Received indication data corrupt

RE: Received indication data corrupt

Martin Ziel — Tue, 12 Jun 2018 15:27:48 GMT

Thank you very much, this solved my issue!

RE: Received indication data corrupt

tesc — Tue, 12 Jun 2018 14:41:32 GMT

Hi,

You should not declare the variables for the ble_gap_evt_t pointer and the ble_gattc_evt_hvx_t event structure const. It looks like removing the const keywords on those two lines should make things work as intended.

Regards,
Terje

RE: Received indication data corrupt

Martin Ziel — Mon, 11 Jun 2018 13:25:26 GMT

Thank you for your answer. I excluded the sending side as the source of the error, because I have a working communication with a mobile and linux application. I've suspect it's a memory layout problem or something with the interrupts of the softdevice, because the data is already corrupt when I read it from the hvx event.

I've stripped the code down to the relevant bits:

static uint32_t progress = 0;
static uint8_t received_data[80];

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
    uint32_t              err_code = 0;
    const ble_gap_evt_t * p_gap_evt = &p_ble_evt->evt.gap_evt;

    switch (p_ble_evt->header.evt_id)
    {
        case BLE_GATTC_EVT_HVX:
            ;const ble_gattc_evt_hvx_t hvx_evt = p_ble_evt->evt.gattc_evt.params.hvx;
            if(app_state == as_RECEIVE_DATA) {
                memcpy((void*)(&received_data[progress]), hvx_evt.data, hvx_evt.len);
                NRF_LOG_INFO("Received indication data:\r\n");
                    for(int i = 0; i < hvx_evt.len; i++) {
                        NRF_LOG_RAW_INFO("%02x", hvx_evt.data[i]);
                }
                NRF_LOG_INFO("\r\n");
                progress += hvx_evt.len;
            }
            if(hvx_evt.type == BLE_GATT_HVX_INDICATION) {
                err_code = sd_ble_gattc_hv_confirm(connection_handle, hvx_evt.handle);
                APP_ERROR_CHECK(err_code);
            }
            break;
    }
}

Edit: I've written a small test case using another controller which sends out the string "Hello" via indication. On my receiving nRF51822, I only get He???, so I'm confident that the issue lies in the receiving end.

RE: Received indication data corrupt

tesc — Mon, 11 Jun 2018 12:49:51 GMT

Hi,

It is hard to tell without the source, but it sounds like something that could happen if the variable holding the data, either on the sending or receiving side, goes out of scope. Since the APIs work with pointers, it is important that the data is not placed somewhere in memory that gets popped off the stack once the function returns. That usually means the variable holding the data (in both ends) should be a "static uint8_t" array.

Regards,
Terje