nRF54L15 proprietary mode: Custom 250 kbps FSK configuration for legacy device (non-nordic) compatibility

[dp]

I'm developing a solution using nrF54L15 that needs to receive packets from existing legacy RF devices in the field that cannot be modified.

Required RF Parameters:

• Modulation: 2-FSK
• Data rate: 250 kbps

My Research So Far:

• nRF54L15 supports "proprietary 2.4 GHz protocols" with documented rates of 1M/2M/4M bps
• IEEE 802.15.4 mode uses 250 kbps but with O-QPSK (not FSK)
• Bluetooth LE modes use GFSK but at different rates (125k/500k/1M/2M bps)

Questions:

1. Can the nRF54L15's radio peripheral be configured for 250 kbps FSK modulation in proprietary mode or any custom mode available?
2. Are frequency deviation and channel spacing parameters configurable for custom applications?
3. Are there low-level register configurations that might enable custom FSK parameter settings?
4. Would oversampling approaches (receiving 250k signal with 1M FSK mode) be viable?

Any guidance on radio configuration flexibility or examples would be greatly appreciated.

[Kenneth]

Hi,

Unfortunately there is no mode that allow the radio to communicate over 250kbps like on the legacy nRF24L or nRF51 did.

Kenneth

[dp]

Hey Kenneth, thanks for your response.

Yes, I understand that there is no direct mode supporting 250kbps FSK. I was wondering if there is a way I can directly write to some low-level registers that might help me achieve similar functionality to what we had in legacy designs. Or please let me know if it's possible to achieve in any other way with some workaround.

[Johnny Nguyen]

Hello,

I believe Kenneth is alluding to the delta between the MODE register/configuration for the Radio peripheral between nRF54L15 and nRF51/24.

(from the respective chip datasheets):

On the 51 the mode register had the 250K Proprietary config

But that has since been dropped off on newer devices, such as the 54L.

i.e. the new radio does not have a configurable setting for its MODE for that old legacy mode.

Best regards,