I’m curious if Blues has any design guides or best practice notes that address physical orientation and wire routing for a Notecard Cell+Wifi within a product enclosure. In previous prototype designs, we’ve had issues with Simcom LTE/GPS modules causing interference on our highspeed data lines, which was remedied by trial and error of reorienting the module in relation to our MCU and data wiring. Would love to proactively avoid as much of that as possible with the Notecard.
Our scenario: Prototype design with multiple dev boards/modules stacked vertically in an enclosure. Notecard Cell+Wifi in a Notecarrier X, connected via I2C to an STM32 Nucleo host. Utilizing a high-speed CANBUS controller and multiple high-speed serial lines. We will be using three U.fl antenna pigtails extending from the Notecard to the back of the enclosure, connected to external LTE/WiFi/active-GPS antennas.
Any insight or tips are welcome, for example: With a previous module we worked with, flipping the board upside down relative to the host controller yielded the best results so that majority of signal spillage that emitted from the top of the module was facing away from our MCU and highspeed data lines. Another module we’ve used has substantially more emissions from one particular edge, so we learned to face that edge away from other components and route signal wiring away from it.
We don’t have any explicit design guides on these topics, but we do recommend your cellular and GPS antennas keep a 12mm diameter cylinder of “no metal” surrounding the core of the antenna to avoid interference.
Also, in the datasheets for our legacy Cellular Notecards (i.e. Notecards with the STM32 exposed on the front) we have this note re: bright light:
The performance of the STM32 microcontroller onboard the Notecard may be affected in the presence of extremely bright light including, for example, direct sunlight. Bright light may interfere with the semiconductor’s operation by generating unwelcome electrical currents, performance degradation, malfunction, or shutdown.
If you anticipate that bright light may shine on your Notecard in its deployed setting, we recommend you mount the Notecard in a shadow, or that you cover the STM32 microcontroller with an opaque tape to reduce light levels that may affect the semiconductor.
(Right after I posted this I realized you are using the Cell+WiFi Notecard which does NOT have this issue )
Thanks Rob. Does that recommendation about the antenna include the U.fl-to-SMA connectors, or only the core/emitter at the end of the cable? All 3 of our antennas are external with cables that allow them to be outside of the metal enclosure that the product sits within. So we’re really more focused on potential interference within the enclosure caused by emissions from the Notecard itself or its wiring. Thanks.
Yes, it would include the u.FL connectors as well on the Notecard and Notecarrier (but those have already been designed with placement to minimize interference).
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