Gazelle & NRF 52840

RE: Gazelle & NRF 52840

Kenneth — Fri, 27 Mar 2026 10:02:42 GMT

Sorry, you are right. I was under the impression it was, but it's been a while since I worked on Gazell so my memory proved me wrong.

The GZP API doesn't provide a specific high-level function for host-to-device encrypted data because it uses the underlying Gazell ACK mechanism. For encrypted host-to-device communication, you need to manually encrypt the ACK payload data before calling nrf_gzll_add_packet_to_tx_fifo() on the host. So maybe that can help.

Kenneth

RE: Gazelle & NRF 52840

Samuel01 — Fri, 27 Mar 2026 08:23:13 GMT

If you have a look at the gzp.h, you will see for the host the functions

gzp_crypt_user_data_received and

gzp_crypt_user_data_read.

And for the device the function

gzp_crypt_data_send.

But there is no send function for the host, or attach_payload function.

RE: Gazelle & NRF 52840

Kenneth — Thu, 26 Mar 2026 19:29:22 GMT

I honestly don't understand, I can't imagine that it's encrypted only one way.

I assume you have a gazell host that is receiving data and a gazell device transmitting data, all communication should be done on pipe1 that is encrypted after gazell pairing. The gazell device is the one that need to initiate all communication. The gazell host can at any time prepare data to be sent on pipe1 back to the gazell device, but the only way it can be sent from the host to the device, is by the gazell device transmitting a packet which indirectly will then fetch the packet from the gazell host.

Kenneth

RE: Gazelle & NRF 52840

Samuel01 — Thu, 26 Mar 2026 15:29:47 GMT

Yes it's also what I found, only 1 pipe is encrypted, so it's not possible to have encrypted or at least authentified communication in both directions.

RE: Gazelle & NRF 52840

Kenneth — Thu, 26 Mar 2026 15:10:51 GMT

If I remember correctly then you can use pipe1 for encrypted data and pipe2-7 for unencrypted data. While pipe0 is used for pairing and key exchange.

Kenenth

RE: Gazelle & NRF 52840

Samuel01 — Thu, 26 Mar 2026 13:09:27 GMT

Hello,

Thanks for your reply, I have already checked this documentation. Unfortunately, when I try to communicate in encrypted way, there is no function available to add a payload to the ack. It seems this payload is used for key exchange.

RE: Gazelle & NRF 52840

Kenneth — Thu, 26 Mar 2026 13:01:14 GMT

Hello,

You can read more about how the Gazell transport layer works here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/gazell/gzll.html

You can read more about how the Gazell pairing library ensure secure wireless link between two devices here: https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/protocols/gazell/gzp.html

It's fully possible to meet your requirements using Gazell pairing.

Kenneth