HT-12E encoder question

There is four input in HT-12E, can I only use one input and ignore other three inputs to input a 10bits serial digital data from ADC?

Thank you very much.

Reply to
sommes
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I think you need to read the data sheet.

Just in case here it is:

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This device take 12 parallel bits and converts them to a serial data stream.

Thats all.

You still need some sort of transmitter.

From the first page "General Description":

" The programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal."

SO you need to provide the "transmission medium". You also need to provide a "trigger signal" (TE)

When the TE signal is low, the HT-12E will transmit the 12 bits over and over again till TE goes high.

I do not think this device will you what you expect.

By the way, what is it you are trying to do ???

donald

Reply to
Donald

Yes, you could do this, but how are you going to reassemble the bits on the other end? What happens if a packet is duplicated or dropped?

This chip is really designed as a four button remote control, so you are using it in a way it was not intended, which is often a problem.

You might get it to work with a parallel ADC, sending all 10 bits at a time. This way, each packet would contain the entire 10 bits. But you would only have 2 bits left for addressing.

Alan Nishioka

Reply to
Alan Nishioka

Thank you Donald, Alan

Thank you for your reply. I am going to list what I try to do.

1) Input 0 to 5V to Atmel AVR AT90S8535

2) 10bit ADC conversion by 8535

3) Encode with HT-12E and transmit by TLP-343

4) Recieve by RLP-343 and Decode with HT-12D

5) Display infomation by 7 Segment display.

I would lik to ask.

Q1) Can Atmel 8535 do the 10bit ADC and output data from RS-232(serial output)?

Q2) Do I need encode HT-12E if serial data is achieved?

Q3) Can I just input the serial data from ADC to TLP-343 transmitter?

Reply to
sommes

transmitter should be TLP-434 reciever should be RLP-434

Reply to
sommes

Probably

Probably not. It does seem silly to convert to parallel then back to serial.

Probably.

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used an avr directly connected to tlp434a for his project.

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would not let me download datasheets.

Alan Nishioka

Reply to
Alan Nishioka

Ok

OK

Why ?

Connect the TLP-343 to a port bit and create a 10 bit serial data stream.

Again why the HT-12D ?

Output of RLP-3433 into port bit of another 8535.

8535 can do this as well.

Yes

NO

Yes

Alan, nice link.

To get ideas for transmit/receive encoded data, google for "manchaster coding".

All this sounds like it will be a lot of work. ( well, for the first time it will be).

There are a lot of projects out on the net to help you along.

Good Luck

donald

Reply to
Donald

Thank you Donald and Alan again.

Can I ask you one more question?

I am using HT-12E, becuase my industry partner told me the encoder is doing some kind of encoding which enable to get rid of noise and the reciever could recieve the encoded data correctly, therefore my partner suggest me to use HT-12E and using the 4 bits input from the chip to send 10bits with 3 cycles(4 bit for one cycle).

Please correct me if it was wrong.

Reply to
sommes

I am sorry, but this does not make any sense.

But, if thats what the client wants......

donald

PS: noise is what the "manchaster encoding" will help with.

Reply to
Donald

The HT-12E encodes a 1 as a short pulse and a 0 as a long pulse. This allows clock recovery at the receiving end. But there is nothing special about this code that gives it better noise immunity. That would depend on what is built into the decoder.

And any kind of coding/decoding could be done in the AVR. But you would also have to do any decoding for noise immuity on your own too.

I still don't see how you will be able to tell where the beginning of an ADC data word is using this method. If you want to use the HT-12E, I still suggest sending 10 bits in parallel in a single packet.

Alan Nishioka

Reply to
Alan Nishioka

Hello Alan,

I think we agree that the HT-12E is not needed in this application.

But, I am confused about "sending 10 bits in parallel in a single packet".

Sending 10 bits in a Manchester Encoding scheme would give a self-clocking data stream.

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donald

PS: Now its up to the OP to decide how much work he wants to do. I think the amount of work to get the HT-12E working is much more difficult. So I hope the OP is charging by the hour. ;-)

Reply to
Donald

I finally read the HT12D datasheet to see what it does for noise immunity. The HT12E sends the same address/data four times in a row. The HT12D compares the four transmissions to see if they are all the same.

