BSoM B524 EMC test modes for cellular and bluetooth

We are planning some radio EMC precompliance tests for a product based on the B524.

We are aware of Certifications | Datasheets | Particle, but it seems unclear if we can completely omit EMC testing for cellular and bluetooth.

We got the information from the test lab that the DUT needs to support some test modes but I could not find information in the Particle docs about that.

  • Does the eSIM support MNC 01 and MCC 001?
  • How can a “Bluetooth EMC test mode” be enabled?

We have been told by the test lab that these two points are necessary. They said the cellular test mode will be enabled externally but the SIM has to support 01 and 001. They have test SIMs for that but the B524 has no sim slot. About the Bluetooth test mode they said that it has to be activated by the device software.

Thank you for any help.

I made some progress here.

For Bluetooth, the Direct Test Mode (DTM) can be enabled by flashing a DTM-Firmware with the Particle Debugger. This overwrites Particle software on the device. The nRF SDK includes a DTM example which can be used. I had to add some code to change the baudrate for the control UART from 115200 to the DTM standard baudrate of 19200.

For cellular, I think the device needs to have a test sim. The B524 does not have a SIM slot, but the SIM pins are routed to the connector and there seem to be some resistors to connect an external sim instead of the eSIM: B Series B524/B523 datasheet | Datasheets | Particle
I have not tested this yet.


For test SIMs we usually either replace the SMD SIM on the SoM with a MFF2 test SIM, or use an adapter.

The adapter is a flexible PCB with the same pads as the SMD SIM on one end, and a 4FF nano SIM socket on the other end. You unsolder the Particle SIM, solder the adapter in place, then put the test SIM in the 4FF slot.

You could put a 4FF SIM card socket on your base board and move the resistors on the SoM as well.

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Reach out to and specifically ask for the certification lab test instructions. We will then send those on over. This is a common question and we have detailed instructions and can answer your test lab requests more in depth.

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