nRF52 UART connection with constant data stream capability

[Aashay]

Hello, I am working on a project where I have 2 nRF52832 boards with the PCA10040. I have the example developer code examples. I am using the central and peripheral code examples to talk from one UART to another on Tera Term. Although, I noticed that this code is structured so that data is piled in an array and only sent to the other UART when I press "enter" or if it reaches a maximum size (which is very large). I am only using Tera Term to test my boards and not as part of the project. I have an external source of data that works properly on its own and am trying to use these UARTs to establish wireless communication. I have cut the solder bridges SB 22-25 to isolate PO.05 - PO.08 from nRF52832 to the Interface MCU. In pins 6 and 8 on both boards, I put TXD and RXD. Essentially what I am trying to do is have data go though the TXD & RXD wires to one UART, then wirelessly transfer data to the other UART, and have TXD & RXD wires come back. This processes will not work unless the code is structured so that data can be processed (sent & received) continuously. Or at least have it to where whatever is stacked up in the buffer is sent out every interval. I have attached the part of the code for both Central and Peripheral examples that specifically deal with data in UART. I have also put a diagram of sorts to help visualize. Any help would be great. Thanks.

[Vidar Berg]

Hi, you will get higher bandwidth when you split the data into larger chunks as opposed to sending a few bytes at a time (Note: the max data size is defined by m_nus_max_data_len), so it's probably a good idea to accumulate data at a fixed interval before transmitting as you suggested. I would probably have used a longer timer interval though. The lowest connection interval allowed by BT spec. is 7.5 ms anyway. 

Aashay said:

The rest of the data gets lost

 It's not lost by the Softdevice. Data passed to ble_nus_data_send() will be transmitted if the function returns NRF_SUCCESS (i.e., the link will be terminated if a packet is not received within the supervision timeout ). I think it's likely returning NRF_ERROR_RESOURCES as it's easier to fill the Softdevice's TX buffer when you send many small notifications rather than few large notifications. The message for handle value notification illustrates this: https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s132.api.v6.1.1/group___b_l_e___g_a_t_t_s___h_v_n___m_s_c.html?cp=3_4_1_1_2_4_3_5 

I'd recommend using an app timer instance to control the data transfer. You can use the ble_app_hrs example to see how timers are initialized. 

[Aashay]

Hi, I looked at the ble_app_hrs example. I am still having trouble trying to incorporate a timer instance. If I could get some assistance on what to do, it would be awesome.

[Vidar Berg]

Hi, I thought you used Segger embedded Studio so that's what I used. Please try with the two projects I uploaded. It would be a bit time consuming to repeat the process and add all of the required source files and include paths to Keil.  

[Aashay]

Hey Vidar Berg, sorry I should have mentioned that I was using Keil. Regardless, I was able to compile it successfully on segger embedded. I just have some questions on how to alter the code to change what the buttons and leds do.

I wanted the whole process to look like this:

Once the boards turn on, LED1 is off. When BUTTON1 is pressed, it initiates the pairing process (to search for link) on that board. and cant connect unless another board is also in the same searching process. In this process I want the LED1 to be blinking. Once the boards are connected, the LED1 stays on. I want BUTTON2 to be able to completely terminate the link and make the LED1 turn off. And to reconnect, we would repeat the process. 

Is this possible? And where would this be coded/how could it be done?

Thanks so much for all the help.

[Aashay]

Also, for the BUTTON2, how could make it so that user has to hold BUTTON2 for at least 3 seconds to terminate connection or else nothing happens. (app timer maybe?)

[Aashay]

Vidar Berg

[Vidar Berg]

Please take a look at my answer in this thread for suggestions on how to detect a long button press.