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Grogster
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Posted: 18 April 2018 at 10:59am | IP Logged Quote Grogster

Chopperp wrote:
Quick Question(s)
Read whole heap of posts on these (HC-12) plus data sheet. Still bit confused.
Do these modules connect to the standard uMite COM 1/COM2 ports or are they SPI or something other?
Secondly, where's a good place to buy them?

Thanks


Hiya.

Yes, they connect via a standard COM port on the MM. This thread is getting a bit more in-depth as to the actual operation of the module itself, and the interface between the MM and the RF chip is handled by the ST MCU on the HC-12, and it talks to the RF chip using SPI, but all the work is done by the ST MCU on the HC-12, meaning that all you have to do, is feed data in(or suck it out) exactly like a wired serial link. They are dead easy to use, and work really well.

They can be had from eBay or Aliexpress for about US$3 or so each. Just search either site for "HC-12" or "HC12" and you should get heaps of hits.

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Azure
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Posted: 18 April 2018 at 11:10am | IP Logged Quote Azure

Grogster wrote:
To confirm this, I could swap the ST chips between the boards. If that is indeed the case, then that would make the NEW one behave if you see what I am getting at.


If it is not too hard to do it would narrow down the cause to the chip or something on the board (you would need to swap both ST's and run both boards to confirm everything follows the ST changeover. ie swapped old board should talk to an unmodified new one and modified new board should talk to unmodified old one.
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Grogster
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Posted: 18 April 2018 at 11:33am | IP Logged Quote Grogster

Yes, that was my thoughts anyway.

Here is a little evidence of what I am saying:

NEW module on Channel 1(433.400MHz):





OLD module on Channel 1(433.400MHz):





Definitely a 30kHz or so frequency problem.


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Chopperp
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Posted: 18 April 2018 at 11:57am | IP Logged Quote Chopperp

Grogster wrote:
Yes, they connect via a standard COM port on the MM. This thread is getting a bit more in-depth...]

Thanks for that. Bit of a bugger when the change things on you. I was a radio tech in my previous life. Many, many frequency measurements made (as well other parameters).
Thought it was a good point to butt in & ask a basic question.
Thanks again

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Posted: 18 April 2018 at 6:17pm | IP Logged Quote CaptainBoing

Grogster wrote:
Yup, the new ones are 37kHz out on the 433MHz band too.

I reset the new module to Channel 1(433.4MHz), and they are NOT there on 433.400MHz on the scanner, but they ARE there on 433.437MHz....



Hmmm... I am wondering if there is something "hooky" about the new modules you have.

The ones I have in stock (with the URL on the silk) match precisely what you show and according to my scanner, 433.4MHz - not as precise as your measurement though.

pix...





Only difference I see is mine have a Philippines version Y of the chip whereas yours are China (?)

I think from what you are showing, they are out of spec with the datasheet - that's enough to go back to the supplier I reckon.


Edited by CaptainBoing on 18 April 2018 at 6:24pm
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Grogster
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Posted: 18 April 2018 at 8:38pm | IP Logged Quote Grogster

Possibly, but I bought these 'New' ones ages ago now - I bought them for stock, as I was always using so many of them at the time. As I had had such great success with them before.....

Technically speaking, if they only list the channel frequencies to one decimal place, then they are still within spec. I am just reading them to three significant figures which is pretty much standard for UHF frequencies, but the old ones are correctly on frequency, so I expected the new ones to be too.

I have a feeling that as far as the producers of the HC12 are concerned, 433.4MHz and 433.437MHz(or so) are the same thing - they only care about 100kHz resolution if you see what I am getting at.

LETS BE VERY CLEAR ABOUT THIS - The new modules work just fine, and do exactly what they say they do, they just seem to have a 30kHz or so error in their channel frequency, which makes them incompatible with the older generation module.

So long as the ones you use, are always the same ones with the same silkscreen, then there should be no problems technically speaking. Weather the channel frequency error then makes the modules 'Illegal' depends on where you place them in the bands you are allowed to use in your country I guess. Taking a very common SRD frequency of 433.92, the closest HC12 channel to this is channel 2 on 433.8MHz. Factor in the 30kHz error, and your actual frequency will be 433.837MHz or so, which is still within 433MHz band for SRD. It's up to the user to be compliant, I guess.

