ble_uart demo throughput is very slow

RE: ble_uart demo throughput is very slow

Petter Myhre — Thu, 20 Oct 2016 11:45:40 GMT

Great to hear :)

RE: ble_uart demo throughput is very slow

Nomados — Thu, 20 Oct 2016 00:07:02 GMT

Wow, much better... Thank you! It works without jerks and also much faster. I think NRF BLE-uart example should me updated with your code!

RE: ble_uart demo throughput is very slow

Petter Myhre — Wed, 19 Oct 2016 14:51:38 GMT

I tested your code. I think it is actually your UART baudrate of 19200 that is limiting the throughput here.

I tried to increase the baudrate to 115200, and then ble_nus_string_send() was called frequently enought to get the BLE_ERROR_NO_TX_BUFFERS error.

To handle this a had to make quite a few changes to the project. The unmodifed example doesn't really handle overflow from UART. Please find my modified project here. It was made for S110 v8.0.0 and SD 10.0.0. Unzip it in examples\ble_peripheral\ It is not well tested.

With a connection interval of 39 (48.75ms) I got 2kB/s with 115200, and 1577B/s with 19200.

With a connection interval of 12 (15ms) I got 4kB/s with 115200. You can decrease the connection interval by using nRF Connect for Android, when you have connected click on the vertical ... and select request connection priority, use connection priority high.

RE: ble_uart demo throughput is very slow

Nomados — Tue, 18 Oct 2016 07:21:37 GMT

It is almost the same, I just added printf for changed connection interval in BLE_EVT_TX_COMPLETE: http://pastebin.ru/7d5NSTEs

RE: ble_uart demo throughput is very slow

Petter Myhre — Mon, 17 Oct 2016 07:51:45 GMT

Ok. I can also test your firmware with a smart phone that I know supports more packets per connection interval, if you want. Then please upload it.

RE: ble_uart demo throughput is very slow

Nomados — Fri, 14 Oct 2016 00:03:48 GMT

OK, I have tested with Samsung Galaxy S3 (Android 4.4.4). It has absolutely the same pattern - initially 2-3 packets per interval but after some time it slows down and goes with jerks printing 1.

RE: ble_uart demo throughput is very slow

Nomados — Thu, 13 Oct 2016 23:13:22 GMT

Now I have Chinese ZTE Nubia Z7 Max running Android 5.1.1. But other smartphones showed the same performance. I will report today.

RE: ble_uart demo throughput is very slow

Petter Myhre — Thu, 13 Oct 2016 08:06:00 GMT

Which smart phone have you tested with?

RE: ble_uart demo throughput is very slow

Nomados — Thu, 13 Oct 2016 07:51:29 GMT

OK, I will try with old Galaxy S2 and report the results.

RE: ble_uart demo throughput is very slow

Petter Myhre — Thu, 13 Oct 2016 07:14:29 GMT

Ok. Then it seems that the smart phone is limiting the bandwidth. Do you have any other smart phones to test with?

RE: ble_uart demo throughput is very slow

Nomados — Thu, 13 Oct 2016 06:45:40 GMT

I added this event handler to static void on_ble_evt(ble_evt_t * p_ble_evt) function.

  case BLE_EVT_TX_COMPLETE:
printf("TX count per interval %d\n",  p_ble_evt->evt.common_evt.params.tx_complete.count);
app_uart_evt_t fake_evt;
fake_evt.evt_type = APP_UART_DATA_READY;
uart_event_handle(&fake_evt);
break;

And it always prints 1.

When I encreased the interval upto 20 it prints like 2-3 initially and thus works quite fast. But after some time I got almost exlusively 1 and it starts to transmite with jerks. I suppose the reason is inside the softdevice... Should I try other SDs?

RE: ble_uart demo throughput is very slow

Petter Myhre — Wed, 12 Oct 2016 10:35:04 GMT

Ok. Then you have the smallest possible connection interval, 7.5ms. It seems you are correctly calling ble_nus_string_send() until you get BLE_ERROR_NO_TX_BUFFERS. You should start calling ble_nus_string_send() again when get the BLE_EVT_TX_COMPLETE event. When you get this event you should also check p_ble_evt->evt.common_evt.params.tx_complete.count; This will tell you how many packets that were transmitted in the last connection interval.

RE: ble_uart demo throughput is very slow

Nomados — Tue, 11 Oct 2016 23:20:56 GMT

Hello Petter, Sorry, it was my blunder. Now it prints

Max interval 6
Min interval 6

But in this case I am wondering why is it so slow? Sending a small chunk of data is quite brisk, but if it is more than several hundred bytes it slows down and data is transferring with jerks.

RE: ble_uart demo throughput is very slow

Petter Myhre — Tue, 11 Oct 2016 08:02:08 GMT

In the code you sent me you are still printing

p_ble_evt->evt.gap_evt.params.connected.conn_params.max_conn_interval
p_ble_evt->evt.gap_evt.params.connected.conn_params.min_conn_interval

when you get the BLE_GAP_EVT_CONN_PARAM_UPDATE please print:

p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.max_conn_interval
p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.min_conn_interval

RE: ble_uart demo throughput is very slow

Nomados — Tue, 11 Oct 2016 00:42:43 GMT

Sorry for the late reply. I had some personal issues. I use SDK10 and softdevice S110 (modifed periferal example) Here is the code

RE: ble_uart demo throughput is very slow

Petter Myhre — Fri, 07 Oct 2016 08:07:21 GMT

Strange. I would like to try to reproduce this. Could you edit your question and upload your complete project? So I can test it here. What SDK and SoftDevice version are you using?

