Sending many messages

RE: Sending many messages

Einar Thorsrud — Thu, 06 Jun 2019 13:26:04 GMT

How many packets do you attempt to send each second? BLE bandwidth depends on a number of factors, but generally, you will get higher throughput by trying to send fewer large packets compared to more short packets. Both due to overhead in the BLE link itself, and also due to a limited (but indirectly configurable) number of packet buffers (based on the NRF_SDH_BLE_GAP_DATA_LENGTH and NRF_SDH_BLE_GAP_EVENT_LENGTH parameters).

RE: Sending many messages

firmware_master — Tue, 04 Jun 2019 15:07:24 GMT

I am using the default connection parameters as per the example. I haven't changed anything in the code at all and I am using nRF52832 on both ends. I am using SDK 15.3.0. I do not have a sniffer trace to show this. I am running the example as it is.

RE: Sending many messages

Einar Thorsrud — Tue, 04 Jun 2019 07:50:32 GMT

Hi,

There can be a number of factors controlling this. What about the BLE link?

What connection parameters are used?
Connection interval, packet length, packets per connection event etc?
Do you have a sniffer trace to show this?
Are you using nRF52832 on both ends?
Which SDK version are you using? Which modifications have you made to the example?

RE: Sending many messages

firmware_master — Mon, 03 Jun 2019 14:51:55 GMT

I am using the given example and so I assume that the correct settings have been applied.

I also see this issue when I send 16 & 32 bytes messages for a higher number of messages. So it looks like the FIFO gets filled no matter the size and the bigger size only makes the issue come up earlier.

This is surprising.

WIth a 115200 baud rate, I can sent 11520 bytes per second.

I am sending messages every 10ms so I should be able to send 115.2 or 115 bytes every 10ms. However, I am not able to send even 64, 32 or even 16 bytes. I haven't tried 8 bytes yet.

Thanks

RE: Sending many messages

Einar Thorsrud — Mon, 03 Jun 2019 14:17:56 GMT

Hi,

I want to start with the first question that came to mind: have you started the crystal oscillator? That is generally a good idea when using UART. Failing to do so can result in a too large clock inaccuracy, leading to framing errors.

[quote user=""]I also see that when the transmission stops there is a APP_UART_FIFO_ERROR error at the sender.[/quote]

This could be caused by several things. Have you checked the additional error code in the app_uart_evt_t instance?

[quote user=""]What is the size of the FIFO buffer?[/quote]

That is configured by the second and third parameters in APP_UART_FIFO_INIT().