RE: How to get the characteristic data with array?

Max Liao — Tue, 17 Jul 2018 03:40:17 GMT

Hi Edvin

Thanks for your help, now I known relation of that.

The problem has resolved, thanks.

RE: How to get the characteristic data with array?

Edvin — Mon, 16 Jul 2018 14:40:29 GMT

Hello,

If you see in the ble_gatts.h file in the SDK on line 353 (in SDK15), it says:

  uint8_t                     data[1];            /**< Received data. @note This is a variable length array. The size of 1 indicated is only a placeholder for compilation.
                                                       See @ref sd_ble_evt_get for more information on how to use event structures with variable length array members. */

So the data coming at the event is longer than 1 byte. The length of the array is

ble_gatts_evt_write_t->len;

the 1 is only a placeholder for the compilator.

You can check out the ble_app_uart example found in SDK\examples\ble_peripheral\ble_app_uart. In main.c, you will see a function called nus_data_handler(...)

It is actually a ble_gatts_evt_write_t event, but it is "translated" to a NUS (Nordic UART Service) event in ble_nus.c, in the on_write() function, then calling the nus_data_handler(...) with the translated event.

You can see that

evt.params.rx_data.p_data = p_evt_write->data;

evt.params.rx_data.length = p_evt_write->len;

and that these are used in the nus_data_handler(...) in main.c.

Best regards,

Edvin