NX40 Module Integration FAQ
This FAQ covers common questions when integrating NX40 into a custom PCB.
This FAQ focuses on module integration. BLE application behavior, GATT design, low-power tuning, and 802.15.4 / Thread planning are covered in the NX40 Series BLE Module section.
Model Selection
Which NX40 model should I choose?
Choose based on antenna type and external Flash requirement.
| Requirement | Direction |
|---|---|
| Integrated chip antenna | Choose NX40i variant |
| External antenna | Choose NX40E variant |
| External Flash required | Choose 32 model |
| No external Flash required | Choose 00 model |
See:
What is the difference between 32 and 00 models?
| Model Code | Flash Option |
|---|---|
32 | External 32 Mbit SPI Flash |
00 | No external Flash |
Use a 32 model if the firmware or application requires external storage. Use a 00 model only when the firmware can run without external Flash.
PCB Bring-up
The board does not power on. What should I check?
Check:
| Area | Check |
|---|---|
| Power rail | Confirm correct voltage from NX40 schematic/datasheet |
| GND | Confirm ground continuity |
| Short circuit | Check power-to-ground resistance before power-on |
| Decoupling | Confirm capacitors are installed near power pins |
| Assembly | Inspect for solder bridge or missing parts |
| Current limit | Use current-limited first power-on |
I cannot connect through SWD. What should I check?
| Signal | Check |
|---|---|
| SWDIO | Routed correctly and not shorted |
| SWDCLK | Routed correctly and not shorted |
| GND | Common ground between debugger and board |
| RESET / NRESET | Not held low unexpectedly |
| Target power | Board is powered |
| Target voltage reference | Connected if required by debugger |
Firmware flashes but does not run correctly. What should I check?
Possible causes:
| Cause | Check |
|---|---|
| Wrong board configuration | Confirm board target and pin mapping |
| Power instability | Measure power during boot |
| Reset issue | Check reset circuit |
| Flash mismatch | Confirm firmware matches 32 or 00 model |
| GPIO conflict | Check pin assignment and reserved functions |
| Clock issue | Review crystal and clock circuit |
Pad / Pin Layout
Which signals should always be accessible?
At minimum, keep access to:
| Signal | Reason |
|---|---|
| Power rail | Measurement and bring-up |
| GND | Measurement reference |
| SWDIO | Firmware programming/debug |
| SWDCLK | Firmware programming/debug |
| RESET / NRESET | Reset and recovery |
| UART log pins | Optional bring-up log path |
| Key GPIO | Application-specific validation |
Can Flash-related pins be used as GPIO?
It depends on the model and firmware configuration.
For 32 models, Flash-related pins may be required for external SPI Flash operation. For 00 models, confirm whether those pins are available in the firmware board configuration before using them as GPIO.
Antenna
BLE signal is weak on my custom PCB. What should I check?
| Area | Check |
|---|---|
| Module placement | Antenna side placed correctly |
| Keep-out | No copper, ground, battery, or metal in the antenna clearance area |
| Enclosure | Test with final enclosure |
| External antenna | Check connector, cable, and placement |
| RF path | Check controlled impedance and ground reference |
| Assembly | Inspect antenna and matching components |
Can I change antenna type after PCB layout?
Changing from chip antenna to external antenna, or changing module placement, can require PCB redesign and RF re-validation. Decide antenna type before final PCB layout.
Handling and Soldering
What should I inspect after reflow?
| Item | Purpose |
|---|---|
| Module alignment | Confirm correct placement |
| Solder joints | Check for bridge or insufficient solder |
| Mechanical damage | Check package and antenna area |
| Power-to-ground resistance | Detect shorts before power-on |
| Antenna area | Confirm no unexpected metal or contamination |
Can I clean the module after soldering?
Only follow the official NX40 handling guidance. Avoid ultrasonic cleaning, liquid immersion, or aggressive solvent cleaning unless explicitly approved.
Production
What should be included in production test?
Recommended checks:
| Test | Purpose |
|---|---|
| Power check | Confirm power rail and current behavior |
| SWD programming | Confirm programming access |
| Firmware boot | Confirm application starts |
| External Flash check | Required for 32 models |
| BLE advertising | Confirm radio operation |
| Current measurement | Detect abnormal load |
| Visual inspection | Confirm assembly quality |