2385523_en-US

[#1]

MCXW71 - Packet loss and instability at 2 Mbps half-duplex due to 2.4 GHz co-existence / RF robustne

Hi NXP Community,

I am currently working on a project using the  #MCXW71C wireless MCU. I have developed a half-duplex communication protocol between two MCXW71C chips running at a 2 Mbps data rate.

While the communication is perfectly stable in a clean RF environment, I am experiencing severe instability and significant packet loss as soon as other 2.4 GHz RF devices (such as smartwatches, wireless earbuds, or smartphones with Bluetooth enabled) are brought close to our hardware (within a distance of about 30 cm).

Here are some important details about our setup:

Hardware: This is a custom PCB design (not an evaluation board). We designed and implemented the impedance matching network ourselves for the RF front-end.

PHY / Protocol: GENFSK NXP

SDK Version: SDK_2.25.09.00_MCXW716C

Frequency Hopping: not us FHSS

Given that our custom board works well in isolation but suffers in congested RF environments, we suspect the receiver might be desensitized or saturated by adjacent 2.4 GHz interferers.

Could you please provide some guidance?

Are there specific hardware tuning guidelines or registers for the MCXW71 to optimize receiver selectivity, AGC (Automatic Gain Control) behavior, or LNA gain in noisy environments?

Is there a recommended software Coexistence configuration or CCA (Clear Channel Assessment) threshold tuning to better handle packet collisions?

Could a slight mismatch in our custom impedance network degrade the selectivity/blocking performance of the transceiver specifically in the presence of strong out-of-band/adjacent interferers?

Board DesignRe: MCXW71 - Packet loss and instability at 2 Mbps half-duplex due to 2.4 GHz co-existence / RF robu

Hello,
Hope you are doing well.

Since you are using a custom board, I would recommend comparing its performance against the FRDM-MCXW71 under the same conducted test setup. Before modifying radio registers, it is important to verify factors such as the RF layout, grounding, antenna matching network, power supply noise, and any enclosure-related coupling effects.

You can also run PER tests while sweeping the CCA threshold to find a practical operating point. CCA can help reduce packet collisions by preventing transmission when the channel is already busy, but the threshold should be validated empirically in the target RF environment.

The following document describes RF performance testing methods and how to use them to evaluate CCA behavior: AN14399 MCXW71 Connectivity Test for 802.15.4 Applications

To further validate your RF design, you may also find the following documents useful:

UG10146 MCXW71 Hardware Design Guide

AN14374 FRDM-MCXW71 RF System Evaluation Report for Bluetooth LE and IEEE 802.15.4 Applications

AN2731 Compact Planar Antennas for 2.4 GHz Communication

Best regards,
Sofia.