Notifying characteristic value with 80 bytes each 20 ms gives me a BLE_HCI_CONNECTION_TIMEOUT in nRF-Connect

[Esteban Gutiérrez Correa]

Hello,

I have a project in witch I want to send the data received from an Arduino by UART, this data has a size of a little bit less than 80 bytes, this data is received each 20 ms (a 32 kbps data throughput), I am sure I am getting this data.

I am updating (Notifying) this data in a characteristic value each time I get it from the arduino, and I am doing it like it is done in the Bluetooth low energy Characteristics, a beginner's tutorial.

The problem is that when I flash the code in the nRF51-DK or in a Red Bear - Nano, and try to connect to them I get a

BLE_HCI_CONNECTION_TIMEOUT

in pc nRF-Connect or a

Error 133 (0x85): GATT ERROR

in the mobile nRF-Connect, so I can't connect to my device.

If I puts the data to come more slowly, I mean the same 80 bytes each 250 ms (a 2.56 kbps data throughput) I can connect to my device and can see the notified value but the nRF-Connect only shows me 20 bytes instead of the 80, on the other hand if I disable the notification and read it manually I can get the 80 bytes in the characteristic value as shown in this images:

I wasn't sure If I had reach the max data throughput, but reading in the page 77 of the Soft Device 130 product specification I saw this:

So I had reach it for the low Bandwidth config, but I don't know if it is possible to config the Bandwidth.

One more thing I have seen is that in the nRF51-DK works better for the same program for different data throughput.

I was wondering if someone could help me to understand this, and recommend me somewhere to read about it or what to do in this case.

thanks.

Here is my project, HAR_Wireless_peripheral.zip

[Petter Myhre]

I'm not sure why you get the GATT error, but you probably get BLE_HCI_CONNECTION_TIMEOUT on the central because the peripheral is not responding. It is probably not responding because you it has reset in app_error_handler(). Try setting a breakpoint in app_error_handler() and see if you hit it.

Could you also include the code that implements the sending of data?

[Esteban Gutiérrez Correa]

Here is the part of my code that implements the sending of data:

void our_time_characteristic_update(ble_os_t *p_our_service,
		char *sensor_value) {

	if (p_our_service->conn_handle != BLE_CONN_HANDLE_INVALID) {
		uint16_t len = 80;
		ble_gatts_hvx_params_t hvx_params;
		memset(&hvx_params, 0, sizeof(hvx_params));

		hvx_params.handle = p_our_service->notify_char_handles.value_handle;
		hvx_params.type = BLE_GATT_HVX_NOTIFICATION;
		hvx_params.offset = 0;
		hvx_params.p_len = &len;
		hvx_params.p_data = (uint8_t*) time_value;

		sd_ble_gatts_hvx(p_our_service->conn_handle, &hvx_params);
	}
}   

for (;;) {
		if (receptionFinish) {
			our_time_characteristic_update(&m_our_service, ptrReception);
			receptionFinish = false;
		}
	}

I am going to attach the project in a .zip in the question.

[Esteban Gutiérrez Correa]

@Petter Myhre I notice that the error is that when I try to read the characteristic value the devices resets, but I don't know where, who or what makes it reset, so I think that it is the SD. I tried to hit the error in the app_error_handler(), printing a message in the function that call it (assert_nrf_callback()), but it doesn't print anything I don't Know what more to do

[Petter Myhre]

Strange that you don't get a hit in the handler. Have you increase the ATT MTU? If not, you will not be able to send 80 bytes with a single call to sd_ble_gatts_hvx(), only 20 bytes. You should also check the returned error code of sd_ble_gatts_hvx(), how do you know it is successfully called?

[Esteban Gutiérrez Correa]

I checked the returned error code of the sd_ble_gatts_havx(), and the returned value has the same behavior like in this question strange error code 13313 (0x3401) returned by sd_ble_gatts_hvx(), and in this question I notice that I only able to send 20 bytes, and I haven't seen anything about the ATT MTU, I'll investigate about it and try it.

Thanks for the help.