Automatically switching between 1Mbps, 2Mbps and coded Phys

RE: Automatically switching between 1Mbps, 2Mbps and coded Phys

Vidar Berg — Mon, 18 Jun 2018 05:59:39 GMT

Good idea to use the pm to store PHY support for peer devices. With regards to receiver sensitivity, 6 dB difference will actually have a significant impact on range even though it doesn't sound like much (40 % increase in theory, likely less in practice).

RE: Automatically switching between 1Mbps, 2Mbps and coded Phys

goldwake — Thu, 14 Jun 2018 21:18:06 GMT

Thanks Vidar. I've implemented this and keep track of which PHYs the device supports using ble_conn_state flags. It works pretty well. If it's a bonded peer, I also store these using pm_peer_data_app_data_store

Looking at the receiver sensitivities seems to show that I can use 2Mbps PHY at almost the same range of dBm as 1Mbps

RE: Automatically switching between 1Mbps, 2Mbps and coded Phys

Vidar Berg — Thu, 14 Jun 2018 12:21:55 GMT

Hi,

I think the RSSI can be a good indicator for determining what PHY to use. Sampling of RSSI is started by calling sd_ble_gap_rssi_start() as you said, and BLE_GAP_EVT_RSSI_CHANGED will be reported once the RSSI crosses the chosen threshold.

I'm not sure what the best time to switch phy would be, maybe 5-10 dB below max. receiver sensitivity, or more if the device can get quickly out of range.

It's not possible to check which modes the peer device support without sending a phy update request.