Nrf Connect SDK peripheral always reads RSSI as 127 upon a connection

[CodeLoader]

Hello, I'm using an nRF5340 board with nRF Connect SDK as a BLE peripheral device, and I'm trying to get RSSI value when another device connects to it.

So I'm trying to read it as in the Zephyr hci_pwr_ctrl example. Specifically, I'm calling this function in the connection handler:

bt_hci_cmd_send_sync(BT_HCI_OP_READ_RSSI, requestBuffer, &responseBuffer);

Note that I'm using SoftDevice BLE stack on the CPU_NET, and my code runs on the CPU_APP.
And I have created a hci_rpmsg.conf in the child_image folder, which has the following lines:

CONFIG_BT_LL_SOFTDEVICE_DEFAULT=y
CONFIG_BT_LL_SOFTDEVICE_VS_INCLUDE=y
CONFIG_BT_LL_SOFTDEVICE=y

CONFIG_BT_EXT_ADV=y
CONFIG_BT_CTLR=y
CONFIG_BT_CTLR_ADV_EXT=y
CONFIG_BT_EXT_ADV_MAX_ADV_SET=2
CONFIG_BT_CTLR_PHY_CODED=y
CONFIG_BT_CTLR_ADVANCED_FEATURES=y
CONFIG_BT_CTLR_CONN_RSSI=y
CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y

And I also have flashed merged_CPUNET.hex to the board, so that CPU_NET runs with these settings.

Now, the function to read RSSI runs without any errors, it returns 0 as error code, and it always gives the value of RSSI equal to 127, irrelevant of the distance and signal strength shown in NRF Connect. 

So, this code:

auto* commandResponse = reinterpret_cast<bt_hci_rp_read_rssi*>(responseBuffer->data);
printk("Rssi %d, status %u, handle %u\n", commandResponse->rssi, commandResponse->status, commandResponse->handle);

Produces the following log upon connection:

00> Req rssi for handle 14
00> 
00> Rssi 127, status 0, handle 14

What can be done to read RSSI properly?

[Einar Thorsrud]

I see the same in nRF Connect SDK 1.6.1. There is no error indicating that it is not ready (the status still indicates 0). This is fixed in 1.7 and later, though. For 1.6 I suggest you simply discard 127 as that can never be a valid value.