HT12A/HT12D Usage Questions

[Dotnet]

Hi All

I was hoping someone could hepl clarify the usage and operating characteristics of the above devices - have downloaded data sheets from Holtek not the most helpfull in thw world!!!!

I am designing a small project which requires 4-bit decodable data to be transmitted via one of the ubiqitous UK License Exempt AM/FM RF beasties - obvously for the encoding half the HT12A jumps out, (and for the decoding half the HT12D)

OK Question 1, CAN the HT12A be used with RF (instead of IR in the datasheet) if so what is the configuration for the carrier OSC inputs (or lack of!!)

2nd Question, in a typical pairing of the above devices can a steady logic output be obtained at one of the data outputs of the HT12D (obviously with a bit of logic) if one of the Tx buttons is HELD down. I am presuming the ouput will pulse for a brief key press.

Thank in advance
Dotnet

 

[zachtheterrible]

Question 1: I was going to use the HT12A, but hten I realized that I could use the HT12E to do the same exact thing, but with less components, and all around much easier.

Question 2: Yes, if you hold it down, you will get a continous logic output.

Save yourself the trouble and just use HT12E.

 

[Dotnet]

Dotnet Reply

HI Zachtheterrible,

Thanks for the reply.

If my understanding (and from the datasheets) is correct - how?
The HT12E utilises all 12 I/O lines as addresses i.e to verify the validity of data then sends the VT line high whereas the HT12A has the ability to both send data and to validate the Tx originator.

I need 3 separate on / off 'lines' (momentarily pulsed) and one effectively mirroring the length of time a switch is held down (for a motor control - direction immaterial)

Do I still have to use a resonator if I am going to use RF?

P.S. I agree with the reduced component count but I dont see any other way

Dotnet

 

[zachtheterrible]

Hi dotnet, no need to post a mesage saying you need help on this one. This thread was very close to the top of the list.

Anyway, HA! you sound just like me. Thats exactly what I orignially thought that it was all address pins, but if you look at the datasheet, it says AD8 - AD11. This stands for address data port. I don't know why they call it an address :roll: . I came under criticism for this, but now I know that the datasheet was indeed misleading

It will work just like you are explaining: You can have four seperate pins go high and low on the HT12D by pressing the four pins on the HT12E.

Keep in mind that the TE pin must be activated in order for the HT12E to do anything. Do just like the datasheet says with the four diodes, otherwise if you activate one AD port, all of them will get activated. :lol:

 

[Dotnet]

Hi zachtheterrible,

Sorry abot the re-thread some NGs are quite anal when it comes to replied threads. If there IS a reply they deem it answered or closed and not bother rvieweing the question - I'm new to this site still learning it's etiquet.

You're quite right it does say ADx saw it - read it- didn't 'see' it.

If I'm interpreting the waveforms correctly I presume there is not a problem with 'switch bounce' and then the associated transmit signal i.e. I don't need a slight delay between the switch closing and the TE signal getting pulsed.

Last question (I promise)
As mentioned previously, I want the decoded outputs 'mirror' with 3 on/off inputs and one duration type output, will the L/MB pin on the 12A cause any issues in the regard?

Oh! why did you 'come under criticism'

Thanks
Matt

 

[zachtheterrible]

Hi dotnet, I don't have to use any kind of switch debouncing

Last question (I promise)
As mentioned previously, I want the decoded outputs 'mirror' with 3 on/off inputs and one duration type output, will the L/MB pin on the 12A cause any issues in the regard?

Could you explain this a little more? I don't get what you mean.

 

[Gary2010]

Hey guys i got a similar problem to the one mentioned above, im a novice in the electronic world so to speak, n this is my first project on a wireless topic.

i tried connecting the dout pin of the ht12e to the din of the ht12d to check the encoder decoder ics, but the data doesn't seem to be sent across,
i even kept the TE pin low(as it is active low)
help me out pls