Hello everyone,
I'm developing an application for an nrf52840 with the nrf connect VS Code extension.
The application runs three threads. One to acquire 40 bytes of data from a sensor at a frequency of 400Hz, another to process those data, and a third to send the result through BLE notifications.
It is important to note that I shouldn't lose the synchronization with the sensor for the processing but I can send the processed data slower. Therefore I configured the BLE like this :
CONFIG_BT=y CONFIG_BT_DEBUG_LOG=y CONFIG_BT_PERIPHERAL=y CONFIG_BT_USER_DATA_LEN_UPDATE=y CONFIG_BT_ATT_PREPARE_COUNT=9 CONFIG_BT_BUF_ACL_TX_COUNT=9 CONFIG_BT_BUF_ACL_RX_SIZE=47 CONFIG_BT_CTLR_DATA_LENGTH_MAX=47 CONFIG_BT_L2CAP_TX_MTU=47 CONFIG_BT_BUF_ACL_TX_SIZE=47 CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT=7812
If my calculations are good, it should take 868µs to send a packet. But when I measure the time taken by the bt_gatt_notify it is around 20ms.
This slows all of my processes and therefore makes the FIFOs which are in charge of passing the data from one thread to another filled very quickly.
The FIFO is filled like this :
size_t size = sizeof(struct raw_tx_buf); char *raw_mem_ptr = k_malloc(size); __ASSERT_NO_MSG(raw_mem_ptr != 0); memcpy(raw_mem_ptr, &raw_tx, size); k_fifo_put(&raw_tx_fifo, raw_mem_ptr);
And read like this :
struct raw_tx_buf *raw_buf = k_fifo_get(&raw_tx_fifo,K_FOREVER); bt_gatt_notify(NULL,&mcd_svc.attrs[2],raw->raw_data,sizeof(raw->raw_data); k_free(raw_buf);
If I can't make the notification function go faster, how can I prevent the overfilling of the FIFO which makes everything crash ?
Thanks in advance for your answer.
