Hi
I am working on direction finding examples, based on CTE feature that is introduced in BLE v5..
I have build and run both "tx" and "rx" examples successfully as described here:
My Configuration:
Using nRf Connect SDK v1.6.0
Both tx and rx running on nRF52833-DK
Both tx and rx are used in AoA mode.
Then I tried to change the antenna pattern (main.c of the rx project) from:
static const uint8_t ant_patterns[] = { 0x2, 0x0, 0x5, 0x6, 0x1, 0x4,
0xC, 0x9, 0xE, 0xD, 0x8, 0xA };
to this pattern (one item has appended):
static const uint8_t ant_patterns[] = { 0x2, 0x0, 0x5, 0x6, 0x1, 0x4,
0xC, 0x9, 0xE, 0xD, 0x8, 0xA, 0x8 };
which causes an error at the run time (printed to the terminal by rx device):
. . . success. Periodic sync established. Enable receiving of CTE... failed (err -22) . . .
By investigating the source code, I found the problem has raised from "validate_cte_rx_params" function, implemented in "/ncs/zephyr/subsys/bluetooth/host/direction.c"
static int validate_cte_rx_params(const struct bt_df_per_adv_sync_cte_rx_param *params)
{
...
if (params->num_ant_ids < BT_HCI_LE_SWITCH_PATTERN_LEN_MIN ||
params->num_ant_ids > df_ant_info.max_switch_pattern_len || !params->ant_ids) {
return -EINVAL;
}
...
return 0;
}
Somewhere in lower layers, the maximum number of antenna pattern has been set to 12. so appending a new item to antenna pattern raises an error when it is higher than this predefined maximum number.
This "df_ant_info.max_switch_pattern_len" has been initialized in "int le_df_init(void)" function and reads the lower layer values by "hci_df_read_ant_info" function.
-------------------------------------------------
Now my question is:
Is this limitation a software issue or a hardware one? How can I use an antenna pattern that has more than 12 elements?
Thanks
