is a
factor of characteristics of your wire, loading and noise.
Q8. Can I use my existing X-10 equipment?
Yes, you can still use all your existing X-10 equipment and PLM-24 will not false trigger any of
the X-10 units. You can also download source code and schematics for an PLM-24 to X-10 Gateway.
Q9. Communication becomes poor when i plug-in brand X in the outlet?
Some appliances such as particular brands of televisions or other audio/visual equipment may have a
capacitor across the AC line to filter out high frequency noise. PLM-24 signals appear as high frequency
noise to these capacitors and are thus attenuated.
Also some power strips that have filters in them to protect electronic equipment effectively filter out
PLM-24 signals. Cheaper power strips that protect against voltage spikes only do not affect this signals.
Try moving the PLM-24 module from power strips to a standard outlet if they don't seem to be working.
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