encoder and decoder speed

[young]

I am wondering how fast a HT-640 and HT-680l encoder and decoder can transmitter data correctly. I saw it has applications in wrieless phone, I think it mast be fast, however, when I send data from a pic at high lower than 200ms from the data pin, the data will be missing or do not transmitting data at all, I am curious how it is implemented in wireless phone project, because voice data is huge?

In this case, it is not usable for send many bytes of data, for example, for send 10 bytes of data will cost 2 seconds (according to my current experiment.

please provide some advice!

[young]

and another wired thing is that indoor, the encoder with TWS/RSW434 anneta can send data about 30-50 feet, however out door, it can just send data in 5-6 feet? any suggestion about this why?

[Guest]

Young -

According to the document I have, the Data Rate for the TWS-434 TX module is typically 2.4 Kbps. And for the HT encoder/decoders, for every user bit sent , there are address bits, redundant bits for robustness, etc. This kills the net user data rate because lots of overhead is added to your raw data, but this is the price you pay for reduced error rate. I found that you may even need to send your data (the same data) 2 or more times and do a compare to assure you aren't receiving garbage data.

Much pricier are the Linx modules with external antennas (a wire), but they work over longer distances at higher data rates.

Generally, the successful transmission distance outside is further than in a structure due to less interference outside compared to all the stuff in a building - wires, pipes, walls, etc.

Check out Rentron.com - helpful people for this kind of stuff.

Bill

[Guest]

Thank you Bill:
I tried the system outdoor, it really just worked for a few feet. with encoder and without encoder, I could almost get same result indoor.

I check their datasheet, currently, I did not find more thing that I have done. I will try to dig more into it.

[Guest]

Young -
If you have an oscilloscope, you can check out the maximum hardware data rate of your units without the Holtek encoders/decoders. And you can do it on a benchtop. Hook the scope up to the digital output of the receiver module, which normally goes into the Holtek decoder. Send known pulses (say from your favorite PIC micro) into the transmitter module input, the same pin that would be connected to the encoder output. Send a simple pulse pattern, like 0xAA, so that on the scope you expect to see 1010 1010, where 1 is a high and 0 is a low.

Start with a low baud rate (the width of the 0 and 1 pulses) and be sure what you send is what you receive. If you do this on a benchtop, you can have one scope channel on the Tx data and one channel for the Rx data. Then, increase the data or baud rate - make the sent pulses narrower and narrower - until what you receive starts to get corrupted. This is basically the maximum data rate for the pattern you are sending. You can play with the Rx and Tx board orientations to see how the positions of the antennas affects performance, shield the board with foil to see when the signals get attenuated, etc.

I did this type of stuff with the Lynx modules, not the exact units you are talking about, but the same rules apply. The Linx jobs worked all the way across my backyard, but didn't do nearly as well through walls...

Have fun,
Bill