RE: ble_uart demo throughput is very slow

Nomados — Fri, 07 Oct 2016 06:18:19 GMT

I got 14 and 9 for this. They are still different

RE: ble_uart demo throughput is very slow

Petter Myhre — Fri, 07 Oct 2016 06:13:23 GMT

Use:

p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.max_conn_interval
p_ble_evt->evt.gap_evt.params.conn_param_update.conn_params.min_conn_interval

RE: ble_uart demo throughput is very slow

Nomados — Fri, 07 Oct 2016 05:59:09 GMT

They are different... I just have extended the case expression of on_ble_evt(...) function

  case BLE_GAP_EVT_CONN_PARAM_UPDATE:
      printf("Max interval %d\n",  p_ble_evt->evt.gap_evt.params.connected.conn_params.max_conn_interval);
      printf("Min interval %d\n",  p_ble_evt->evt.gap_evt.params.connected.conn_params.min_conn_interval);
      break;

RE: ble_uart demo throughput is very slow

Petter Myhre — Fri, 07 Oct 2016 05:53:45 GMT

When you get the BLE_GAP_EVT_CONN_PARAM_UPDATE event the max and min should be equal, could you check again? The limitation is on the smart phone, so switching peripheral hardware wouldn't really help.

RE: ble_uart demo throughput is very slow

Nomados — Fri, 07 Oct 2016 00:33:40 GMT

I have added the BLE_GAP_EVT_CONN_PARAM_UPDATE event handler and got these results: Max interval 11 Min interval 9 So, it turned out that the Android OS agreed to decrease these intervals. I carefully measured the transfer rate and it was around 1Kbyte/s or slightly less. Maybe I should consider migration to Bluetooth 4.2 HW, which allows bigger packet size? Having 1Kb/s today sounds ridiculous nowadays :)

RE: ble_uart demo throughput is very slow

Petter Myhre — Thu, 06 Oct 2016 13:03:48 GMT

Ok. It is in 1.25 ms units, so when you connect you have a connection interval of 48.75 ms. You can try to decrease the connection interval by sending a connection parameter update(CPU) request, but the central can reject it. I'm guessing that you already have included the connection parameter module, it will send a CPU request 5 seconds after connection is establised. It will send the CPU request with the MIN_CONN_INTERVAL and MAX_CONN_INTERVAL values defined in main.c Then you can check the BLE_GAP_EVT_CONN_PARAM_UPDATE event if the actual connection interval changed or not. See this MSC for more information. You can find the small connection interval by trying and failing.

RE: ble_uart demo throughput is very slow

Nomados — Thu, 06 Oct 2016 04:20:34 GMT

Hello. I added this lines to the event handler:

case BLE_GAP_EVT_CONNECTED:
            err_code = bsp_indication_set(BSP_INDICATE_CONNECTED);
            APP_ERROR_CHECK(err_code);
            m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
            // Check connection interval
            printf("Max interval %d\n",  p_ble_evt->evt.gap_evt.params.connected.conn_params.max_conn_interval);
            printf("Min interval %d\n",  p_ble_evt->evt.gap_evt.params.connected.conn_params.min_conn_interval);

And I got 39 for both. It gives me around 500 bytes per second. Maybe I can decrease this interval in the Android side? How should I modify nRF UART app?

Also I have modifed sending part (APP_UART_DATA_READY event) from UART to BLE according to your advice, but this did not improve speed, but the FW stability was better.

RE: ble_uart demo throughput is very slow

Petter Myhre — Wed, 05 Oct 2016 08:16:20 GMT

The central device dictates the connection interval, could you check what the actual connection interval is? How is described here. Maybe you could also provide a sniffer trace? You can use nRF Sniffer. How to send large amounts of data is described here.

RE: ble_uart demo throughput is very slow

Nomados — Tue, 04 Oct 2016 23:56:00 GMT

Well, I use an Android phone and nRF UART App. I have connected my BL600 to serial port with 19200 bps with HW flow control, but the NUS speed is too slow to catch up with serial. I use Putty and just put some text to be sent to the phone. According to my measurements it is around 700 bytes per sec, which is really far from your theoretical limit. I tried to minimize connection interval details, but this did not help much. MIN_CONN_INTERVAL = 7.5 MAX_CONN_INTERVAL = 8 I also have tried to increase the buffer sizes UART_TX_BUF_SIZE = 1024 and UART_RX_BUF_SIZE = 1024 Transmission of 8Kb data chunk starts with jerks, then speeds up and continues with long pauses (up to 3 seconds). That's why I am asking your support team to analyze this trivial case and provide some additional example for maximum throughput and minimum delays. Thank you in advance.

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