Increase max packets

RE: Increase max packets

Alaa — Mon, 04 Mar 2019 10:03:21 GMT

Since I'm using another microcontroller (STM32) that communicates with the Nordic MCU, I eventually solved this by disabling the while loop of send-retry in nordic, and moving the retry process to the STM MCU.

So I disabled the following loop condition:

while (err_code == NRF_ERROR_RESOURCES);

that tries to resend a failed message.

Turns out when the error code is Not Enough Resources (19), the UART is busy, and so I get a HAL_BUSY from HAL_UART_Transmit_IT(). And then I just retry sending the message until it succeeds.

RE: Increase max packets

awneil — Wed, 16 Jan 2019 11:51:51 GMT

Connection interval

MTU size

Use the 2Mbps PHY (BLE 5 High troughput mode)

https://www.nordicsemi.com/Products/Low-power-short-range-wireless/Bluetooth-5

But remember that your Central (especially if it's a phone or tablet) may impose limits ...

RE: Increase max packets

Alaa — Wed, 16 Jan 2019 11:30:26 GMT

Can you tell me what parameters to adjust?

I just tried adding a 500 ms delay after roughly 40 packets, and I'm not getting the error anymore.

RE: Increase max packets

awneil — Wed, 16 Jan 2019 11:27:35 GMT

Arbitrary delays are never a good idea.

Better to look for a specific indication that the link again has capacity.

If you are constantly hitting this, it indicates that you need to re-evaluate something - either send less data, or adjust the link parameters to increase throughput

RE: Increase max packets

Alaa — Wed, 16 Jan 2019 11:16:43 GMT

Thanks for the response,

I verified that the error that I'm getting is NRF_ERROR_RESOURCES.

Regarding the capacity, let's say maximum packets is 40 of size 20. Does that mean that if I send, say 40 packets of size 20, then wait some time, and then continue sending, it will work successfully? How much should the waiting time be?

Thank you

RE: Increase max packets

awneil — Tue, 15 Jan 2019 23:41:46 GMT

You need to investigate to see what happens immediately before the crash.

Maybe you're getting NRF_ERROR_RESOURCES - that sounds a likely candidate, doesn't it?

Instrument your code to see what's happening.

[quote userid="67195" url="~/f/nordic-q-a/42559/increase-max-packets/165831"]if I get this error, what can I do?[/quote]

The link has a finite capacity - you can't just keep chucking data at it over that capacity.

Only you can decide what's appropriate for your application in this situation

just discard excess data?
if the data is "bursty", buffer it somewhere?
tell the STM32 to stop sending data?
compress the data?
decimate the data?
adjust the link parameters to increase throughput?
etc, etc, ...

RE: Increase max packets

Alaa — Tue, 15 Jan 2019 19:31:18 GMT

NUS profile (uart).

To clarify, the crash happens when I send data from microcontroller STM32 to the nordic nrf52 that's connected to it via uart, and then send the data to a smartphone by BLE.

What error should I get? I looked through the error codes (0 to 19) and I can't find anything related to accepting packets.

Also, if I get this error, what can I do?

Here's some of the code inside uart_event_handle() under the case APP_UART_DATA_READY:

do
{
    uint16_t length = (uint16_t)index;
    err_code = ble_nus_string_send(&m_nus, data_array, &length);
    if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_RESOURCES) )
    {
        APP_ERROR_CHECK(err_code);
    }
} while (err_code == NRF_ERROR_RESOURCES);

Or should I be looking somewhere else?

Thanks

RE: Increase max packets

awneil — Tue, 15 Jan 2019 16:03:32 GMT

What BLE profile are you using - eg, NUS?

You should get an error status telling you when the SD can't accept more packets - are you paying attention to that?