Also, my suggestion of sending 10bits at a time won't work because it compares the address bits.

I think it would be easier to use the AVR to do any encoding / decoding / noise immunity.

Alan Nishioka

Reply to
Alan Nishioka

Yes.

The receiver needs to know where the MSB of the ADC data is. I was trying to use the address bits on the HT-12E to send more data (the whole 10bit word in one burst). I did not realize that the decoder treated these address bits specially, so this won't work.

Yes, that would be good to get the bits across, but that doesn't tell you where the MSB is. I believe the project I referenced earlier just used RS232 signaling, which should work and give you the MSB too.

I agree.

Perhaps we should be charging him! :-)

Alan Nishioka

Reply to
Alan Nishioka

:-):-):-):-)

Reply to
Donald

Thank you Alan and Donald again, I really learnt a lot from you guys...By the way.

I will talk to my partner but it is little bit hard to change his mind. It is becuase he think

1) Using HT-12E and HT-12D could get rid of noise, and data can send correctly

2) I can output 10bits ADC serials data to1 of the 4 input from HT-12E to send the data easily, however it would be very slow to do in this way, therefore, my partner suggest me to use all 4 input from HT-12E to send at same time.

What is the best solution to radio transmission 10bit ADC data from Atmel AT90S8535?

Sorry for my bad knowledge of RF

Reply to
sommes

Looking at the data sheet from Laipac for the transmitter and receiver, you _should_ be able to hook up asynchronous serial output from the micro to input pin of the transmitter, and see more or less the same signal on the receiver pin of the matching receiver. You'll have to take the 10 bit number and split it up -- the easiest thing to do might be to just send two bytes, wait a while, then send the next reading, etc.

Better would be to send it with a checksum of some sort because with radio you're practically guaranteed bad data at some point. If I just wanted to send one channel of analog data I'd probably have a five-byte packet: an unambiguous header (0x55?), two data bytes, then a CRC16 checksum. If you don't want to do CRC16 and don't mind a greater chance of error you could use CRC8, or even a sum-of-bytes, but a CRC would be significantly better.

The next time you ask one of these questions you may get better response if you:

  • say what you're doing beyond just sending data
  • include pertinent details, like data rates and frequencies
  • tell us what you _do_ know
  • don't assume that we know what company's products you're using
  • don't assume we know everything about that company's products
  • don't assume that we want to go read their website

Something like "I want to send data at 4800 baud on a 434MHz data link. I'm going to use an Laipac HT-whatever plus a TRX-whatever else, and I need to know how to make it all work."

--
Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

If noise is seriously considered a problem would it be worth trading off some throughput speed by using all four of the inputs for one-bit data, with two bits inverted and two bits non-inverted. Check at the receiver to derive a confidence bit.

Ken

Reply to
Ken Taylor

Some how I do not think thats the real problem.

Is it that, he thinks a tiny piece of cheap hardware is better than 4 weeks of software development ?

After the software is developed, there are no HT chips at all.

Silly, but doable. Just takes time.

Its been stated several times already.

One bit out to Tx, one bit in from Rx.

This is has not been an RF problem, its a software problem.

How much software ( in other words, how much will it cost ) do you eant to develop ?

Show your partner these posts. Tell him it will be cheaper with the software method.

donnald

Let us know what you end up doing.

Reply to
Donald

I have done this with a PIC, not an Atmel chip, on the PIC serial interface you have the option of sending a 9 bit byte instead of the usual 8. So you can use that extra bit as a way to code whether the byte you are sending is the high or low byte of your 2 byte data sample. It's not as good as sending in frames and doing proper checksums, but it's a simple way to send 10-16 bit data over a radio link, you can check at the receiver that you are getting pairs of bytes, generate an error if not, discard some data and then resynchronise. I have no idea if the Atmel chip can also do this in it's hardware, maybe not, though if you write your own serial output code to drive a pin on the Atmel then you could implement this method.

Steve

Reply to
Steve

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