Author Topic: FCC Certified Module - Community Recommendations  (Read 563 times)

brolly759

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FCC Certified Module - Community Recommendations
« on: March 29, 2018, 10:55:09 AM »
Hello all, I have been working directly with HopeRF to create an FCC Certified Module. I have made and passed our first v1 module but now I am making my v2 module and would like some community input on what you guys would like to see in it and any recommendations you have.

v1 Module had a Fractus chip antenna, the dimensions was 18 x 24 mm and based off the RFM69HCW but the Signal was not very good using the chip antenna vs wire. Just an FYI, I was told by HopeRF that my duty cycle in FSK mode is TX 30ms every 100ms. Every pin was bonded out using castelation mounting holes.

v2 Module (Estimated size of 18x20 mm)
-u.FL Connector
-ATMEGA328P MCU
-RF69 in High powered mode
-Separate VCC rails for MCU and Radio
-RF Reset pin connected directly to GPIO on MCU

Should I use mounting vias for DIO0 - DIO5  from the radio?

Should I use DIO0 or DIO2 from Radio to MCU INT0 or dont connect it and let the user decide? (PlainRFM69 library uses DIO2 for automode and HopeRF uses it for continuous mode for RF testing)

Should I add a w25x40 on the FCC module to be used for extra space for OTA and UID? Would there be a reason to expose the CS pin for any reason?

Anything else that I am missing or any recommendations from the community?

perky

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Re: FCC Certified Module - Community Recommendations
« Reply #1 on: March 29, 2018, 05:14:17 PM »
I'm not sure what you mean by 'FCC certified'. If you allow the user to be able to change any aspect of the well defined RF performance of the onboard firmware and radio then it cannot be certified, that includes the antenna. Generally certified modules have fixed antenna connections with their own MCU on board that can be proven to meet all the RF requirements, the user cannot alter the code and only interact with it from a higher level often something like an AT style serial interface is used to interface with other equipment. All of this has to be protected so as not to radiate unintentionally or be susceptible to EMI.

Can you tell us what you expect this certification to mean to the user?
Mark.

brolly759

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Re: FCC Certified Module - Community Recommendations
« Reply #2 on: March 29, 2018, 08:29:54 PM »
I am not sure how accurate you are to that. Using U.FL connectors, usually you have guidelines of antenna's tested and what antenna's would be acceptable to use with it. I have seen many FCC certified modules that give you access to the full stack / RF and MCU like the Murata LoRa module and carry its own module certification. I have seen Microchip and xBee lock down their stacks but not everyone does this.

perky

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Re: FCC Certified Module - Community Recommendations
« Reply #3 on: March 30, 2018, 11:18:15 AM »
OK, I was thinking about fully certified module that the user could use 'off the shelf', like the USB modules so got a bit confused. As far as I can see if you were selling a system using a module you would need to get the whole system certified, and in order to fast track the certification of your system you could use a 'pre-certified' radio module. You would need to use exactly the same antenna, modulation technique and timing that the original module was certified with. I also think the end user should not be able to easily modify things (hence the reverse thread antennae that are now in common use!). In reality this means using the same firmware. You still have to certify your final product, but if you're compliant with using the module in that way the process is faster and cheaper.

So it appears pre-certified modules simply show that it would pass given it is used in a very specific way and can speed things up and make the process of certification cheaper. It's risk reduction to getting full certification, the module manufacturer has already shown it can pass, and reduces the risk that firmware that isn't the same but still follows the rules would also pass.

There are rules you need to follow if designing your own module for pre-certification though, such as power regulation on board and using a metal can over the RF stuff.  I found this handy resource. BTW it appears form this that the module has to be stand alone and not part of another system, I read that to mean only a buffered data interface to the outside world and not a control interface to the radio chip. That would appear to mean using an MCU on the module.

https://emcfastpass.com/rf-modules/

Mark.
« Last Edit: March 30, 2018, 11:35:37 AM by perky »

brolly759

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Re: FCC Certified Module - Community Recommendations
« Reply #4 on: March 30, 2018, 11:27:46 AM »
HopeRF is designing the hardware for me, created the metal can, did the impedance matching, etc. I already passed FCC with our first version of the module. I was told that my only rule I need to follow is my TX needs to be no more than 30ms for every 100ms of air time.

perky

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Re: FCC Certified Module - Community Recommendations
« Reply #5 on: March 30, 2018, 11:39:07 AM »
OK, when you say passed FCC, do you mean it actually got an FCC module certificate or do you mean it just passed the FCC tests with a specific system?

Mark.

brolly759

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Re: FCC Certified Module - Community Recommendations
« Reply #6 on: March 30, 2018, 10:31:40 PM »
Passed the FCC Module Cert.

stern0m1

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Re: FCC Certified Module - Community Recommendations
« Reply #7 on: February 02, 2019, 10:50:25 PM »
Is this module with FCC certification available for sale?
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