Tx power level change not reflected in Tx Power Service

RE: Tx power level change not reflected in Tx Power Service

Kenneth — Sun, 20 Sep 2020 15:54:26 GMT

I was not aware, but this sounds like a reasonable workaround yes, you can also set the m_tps.conn_handle = BLE_CONN_HANDLE_INVALID; on the BLE_GAP_EVT_DISCONNECTED event if you want.

RE: Tx power level change not reflected in Tx Power Service

Saxman58 — Fri, 18 Sep 2020 06:16:33 GMT

You are right. It was returning a BLE_ERROR_INVALID_CONN_HANDLE. This was happening when I changed the power level when unconnected.

I see that other services prevent this problem by either setting the conn_handle to BLE_CONN_HANDLE_INVALID in their service init routine, or they call sd_ble_gatts_value_set() with a first parameter of BLE_CONN_HANDLE_INVALID rather than the current service conn_handle.

For example, the Blood Pressure Service init looks like this:

uint32_t ble_bps_init(ble_bps_t * p_bps, ble_bps_init_t const * p_bps_init)
{
...

    p_bps->conn_handle = BLE_CONN_HANDLE_INVALID;
...
}

The Battery Service takes the other approach in their wrapper around sd_ble_gatts_value_set():

ret_code_t ble_bas_battery_level_update(ble_bas_t * p_bas,
                                        uint8_t     battery_level,
                                        uint16_t    conn_handle)
{
    ...
    
    if (battery_level != p_bas->battery_level_last)
    {
        ...
        
        // Update database.
        err_code = sd_ble_gatts_value_set(BLE_CONN_HANDLE_INVALID,
                                          p_bas->battery_level_handles.value_handle,
                                          &gatts_value);
    ...
}

The Tx Power Level Service ble_tps.c library code does neither, so an error is thrown when setting without a connection. Should the library code be more like the others? My workaround is to set the conn_handle after calling the library ble_tps_init() function:

    err_code = ble_tps_init(&m_tps, &tps_init_obj);
    m_tps.conn_handle = BLE_CONN_HANDLE_INVALID;

And when it is connected, setting the gatt value through ble_tps_tx_power_level_set() is indeed reflected in the value the host sees.

RE: Tx power level change not reflected in Tx Power Service

Kenneth — Thu, 17 Sep 2020 11:51:05 GMT

I suspect that ble_tps_tx_power_level_set() is returning an error code here, and that the error check by APP_ERROR_CHECK() cause the application to assert to the fault handler. It would be good if you can find the error code from ble_tps_tx_power_level_set(). The ble_tps_tx_power_level_set() is basically a wrapper around sd_ble_gatts_value_set(), so I guess it is one of the listed errors:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s140.api.v6.0.0/group___b_l_e___g_a_t_t_s___f_u_n_c_t_i_o_n_s.html#ga2760c51ea71853bd74e2e7e7117ef52a