RS232 by Radio

[Bruce]

almost zero noise

Linx had an LC series, which were incredibly easy to use due to the receivers data output
being very stable in the absence of the RF carrier.

The trade off, of course, was range. They have since dropped the LC series in favor of the
LR (LR stands for Long-range), which now offer 10 times the range of the LC series due to
the increased sensitivity of the newer LR series receiver.

The trade off here is that the newer LR series receivers output random noise. This is what
he's now having to deal with.

If you toss a pair of simple encoder/decoder ICs into the mix, this noise is no longer a factor
since the decoder IC will validate the inbound data several times before changing the logic
on the decoders output.

Ioannis;

What's the sensitivity of your receiver in dBm? If it's anywhere near the Linx LR receivers
sensitivity, we might be interested in stocking your receivers.

[Bruce]

Hi Alain,

The RSSI output is definitely an option, but the difference in overall range has to be
considered. You can use this output for a squelch type circuit, and it's fairly reliable, but
it does have a significant impact on your overall wireless links range.

[Bill Legge]

Ioannis,
I have always thought that Thessalonika (sorry for dodgy spelling) was a wonderful name and was aghast at the ugly industrial developement around the place - how could you do that?

On to things Radio,

It seems to me that the views to date cover:

1. On a good link with high SNR, the SERIN command is OK for most purposes.
2. On a poor link, or at range limits, SERIN (even with 200, Lost_Signal and WAIT("!")) wont work.
3. Some communication systems overcome this by transmitting Data + Some additional bits to check the veracity and, in some case, provide error correction as well. For example CRC, Hamming code and so on.
4. In this case the receiver has to take all the received bits, find the start of frame, apply the checks - and take appropriate action.
5. This sort of complexity is now well known and used.

However, running SERIN2 RxPin, 200, Lost_Signal,[WAIT("!"), My_data] inside a stop-watch timed event would seem a simple and reasonably reliable way to overcome many radio link problems (the '200, Lost_Signal' achieves nothing unless the link is rock solid).

I think I will set up a radio loop and pass data around and run some tests:

1. Change the range to go from good to poor SNR.
2. Change data rates to determine BW issues.
3. Fiddle with the WAIT("XXXXXXXX").
4. Vary the stop-watch time.

And plot all this against error/error rates. I'll come back to you all in 2020 with the results - but I bet all this is already well tabulated somewhere!

Regards Bill Legge

[Ioannis]

What's the sensitivity of your receiver in dBm? If it's anywhere near the Linx LR receivers
sensitivity, we might be interested in stocking your receivers.

The purpose of the modules was to replace the ones I used to get from Aurel or other pin compatible from Asia. I managed to make it cheaper and equally sensitive fore the use onGarage door openrs or other similar short range devices. Freq. is 433.92MHz and sensitivity around -105dBm for 4KHz BW or -109 for 1KHz. Including the SAW filter in the antenna path. Chip used T5744 and on the newer ones TDA5200 with 3db less.

Ioannis,
I have always thought that Thessalonika (sorry for dodgy spelling) was a wonderful name and was aghast at the ugly industrial developement around the place - how could you do that?

Well, I still believe it is one of the best cities for the advatage of combining Sea and Mountain in the reach of your hand. Unfortunately, people deserve the leaders they vote for...

Now on the subject, I think you must give a try to the easier Darrel's Instant Interrupt and when interrupt happens, go there and see if the character was the ! or any other usefull data.

In this case you need the USART of he PIC and the Hserin command. The code will not spend much of the time waiting for the character as Melanie stated, it will be done on the background leaving the main routine to do what is supposed to do.

Ioannis

[Acetronics2]

Hi Alain,

The RSSI output is definitely an option, but the difference in overall range has to be
considered. You can use this output for a squelch type circuit, and it's fairly reliable, but
it does have a significant impact on your overall wireless links range.

Hi, Bruce

I thought RSSI would be a nice info to enter a "strengthened check" routine , so that would not slow down the transmission into the "usable" range ...

Just used as a "Warning" info, if you understand me ...

Alain

[Bruce]

Hi Alain,

I thought RSSI would be a nice info to enter a "strengthened check" routine

You're 100% right. It does.

Ioannis,

Thanks. I'll have to snoop around on your website....;o}