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Forum Index : Microcontroller and PC projects : HC-12 old vs new module....

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Grogster

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Joined: 31/12/2012
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Posted: 05:39am 17 Apr 2018
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I spent most of today, tearing my hair out trying to work out why the hell HC-12's that I have used so many of in the past, would not talk to each other.

If you have two of the older model, they talk fine.
If you have two of the newer model, they talk fine.

If you have one old one and one new one, they DON'T. You will get some messages, but more then 50% of transmissions are ignored by the receiving end. I have no idea why that should be. Triple checked all connections, configuration etc, but if you have one old and one new, they are f-ing hopeless together.

I can configure both with Rob's HC-12 tool, and they both read and write the config just fine, but when you put them online to actually talk to each other, the performance is appalling.

As soon as I put an identical one from my new batch with the thing I was trying to get going(which used the exact same module), it sprung to life with 100% message reliabilty as I have come to expect from the HC-12 modules.

Looking at the modules up close, they appear to be identical electronically, but there is a silkscreen difference with the newer ones over the older ones:







The module with the helical fitted is the OLD one. Note that the newer one has the website on the bottom silkscreen.

The only thing I can think of is that in the newer ones, they have changed something in the code for the on-board MCU, with respect to the way that it talks to the RF chip or something - it makes no sense to me. Has anyone else seen this with their HC-12's?

As I say, not a problem if BOTH(or more) are all the same one, but if you mix them, the results are terrible - even though all the settings are identical.

Smoke makes things work. When the smoke gets out, it stops!
 
Azure

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Joined: 09/11/2017
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Posted: 05:46am 17 Apr 2018
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Just to clarify the setup:

You have a new module with no antenna (helicoil) trying to connect to an old module with an antenna (helicoil).

What antenna configurations have you tried to get them to talk to each other on either/both modules?

 
Grogster

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Posted: 05:55am 17 Apr 2018
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No, both have helicals. I just left the helical on the old one, so you can easily see the difference between the two in the photos.

Here are close-up shots of the MCU's, which do appear to be a different part number:

OLD HC-12 MCU:





NEW HC-12 MCU:




It is possible I am on the wrong track here - I don't really know my ST part numbers, so it might just be an equivalent part.

EDIT: I take that back - they both seem the same. The ST part number would appear to be the 2nd line, not the first one. Both 2nd lines match, so I expect that is the actual MCU part number, meaning both modules are EXACTLY the same.

I need a large Whisky.....Edited by Grogster 2018-04-18
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Azure

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Posted: 06:52am 17 Apr 2018
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This is the chip the bottom right is the date and revision code (page 93 in the manual).

So they are both rev Y of the same chip AFAICT (as far as I can tell).Edited by Azure 2018-04-18
 
CaptainBoing

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Joined: 07/09/2016
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Posted: 07:46am 17 Apr 2018
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Hey Grogs.

How old are those ones without the URL on?

I ask because I just checked, all mine have it and I have used hundreds of the things over the past 3 years with no issues. I can't check those but all the ones I have in stock look like your top image.

This is kind of an earthquake for me and I sympathize with your predicament that you now have a situation where you might add something later that is incompatible... I use these in networks so there is a real possibility (of me adding something that might not work and I never thought to make a record of every one I used... I am even less inclined to arrange time with the customers to do a site survey... gawd!

I know it would be really tedious, but have you tried a mis-matched pair and gradually changing the channel number on one and re-checking each time, just in case they are interpreted differently... I suppose they are all the same band (433MHz)?Edited by CaptainBoing 2018-04-18
 
Grogster

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Posted: 08:24am 17 Apr 2018
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"O Captain, my captain"....

What I might do tomorrow, is hook up both modules(set to same specs), and plonk them on the spectrum analyser and compare outputs. Both are running in same band, yes.
Exactly the same channel. Perhaps there is a frequency difference between the modules, although, I would have seriously doubted it.

The "Old" ones I have are very old. I probably got them from eBay about 8 years ago.
Luckily, I don't have many of those, and all my stock ones have all been the newer type with the website on the bottom silkscreen. I just did not think it mattered, as they were all the same. Or so I thought. Edited by Grogster 2018-04-18
Smoke makes things work. When the smoke gets out, it stops!
 
