Custom STM32WB55 BLE+Zigbee board can only connect 4 devices max

[RIOD_HW]

Hi , 

I have designed one product with STM32WB55 for BLE and Zigbee concurrency. 

The schematic design I have followed is the with out SMPS design (LDO mode). VFBSMPS, VLXSMPS, VDDSMPS pins are connected to VDD. 

Our firmware will scan for BLE devices and it works in Nucleo development board. But not functional in our custom board. 

With our board it is able to connect upto 4 devices only, but the same firmware can handle up to 18 devices in development board. 

What will be the reasons for this ? 

[Ouadi · Accepted solution]

Hello @RIOD_HW,

The architecture design with no SMPS should allow to support up to 8 BLE links making no difference with SMPS enabled. 

• The maximum number of concurrent BLE connections is determined by:
  • The wireless stack version and configuration (CPU2 firmware)
  • The resources allocated (link context, buffers, etc.)
• Whether the internal supply is SMPS or LDO does not change those internal limits

On the other side, the power architecture may affect the RF performance as well as the matching antenna..Have you done any RF performance test to validate your design ?

Which exact wireless binary (stm32wb5x_*.bin) you are using ?

Best regards,

Ouadi