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VK2MCT
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Posted: 18 April 2018 at 10:01pm | IP Logged Quote VK2MCT

Could the 30MHz OSC module be not quite ?

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Posted: 18 April 2018 at 10:32pm | IP Logged Quote Chopperp

On one of the Websites I looked at today, it clearly said that the HC-12 WAS NOT compatible with the HC-11. They had to be used in pairs. NO reason given of course.

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Posted: 19 April 2018 at 7:37am | IP Logged Quote DaveC

issues reported on the Picaxe Forum:

http://www.picaxeforum.co.uk/showthread.php?29875-HC-12-working-supply/page6

and a likely indication of fakes on the HC01 website:

http://www.hc01.shop/productDetail?id=29


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Azure
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Posted: 19 April 2018 at 8:01am | IP Logged Quote Azure

As VK2MCT wrote, it might be worth checking if the XTAL's are a slightly different frequency between the two types of boards.
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Posted: 19 April 2018 at 8:35am | IP Logged Quote Grogster

@ VK2MCT - Yes, I think you are probably right. Especially once I read the couple of posts below your one....

@ DaveC - Thanks very much for that link. This does seem to confirm that there are bloody fakes out there now. Grrrrrrrr......

For this thread's reference, here are the photos that Dave is talking about from the HC12 website:






Apart from the slight silkscreen misalignment on the fakes, they are also easily spotted as fakes by the two extra holes on the PCB, indicated by the arrow. If you have those holes on your HC12's, they are fake ones, so it would seem.

I will now check all the ones I have in stock, and if I find ones without those holes that appear to be genuine, I will then test THOSE - but I fully expect them to be spot on frequency wise, being the genuine article.

Certainly something to be VERY aware of now we know fake HC12's are being sold.

EDIT: The 'Holes' I mention are actually on both. The arrow seems to be indicating the thin silkscreen on the fakes, which shows them up. The genuine ones have a thicker whiter silkscreen. The ones I have certainly seem to be the fake ones based on what I am seeing. Luckily, I have only built about six units with the new 'Fake' HC12's, so I will have to f-ing pull them to bit again, and remove the modules and obtain and install some genuine ones. *sigh* However, looking on the bright side(of life!), I had only built 6 units, not 60 or 600 - that would be an absolute nightmare.

Edited by Grogster on 19 April 2018 at 8:41am


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Posted: 19 April 2018 at 10:42am | IP Logged Quote Grogster

Well, I have checked my stock, and found seven HC-12's which all qualify as being fakes. I have binned the lot.

I bought them as a lot of 15 from AliExpress, but back in November last year, so I can't open any kind of dispute about them now(too much time has passed).

The only thing is, I am trying to remember where I used the other 8 from that batch.....

EDIT: From what I have been able to establish at this stage, after a bit of cross-referencing with the PICAXE thread Dave linked us to, THE GENUINE MODULES HAVE AN OSCILLATOR MARKED AS T300.

THE FAKES HAVE AN OSCILLATOR MARKED AS 30.000MHZ.

Fakes also seem to be about half the price of the genuine ones - US$2.50 or so each, with genuine ones being around US$5 each, so that can be used as a guide.

I was not aware of HC12 fakes existing, so always went for the cheapest ones I could find. Now I know different, I will be more selective in whom I buy them from - but that does not necessarily mean you won't be sold fake ones anyway.

EDIT: I am going to design a small PCB that can be used to test and program HC12 modules. It will used pogo-pins for the HC12, allowing you to plonk one on the board for programming AND testing. This was not really necessary before now, but as there appears to be fakes on the market now, an easy way to test them becomes more important. It can also double as a programmer for them. You will still need a UHF scanner, but hand-held scanner radios can be had very cheaply on eBay etc. Not so good on the transmit side of things, but they work beautifully as a receiver. I will link to one when I have the PCB ready. I will start a new thread for that.

Edited by Grogster on 19 April 2018 at 11:27am


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