Not receiving tx notification (NUS service) from second peripheral.

Question

I have a central device (nRF52832/Soft device s132) that connects to two peripherals. Both peripherals send data to the central via NUS. I have incorporated the required changes for the NUS_C by refering to the LBS_C service from multi-link central example. 
 Declaration: 
 BLE_NUS_C_ARRAY_DEF(m_ble_nus_c, NRF_SDH_BLE_CENTRAL_LINK_COUNT);
BLE_DB_DISCOVERY_ARRAY_DEF(m_db_disc, NRF_SDH_BLE_CENTRAL_LINK_COUNT); 
 
 Initialization: 
 static void nus_c_init(void) {
 ret_code_t err_code;
 ble_nus_c_init_t init;

 init.evt_handler = ble_nus_c_evt_handler;

 for (uint32_t i = 0; i < NRF_SDH_BLE_CENTRAL_LINK_COUNT; i++)
 {
 err_code = ble_nus_c_init(&m_ble_nus_c[i], &init);
 APP_ERROR_CHECK(err_code);
 }
}

static void db_disc_handler(ble_db_discovery_evt_t *p_evt) {
 ble_nus_c_on_db_disc_evt(&m_ble_nus_c[p_evt->conn_handle], p_evt);
}

Handler function: 
 static void ble_nus_c_evt_handler(ble_nus_c_t *p_ble_nus_c, ble_nus_c_evt_t const *p_ble_nus_evt) {
 ret_code_t err_code;

 switch (p_ble_nus_evt->evt_type) {
 case BLE_NUS_C_EVT_DISCOVERY_COMPLETE:

 err_code = ble_nus_c_handles_assign(p_ble_nus_c, p_ble_nus_evt->conn_handle, &p_ble_nus_evt->handles);
 APP_ERROR_CHECK(err_code);
 
 err_code = ble_nus_c_tx_notif_enable(p_ble_nus_c);
 APP_ERROR_CHECK(err_code);
 break;

 case BLE_NUS_C_EVT_NUS_TX_EVT:
 ble_nus_chars_received_uart_print(p_ble_nus_evt->p_data, p_ble_nus_evt->data_len);
 break;

 case BLE_NUS_C_EVT_DISCONNECTED:
 NRF_LOG_INFO("Disconnected.");
 break;

 default:
 break;
 }
} 
 
 The snippet from the ble_evt_handler: 
 case BLE_GAP_EVT_CONNECTED:
 // Discover peer's services.
 err_code = ble_nus_c_handles_assign(&m_ble_nus_c[p_gap_evt->conn_handle], p_ble_evt->evt.gap_evt.conn_handle, NULL);
 APP_ERROR_CHECK(err_code);

 err_code = ble_db_discovery_start(&m_db_disc[p_gap_evt->conn_handle], p_ble_evt->evt.gap_evt.conn_handle);
 APP_ERROR_CHECK(err_code);
 break;
 } 
 
 I can see both the peripherals getting connected. Both peripherals stream data from on-board sensors distinguishable from the sensor Id. The issue is, I see the data only from the peripheral that connects first. If peripheral 1 connects first, i only see the data from peripheral 1. If peripheral 2 connects first then I see the data only from peripheral 2. In the function: 
 static void ble_nus_c_evt_handler(ble_nus_c_t *p_ble_nus_c, ble_nus_c_evt_t const *p_ble_nus_evt) 
 I am printing the address of the p_ble_nus_c using: 
 NRF_LOG_INFO("nus instance = %u.", p_ble_nus_c); 
 When the nus handler runs for the case BLE_NUS_C_EVT_DISCOVERY_COMPLETE, I see two different instances, like these - 
 nus instance = 536900620 - from peripheral 1, and 
 nus instance = 536900636 - from peripheral 2 
 
 But w hen the nus handler runs for the case BLE_NUS_C_EVT_NUS_TX_EVT, I only see 
 nus instance = 536900620 - which is the peripheral that was connected first. Is it possible to stream data from both the peripherals simultaneously? Is there something I am missing?

tinytrex · Answer

Found the issue. A global variable was being updated undesirably. This was supposed to be updated once upon BLE_NUS_C_EVT_DISCOVERY_COMPLETE event. However I was updating it outside of it so for every handler callback this was being updated. Now I see the data from both the NUS peripherals.