Cant read characteristic value without pointer

[Daniel Dakhno]

I have two functions, which both try reading incoming data for a characteristic.

I would expect 

*data

be the same address in both functions, since the p_ble_evt write struct should just be copied byte by byte to the memory allocated for write_evt in the broken case.

Am I understanding the = operator wrong?

Does 

struct copy = existingStructInstance;

not copy the contents from existingInstance to copy?

Does this have something to do with data being declared as 

(uint8_t data[1]) instead of (uint8_t *data) ?

void read_broken(ble_evt_t *p_ble_evt) {
    ble_gatts_evt_write_t write_evt = p_ble_evt
        ->evt
        .gatts_evt
        .params
        .write;

    NRF_LOG_DEBUG("broken write address: %x\n", (uint32_t) write_evt.data);
}

void read_working(ble_evt_t *p_ble_evt){
    ble_gatts_evt_write_t *write_evt = &p_ble_evt
        ->evt
        .gatts_evt
        .params
        .write;

    NRF_LOG_DEBUG("working data address: %x\n", (uint32_t) write_evt->data);
}

[Kazi Afroza Sultana]

Hello,

ble_gatts_evt_write_t *write_evt = &p_ble_evt , this one is correct as the write_evt pointer will take the address of p_ble_evt (Pointer to the event received from BLE stack). 

Thanks,

Best Regards,

Kazi Afroza Sultana

[Daniel Dakhno]

I don't quite see how that answers my question of why the copying using the "=" operator doesn't work.

[Kazi Afroza Sultana]

Hello,

I am not clear about your question.

''be the same address in both functions, since the p_ble_evt write struct should just be copied byte by byte to the memory allocated for write_evt in the broken case.

Am I understanding the = operator wrong?''

Do you mean to copy large amount of data to memory? 

BR

Kazi