How to increase Data Rate

[Ferhat B]

Hi

We use ble_app_uart_pca10040 app. We have our own board has microcontroller and send data over uart to ble module (bmd350) There is Nrf52832. I want to send 32byte pack and 500pack in sec. Im very far to achive that.

Ferhat

[Ferhat B]

First of all I couldnt find where to make DLE on.

Im sending 126 bytes in one pack now. It not working over 158. I tried 147 bytes working fine.

For now with 126bytes in one pack;
---> #define NRF_BLE_GATT_MAX_MTU_SIZE 158
---> 1nrf_ble_gatt_att_mtu_periph_set(&m_gatt, 150);
---> #define BLE_GATT_ATT_MTU_DEFAULT 23

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I tried several values for INTERVALS for definitions below, For example i tested 7.5 as min and 20 as max. I didnnt get a positive effect.

#define MIN_CONN_INTERVAL MSEC_TO_UNITS(20, UNIT_1_25_MS)
#define MAX_CONN_INTERVAL MSEC_TO_UNITS(75, UNIT_1_25_MS)

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My problem is;

1. Im sampling 16byte data at 500Hz. (I have some additional data but these important)
2. 500Hz makes 2ms interval for sampling. (1/500)
3. Below 158 ATT MTU size, i can make 8 pack x 16 bytes = 128bytes
4. So sending interval became 8x2ms = 16ms
5. If i can send every 128bytes evey 16ms, all became perfect.
6. Im using iPad Air2 now but later i will use different options.

[Sigurd]

Actually the ble_app_uart in SDK 13 will by default try to enable DLE, and set it to NRF_BLE_GATT_MAX_MTU_SIZE + LL_HEADER_LEN. But you need to check the log to see if it was successfully increased (i.e. if the iPad accepted the increase or not.). As mentioned earlier, if you set the NRF_LOG_DEFAULT_LEVEL to DEBUG (#define NRF_LOG_DEFAULT_LEVEL 4 in sdk_config.h), you should be able to see the parameters that is negotiated between the central and peripheral.

If DLE is not support on the iPad, you will see the following values in the log:

nrf_ble_gatt:DEBUG:max_rx_octets: 27
nrf_ble_gatt:DEBUG:max_tx_octets: 27

Unfortunately, I believe that many iOS devices does not support DLE, so this will limit your data-rate / throughput you can achieve. But you will have to check what values the max_rx_octets/max_tx_octets is set to.