RE: when transfer long string using UART service (string length is over 300bytes.), BLE connection was disconnected by some error.

Martin Lesund — Thu, 31 May 2018 09:32:25 GMT

- What error ?

Please try to debug and provide any error codes/logs of what is happening.

RE: when transfer long string using UART service (string length is over 300bytes.), BLE connection was disconnected by some error.

dongsung kim — Mon, 28 May 2018 05:31:30 GMT

i did it with Throughput example as default config. that is OK.

but when i use ble_app_uart, i can't transmit long string data(300byte).

because there was occurred error and application is restarted again.

RE: when transfer long string using UART service (string length is over 300bytes.), BLE connection was disconnected by some error.

Martin Lesund — Tue, 22 May 2018 13:24:22 GMT

Hi Kim,

Check out the Throughput example and documentation of the different parameters you can change on how to increase the Throughput,.

The ATT_MTU Throughput Example shows how different connection parameters influence the throughput performance of BLE connections. The following parameters can be tuned:

ATT_MTU size: The default Maximum Transmission Unit (MTU) is 23 bytes. When increasing this value, longer ATT payloads can be achieved, increasing ATT throughput.
Data length: The default data length for a radio packet is 27 bytes. Data length extension allows to use larger radio packets, so that more data can be sent in one packet, increasing throughput.
Connection interval: The connection interval defines how often the devices must listen on the radio. When increasing this value, more packets may be sent in one interval, but if a packet is lost, the wait until the retransmission is longer. Increasing this value can increase throughput, provided that the GAP event length increases by the same amount or connection event length extension is enabled.
Physical layer (PHY) data rate: The over-the-air data rate used to be limited to 1 Ms/s in Bluetooth low energy. Starting with Bluetooth 5, higher data data rates are permitted to achieve faster transmission, and it is possible to use coded PHY (available on the nRF52840 SoC only) for long-range transmission.
Connection event length extension: This option controls if the SoftDevice should attempt to extend the radio time for connections in a connection interval. This can positively affect throughput by making it possible to send more packets in a connection interval. This effect increases with the duration of the connection interval.
GAP event length: This setting determines the duration of a connection event within a connection interval. Increasing this value can greatly affect the throughput.