Probe your serial PIN at the end of the transmission. If this pin is HIGH, you're in the TRUE mode, unless you're in INVERTED mode.
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Probe your serial PIN at the end of the transmission. If this pin is HIGH, you're in the TRUE mode, unless you're in INVERTED mode.
Steve
It's not a bug, it's a random feature.
There's no problem, only learning opportunities.
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Have ordered a couple of linx TXM-418-LR modules - hopefully they will work better for my application - anyone had success with these? They actually look like really good bit's of kit, cheap, small and overpowered! The only downside to prototyping with them is they r SMD.
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George, I recently purchased a 2 pair of LINX RXM-433-LR-S and TXM-433-LR-S modules from parallax. They come with antennas and have interface circuitry for level shifting to 5 volt levels. I have used them with manchester coding and a sync pulse and have gotten distances of a few hundred feet. However the baud rate is quite slow as they tend to delay the received signal above about 2 milliseconds per bit. I am currently running them at about 500 baud manchester. Much above and they are unreliable. Don't beleive the claims of 10k baud..... However if you are set on purchasing them I would get them from Parallax, as I said they are fully assembled and ready to be pluged into your circuit. Best of luck....
Dave Purola,
George, Here is the link....
http://www.parallax.com/detail.asp?product_id=28180
Last edited by Dave; - 27th February 2007 at 01:58.
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I've got a pair of those on a temp sensor/logger/thingy out inside my garage. Distance from garage to house is about 275ft, TX inside garage, RX inside house. I'm running 19.2K w/ manchester coding (9600 baud effective rate). And they work great, not using anything for error detection or correction...Originally Posted by Dave
But as the site says, the range is 'based on environmental conditions', 'your mileage may vary', 'do not take with alcoholic beverages', 'the check is in the mail', 'see a doctor before using', etc...
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skimask, I bet your sending data continously. As I ran these tx/rx modules on the bench I noticed that the more data they sent continously the better the receiver alligned to the transmitted signal. I send 1 packet of 32 bits (64 manchester bits) with a sync pulse once every minute and the best reliable baudrate I can get is 500 baud manchester. I suppose if I sent a couple thousand bits I might pick up 1 or more packets at 380 ft.. Are you using the stock antennas or have an external antenna?
Dave Purola,
N8NTA
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Stock antenna's that came with the modules (the little whips), not really placed up high or anything, eye level on the TX, waist level on the RX. Not continuous data, however, I 'preload' the TX with a decent amount of sync (64 x $AA, I read somewhere once that these types of TX's want about 5ms of preamble before they really work well), then 2 $55's, then send the temp data word, repeated 4 times.
The RX won't take the data unless it first sees 32 x $AA, then the 2 $55's, and it really won't take the new data unless it sees 3 out of the 4 data words equal each other. I set it up so the TX PIC only wakes up once a minute and it only sends data if the temperature changes more than 1 degree F. The RX has an RTC on it and keeps track of time (incidentally, the RX also powers down for 55 seconds after receiving the data because I know it'll never get another packet before that, every last bit of power at both ends, even though the RX is wall-powered).
And for the physical impediments to RF transmission:
TX antenna -> concrete block wall -> open air for 275ft (give or take 10ft) -> house siding -> stud wall with insulation -> sheet rock wall x2 -> RX antenna.
But that's just my happy story my good transmission. I suppose if I would've got the next module down the manufacturing line, I could just as easily be running 1200 baud for 50ft at most.
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Sounds hopeful anyrate, I had a look at the paralax website and am wondering what the other components on the board do - the Linx website say there r no external components required and show schematics of it hooked directly to a PIC - any ideas?
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I use the Linx LR series in a ton of various applications, and have no problem at all with 9600bps up to 2000'.
If you're using the Parallax modules, your range may be limited by the antennas they use on the modules.
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