CaptainBoing

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Posted: 11:02am 17 Apr 2018
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  Grogster said   I just did not think it mattered, as they were all the same. Or so I thought.


Quite... and this follows hot on the heels of me trying to calm a fellow shedders fears about using them "yeah! what you put in one end just pops out the other end, you'll be fine"... I jinxed it really didn't I?
 
Grogster

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Posted: 11:07pm 17 Apr 2018
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Test frequency: Channel 64.(458.6Mhz)

According to my UHF scanner:

NEW type module sitting on 458.637MHz
OLD type module sitting on 458.600MHz

Therefore, NEW one seems to have a 37kHz frequency difference to the older one when set to the same channel.

This is technically now out of licence here in NZ(458.54-458.61 @ 500mW SRD), but would explain why the old and new are not too happy about working together - although set to the same frequency, they are not technically on the same frequency, and if they are a narrow-band transmitter(as I expect they are), then this explains quite a bit as 37kHz off frequency would really stuff things up.

Pain in the arse.

Changing channel frequency won't help, as the channels are 400kHz apart, so moving down to channel 63(458.2MHz as set, but will really be 458.237MHz) is still outside of band too.

I will try a test by resetting the module back to 433MHz band, and see what the frequency error is there. Perhaps it is only in the upper channels or something - which won't help me, but.....
Smoke makes things work. When the smoke gets out, it stops!
 
Grogster

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Posted: 11:43pm 17 Apr 2018
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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....

Configure an OLD one for Channel 1, and it is perfectly on frequency on 433.400MHz on the scanner. I could hook them to the spectrum analyser, but I expect it will tell me exactly the same thing as my UHF scanner is.

Both the old and the new one seem to use the same 30MHz oscillator module from what I can see, so in theory, if the 4461 Transceiver chip uses that as it's reference, then channel 1 should be exactly the same on both. I have downloaded the datasheet for the transceiver chip and am reading some of it now, but agughhhhh.....I don't have time for this.....

Here is a link to the 4461 chip PDF if anyone wants to read it.
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Azure

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Posted: 12:35am 18 Apr 2018
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Had a very quick run through the specs you linked and nothing obvious jumped out.

Do you have a close up of the two chip versions. Might be some chip revision stuff worth looking up.
 
Chopperp

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Joined: 03/01/2018
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Posted: 12:48am 18 Apr 2018
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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
ChopperP
 
Grogster

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Posted: 12:55am 18 Apr 2018
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Both exactly the same part, that being "44631B" on the chip, which is a Si4463 revision 1B, so the RF chips are identical.

Looking at the datasheet, page 33 talks about setting the frequency synth, and so I suspect that in the latest version of the HC12 firmware(in the ST chip on the module), they have changed the stepping factor for setting the frequency, which would explain this issue.

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. Naturally, that is not a practical fix for the issue, but it would prove one way or another if the ST MCU is the problem here, and I now suspect that it is - it HAS to be, cos everything else is identical between the two different boards.
Smoke makes things work. When the smoke gets out, it stops!
 
Grogster

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Posted: 12:59am 18 Apr 2018
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  Chopperp said   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.
Smoke makes things work. When the smoke gets out, it stops!
 
Azure

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Posts: 446
Posted: 01:10am 18 Apr 2018
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  Grogster said  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.
 
Grogster

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Posted: 01:33am 18 Apr 2018
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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.

Smoke makes things work. When the smoke gets out, it stops!
 
Chopperp

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Joined: 03/01/2018
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Posts: 491
Posted: 01:57am 18 Apr 2018
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  Grogster said   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
ChopperP
 
CaptainBoing

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Posted: 08:17am 18 Apr 2018
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  Grogster said   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 2018-04-19
 
Grogster

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Posted: 10:38am 18 Apr 2018
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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.
Smoke makes things work. When the smoke gets out, it stops!
 
VK2MCT
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Joined: 30/03/2012
Location: Australia
Posts: 119
Posted: 12:01pm 18 Apr 2018
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Could the 30MHz OSC module be not quite ?

John B.
 
Chopperp

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Posted: 12:32pm 18 Apr 2018
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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.
ChopperP
 
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