Does custom firmware invalidate FCC modular approval?

RE: Does custom firmware invalidate FCC modular approval?

Susheel Nuguru — Tue, 12 Dec 2023 12:25:11 GMT

Thanks for your contributions ecorm.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Tue, 12 Dec 2023 10:29:31 GMT

I've done some more digging, and it appears that NRF_GZLL_DATARATE_1MBIT_BLE and NRF_GZLL_DATARATE_2MBIT_BLE can be passed to the nrf_gzll_init function. The fact that Gazell can be configured to use the same modulation modes as the BLE SoftDevice gives me more optimism that an FCC "Permissive Change Class 1" can apply if I reflash a certified module to use Gazell. In particular, I was worried about the 6db bandwidth requirements of FCC 15.247 (a)(2).

I'm posting my findings here in case it helps others in the same predicament as I. I hope this is okay.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Tue, 12 Dec 2023 05:13:09 GMT

I was considering the "Permissive Change Class 1" route, but as the Gazell and BLE stacks seem to be closed-source (understandably), I am not sure if this is easily demonstrable.

The 178919 D01 Permissive Change Policy v06 document has some guidance on permissive changes.

Assuming that Gazell uses the proprietary Nrf_2Mbit RADIO mode (as opposed to Ble_2Mbit mode), that is yet another complication in pursuing the FCC permissive change route.

It would be way simpler for me if a third-party module vendor were to certify their module using the Gazell protocol. Either that, or I pay Bluetooth SIG their exorbitant fees, including a lawyer to interpret all their terms and conditions.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Tue, 12 Dec 2023 01:36:31 GMT

[quote userid="130365" url="~/f/nordic-q-a/106449/does-custom-firmware-invalidate-fcc-modular-approval/459806"]As a bonus, they have nRF-based modules which use a proprietary protocol.[/quote]

I checked, and their proprietary protocol is fixed-channel and does not feature frequency hopping like in Gazell.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Tue, 12 Dec 2023 01:05:04 GMT

I have just stumbled upon this App Note from Wurth Elektronik that explains things better than anything I have found so far:

ANR031 - Certification of custom modules

https://www.we-online.com/components/media/o705723v410%20ANR031_CertificationCustomModule.pdf

As a bonus, they have nRF-based modules which use a proprietary protocol. I'll check them out to confirm they are royalty-free and appropriate for my application. Note: I am not affiliated with Wurth Elektronik in any way, and I'm not even an existing customer.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Mon, 11 Dec 2023 19:34:45 GMT

[quote userid="6207" url="~/f/nordic-q-a/106449/does-custom-firmware-invalidate-fcc-modular-approval/459671"]Any application accessing the RADIO features though our qualified protocol only though the certified module hardware[/quote]

Is Gazell a "qualified protocol" that's been certified?

[quote userid="6207" url="~/f/nordic-q-a/106449/does-custom-firmware-invalidate-fcc-modular-approval/459671"]but you need to pay some declaration fee (for example if you use BLE and advertise it as BLE product)[/quote]

The Bluetooth Qualification fee ($10,350 starting in 2024), which effectively blocks hobbyists from commercializing their ideas at a small scale, is the whole reason why I want to use the Gazell protocol instead. My application does not require interoperability with devices from other manufacturers.

You'd think that module makers would capitalize on the idea of providing a module that uses a cost-free protocol stack, and have their products certified with Gazell-based firmware.

RE: Does custom firmware invalidate FCC modular approval?

Susheel Nuguru — Mon, 11 Dec 2023 11:37:35 GMT

ecorm,

What we certify is the hardware itself and the use of the RADIO by our protocol stack. Any application accessing the RADIO features though our qualified protocol only though the certified module hardware SHOULD not need any other certifications on your end but you need to pay some declaration fee (for example if you use BLE and advertise it as BLE product)

Yes, it is best to reach out to a local test house to shed more light very specific to your application.

RE: Does custom firmware invalidate FCC modular approval?

ecorm — Fri, 08 Dec 2023 19:51:06 GMT

Thank you for the prompt response.

[quote userid="6207" url="~/f/nordic-q-a/106449/does-custom-firmware-invalidate-fcc-modular-approval/459531"]but it also depends on what kind of extra certification the module makers are providing[/quote]

Could you elaborate what you mean by "extra certification"? I don't understand how a module can be "extra" certified. The way I understand it, it's either certified, or it's not.

[quote userid="6207" url="~/f/nordic-q-a/106449/does-custom-firmware-invalidate-fcc-modular-approval/459531"]you need to call the module maker to be sure about which your concerns[/quote]

The only response I got from one of the module makers is "you can use a different protocol stack without violating FCC certifications." While that's good to know, the extreme brevity of the response is not entirely convincing.

Another module maker would not even give me the time of day unless I provided them with production forecasts and estimates. While it does have potential for commercialization in a niche market, this is currently a side project for me.

I'll try contacting a test house to see if they can help shed some light on my question.

RE: Does custom firmware invalidate FCC modular approval?

Susheel Nuguru — Fri, 08 Dec 2023 13:53:50 GMT

[quote user=""]More specifically I would like to use a certain pre-approved nRF52805 module, but it comes preloaded with BLE firmware and an AT command interface that allows it to be customized somewhat.[/quote]

The certificationm most likely will not become invalid but you might need to do some other minor certification for your application. Buying a certified module should not restrict you from flashing your own firmware on the module, but it also depends on what kind of extra certification the module makers are providing and you need to call the module maker to be sure about which your concerns. We cannot answer this for the module makers.