Electronics Design AUUsing a certified ESP32 module — why does the complete product still need CISPR 32 testing for RCM?
Asked by stale_biscuit_03 ·
We're building a commercial IoT product around an ESP32-WROOM-32E. Did a bit of research and found the module in the ACMA compliance labelling database — it's got an RCM registration. I assumed that meant our product was covered for RCM compliance as long as we didn't modify the RF part.
Called a NATA-accredited lab last week to get a quote and timeline for getting our product certified. The person I spoke to said we need to bring the complete product in for CISPR 32 testing anyway — not just for radio, but for "conducted and radiated emissions from the host board." I nodded along but honestly didn't fully follow why the module's existing RCM certification doesn't just cover us.
We're a small team and this is our first product going to market in Australia. Can someone explain what the module cert actually covers vs what we still need to test? Is the lab right that we need a full CISPR 32 run even though the radio module is already certified?
3 Replies
The lab is correct, and this is probably the most common misunderstanding I come across with Australian IoT companies doing their first product launch.
The ESP32-WROOM-32E's ACMA registration covers its intentional radio emissions — specifically, the 2.4 GHz Wi-Fi and Bluetooth transmissions from the module's own RF front-end, tested under the conditions defined at the module's certification testing (a specific reference host board, specific antenna orientation, specific operating modes). That registration protects you from needing to do full Radiocommunications Act certification for the radio transmitter itself.
What it does not cover:
- The non-intentional emissions from your host board: your MCU clock harmonics, your switching power supply (buck converter, LDO, whatever you're using), your oscillator, your I2C and SPI buses running at multi-MHz rates
- The conducted emissions injected into the supply rails from your power conversion circuitry
- Any cable antenna effects from the cables you've attached (USB, serial, power)
These are entirely separate from what the radio module transmits. CISPR 32 tests your complete product as a system — everything plugged in, all cables attached, running its normal operating firmware. The module's radio could be transmitting perfectly within its certified limits at the same time your switching regulator is pushing harmonic noise at 200 MHz, and the CISPR 32 limits would still be exceeded.
As the responsible supplier placing this product on the Australian market, you're the one who signs the Declaration of Conformity asserting the complete product meets the applicable standards. The module's existing certification is evidence about the module; your DoC covers the whole system.
For the full breakdown of exactly where the module's certification boundary ends and what the host board must still address — including the compliance path by module type (ESP32, nRF52840, cellular, LoRa) — see what a pre-certified radio module's ACMA certification covers and what it doesn't. The RCM certification process overview covers how these steps fit together from design through to ACMA registration.
To add the technical context to rcm_regs_rex's accurate summary:
CISPR 32 (the standard that applies to most commercial electronics products in Australia) splits emissions testing into two categories. Conducted emissions runs from 150 kHz to 30 MHz and measures the noise your product injects back into its supply wiring via a LISN. Radiated emissions runs from 30 MHz to at least 1 GHz and measures the electromagnetic fields your product radiates into free space.
The ESP32 module's intentional 2.4 GHz transmissions are tested under a completely different framework — the radio certification. From a CISPR perspective, your test lab treats the module as just another digital circuit sitting on the board. The switching regulator on your host PCB, the clock oscillator, the crystal, the MCU switching its GPIO lines — those are what the formal CISPR test is looking for.
One practical note: I'd strongly recommend doing an informal pre-compliance scan before booking the formal NATA lab session. A near-field probe and a spectrum analyser can show you where your dominant emissions are coming from, at a fraction of the formal test cost. If your buck converter switching loop is large, or your MCU crystal is sitting on a long trace without guard, you'll find it in pre-compliance and fix it before it fails in the formal test. See how to conduct EMC pre-compliance testing for what that involves.
Also worth mentioning: if the host board layout around the ESP32 antenna area is significantly different from the module's reference host board (the one used for certification), there's a question of whether the module's certified antenna performance still holds. Most labs won't flag this as a CISPR issue — it's a radio performance question — but it's worth noting.
One addition from a documentation standpoint, since you mentioned this is your first product to market:
When the CISPR 32 testing is done and you're ready to prepare the Declaration of Conformity, the DoC needs to reference the accredited test report for your product — not the module's ACMA registration number. The module's registration is evidence that the module's radio is compliant. The DoC you sign as the responsible supplier declares that your complete product (name, model number, as supplied) conforms to AS/NZS CISPR 32. Those are two separate declarations.
The checklist at that stage:
- NATA-accredited CISPR 32 test report for your product → in your TCF
- DoC referencing that report, signed by your Australian entity
- RCM mark on the product label
- ACMA compliance labelling registration (the module's existing one covers the radio transmitter; check with your lab whether anything additional is needed for the host product registration)
The Declaration of Conformity requirements page covers what each field in the DoC needs to contain and who qualifies as the responsible supplier, which is worth reading before you sit down to write it.
Good luck with the testing — if you've already done some layout work to minimise switching loop area and keep your ground plane solid, you'll probably be fine first pass.