Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Tue, 03 Dec 2019 15:09:00 GMT

[quote userid="16704" url="~/f/nordic-q-a/54045/low-transfer-rate-between-nrf52840-dk-ble-and-nrf-connect-android-app/223281"] I only seem to have the problem with Samsung Phones[/quote]

Did you manage to capture a sniffer trace of the problem ?

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Dmitry — Tue, 03 Dec 2019 12:34:57 GMT

It's hard to give you a good help here.. I worked with old android phones with BLE 4.1 and got about 7 kbytes/sec, that was enough for my task. Maybe you could ask matt-lionembedded about his results.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 03 Dec 2019 11:40:26 GMT

What is the transfer rate you manage to achieve ?
Is it against an android phone ?
What GATT settings do you use in the android app ?

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Dmitry — Tue, 03 Dec 2019 11:13:49 GMT

For stream transfers I usually send an asynchronous ACK packet for every 16 input packets, that is also serves as keepalive. Yes, it should be write-without-response.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 03 Dec 2019 10:53:29 GMT

You are right about this (I think) .. I only seem to have the problem with Samsung Phones

How does your keep alive work ?
How often do you send it ? (I try every 100 miliseconds)
What does it contain ? (I send 1 byte)
Where do you send it to ? (I send it to a write_no_resp characteristics)

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Thu, 07 Nov 2019 14:36:55 GMT

[quote user="Atrigen"] I do see it in the scanned devices, but when I connect to it I see the services I have in *my* code[/quote]

The phone has cached the old services. Try to delete the bond on the phone, and connect again. It should then do a new service discovery when it connects.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Thu, 07 Nov 2019 13:57:06 GMT

I tried the example now, here is my take on it:

1. between 2 boards with data_length 251 I get throughput of 1043 Kbps (kilo bit per second). That is about 125 kilo bytes per second - almost twice as fast as I need.

2. When I write "run" with only one board after setting it as tester and attempting to connect to it using nRF Connect. I do see it in the scanned devices, but when I connect to it I see the services I have in *my* code (previously flashed hex). Ie, I dont see any services from the ble_app_att_mtu_throughput code (if there are any). So I have no idea how to test throughput between ble_app_att_mtu_throughput and nRF Connect.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Thu, 07 Nov 2019 12:51:14 GMT

[quote userid="16704" url="~/f/nordic-q-a/54045/low-transfer-rate-between-nrf52840-dk-ble-and-nrf-connect-android-app/219011"]Is it possible for you to post a project code of yours that actually send at rate of 1200 kbps between the DK and the android device ?[/quote]

You can test the throughput using the ble_app_att_mtu_throughput example in the SDK. Remember to increase the data_length to 251. Connect with the phone using nRF Connect for mobile, and enable the notification in the app to start the test. What ATT_MTU and data length you get negotiated with the phone should be printed by the example, and at the end of the test the throughput result is printed.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Thu, 07 Nov 2019 12:31:26 GMT

Unfortunately, the Profile_nRF_Sniffer_v2_001 was not included in the v2 release. But, as e.g indicated in this post, you can find the find and use the files from the previous release (2.0.0_beta3).

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Thu, 07 Nov 2019 11:33:07 GMT

Did you install this sniffer ?

I'm trying to install version 2, but I cant find folder Profile_nRF_Sniffer_v2_001 in the zip file as required in section 2.3.2 (item 5 on the list) in the user guide.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Dmitry — Thu, 07 Nov 2019 11:20:09 GMT

"some time" is milliseconds... a sniffer trace would clarify things a lot

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Thu, 07 Nov 2019 10:25:34 GMT

I lose packets right away, not "after some time".

.. and I get this problem when I connect to the DK with nRF Connect.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Thu, 07 Nov 2019 10:20:54 GMT

1. Changed NRF_SDH_BLE_GATT_MAX_MTU_SIZE to 247 and added the code you suggested between the call to nrf_sdh_ble_default_cfg_set() and the call to nrf_sdh_ble_enable().
2. Updated the .ld file according to the required RAM start location and length that was written in the log.
3. Connected to the DK with nRF connect and changed PHY to LE 2M (TX & RX) + requested connection priority to HIGH.

4. Enabled notification (that makes the DK start sending packets) ... and I lose packets still.

Is it possible for you to post a project code of yours that actually send at rate of 1200 kbps between the DK and the android device ?

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Wed, 06 Nov 2019 15:55:42 GMT

I believe we have seen at least around 1200 kbps on Android.

Note that when the connection event starts, the SoftDevice will empty it's internal buffer as fast as possible by sending the packets to the other device. When the SoftDevice does not have any more packets to send, the connection event is ended, and you will need to wait until the next connection event starts before the SoftDevice sends packets to the peer device(android phone in this case) again.

If possible, I recommend setting the ATT MTU size to 247(NRF_SDH_BLE_GATT_MAX_MTU_SIZE), as this will avoid fragmentation of the ATT packet into several on-air data packets.

You could try to manually increase the TX buffer, and see if it have any effect:

    ble_cfg_t ble_cfg;
    memset(&ble_cfg, 0, sizeof ble_cfg);
    ble_cfg.conn_cfg.conn_cfg_tag           = APP_BLE_CONN_CFG_TAG;
    ble_cfg.conn_cfg.params.gatts_conn_cfg.hvn_tx_queue_size = 50;
    err_code = sd_ble_cfg_set(BLE_CONN_CFG_GATTS, &ble_cfg, ram_start);
    APP_ERROR_CHECK(err_code);

(should be added to ble_stack_init() in main.c )

A sniffer trace could also be useful in analyzing what is happening on-air.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Dmitry — Wed, 06 Nov 2019 15:02:49 GMT

Hi,

maybe you have the same case as this. In short - android device decreases priority of BLE in favor of WiFi link if there is no host activity for some time, solved by sending periodic host-initiated "keepalive" packets.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Wed, 06 Nov 2019 13:16:35 GMT

my configuration is:

#define NRF_SDH_BLE_GATT_MAX_MTU_SIZE 1024 // had to adjust RAM start and length for this
#define NRF_SDH_BLE_GAP_EVENT_LENGTH 352 // was 247, changed to 351, cant see any effect
#define MIN_CONN_INTERVAL MSEC_TO_UNITS(7.5, UNIT_1_25_MS)
#define MAX_CONN_INTERVAL MSEC_TO_UNITS(8, UNIT_1_25_MS)

This is the MTU size I get (in the logs):
<info> app: GATT ATT MTU on connection 0x0 changed to 517.

I added the function and I call it, but the throughput stays the same.

Has anyone ever got a higher transfer rate between an nRF52840-DK and an android device ? (higher than 40 kilo bytes per second)

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Tue, 05 Nov 2019 17:45:16 GMT

I assume that you also have these parameters configured like this:

NRF_SDH_BLE_GATT_MAX_MTU_SIZE 247

NRF_SDH_BLE_GAP_DATA_LENGTH 251

You might also want to enable extended BLE connection events, and see if that improves the throughput.

Create a function like this:

void conn_evt_len_ext_set(void)
{
    ret_code_t err_code;
    ble_opt_t  opt;

    memset(&opt, 0x00, sizeof(opt));
    opt.common_opt.conn_evt_ext.enable = 1;

    err_code = sd_ble_opt_set(BLE_COMMON_OPT_CONN_EVT_EXT, &opt);
    APP_ERROR_CHECK(err_code);
}

and call it after ble_stack_init() in main().

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 05 Nov 2019 17:14:33 GMT

I do that, however it wont fix the core issue that I have:

PDM driver push data faster than I can sent it over BLE. I am bound to hit an overflow somewhere. The only thing I can play with is where the overflow will happen.
In the soft device -> lost packets.
In the PDM handler -> lost PDM buffers.

Only real way to fix this issue is to make it possible for me to send in a transfer rate higher than ~66kbps (kilo bytes per second)

I read a few posts here that people managed to send in much much higher rates, but it isnt clear to me how they did it or if it was ever between a developer board and an android device.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Andy — Tue, 05 Nov 2019 13:57:09 GMT

You can also use the TX done event to retry

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Andy — Tue, 05 Nov 2019 13:40:33 GMT

You have to reorganize your code. Use state machines or the app scheduler or something. You need to be able to retry later in case of error, i.e. fail -> tend to other stuff -> retry again...

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 05 Nov 2019 13:35:15 GMT

didnt see a reply button here to answered above

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 05 Nov 2019 13:34:01 GMT

I've increased NRF_SDH_BLE_GAP_EVENT_LENGTH from 140 (hexadecimal) to 280 (twice the size, didnt know proper value to put there) and I've embedded the sd_ble_gatts_hvx() function inside a do { /* ... */ } while (err_code == NRF_ERROR_RESOURCES); loop.

As a consequence I'm not losing packets over the BLE, however the while loop is stuck for enough time for me to lose buffer(s) passed to me from the PDM handler.

In other words, we moved the problem a stage back in the chain.

The "real" way to handle this is to somehow increase the BLE transfer rate. How do I do that ?

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Andy — Tue, 05 Nov 2019 13:06:13 GMT

You just need to check the error codes returned by sd_ble_gatts_hvx() as Sigurd mentioned.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Sigurd — Tue, 05 Nov 2019 12:59:00 GMT

Are you getting any error codes returned somewhere? E.g. the function sd_ble_gatts_hvx() will return NRF_ERROR_RESOURCES when too many notifications are queued, i.e. the internal SoftDevice buffer is full. If that happens, you will have to queue the packets later.

Try increasing NRF_SDH_BLE_GAP_EVENT_LENGTH in sdk_config.h , it should indirectly increase the SoftDevice buffer size.

RE: Low transfer rate between nRF52840-DK (BLE) and nRF Connect (android app)

Or — Tue, 05 Nov 2019 12:53:15 GMT

What can cause that overwrite ? how can I prevent it ?

Am I trying to send in rate too high somehow ?