How to change from BLE central to peripheral mode by buttons

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Wed, 28 Dec 2016 11:20:16 GMT

Here is a project which use UART/printf instead of NRF_LOG: ble_app_hrs_nus_printf.zip. If you are only using NUS, you should use combine the ble_app_uart and ble_app_uart_c applications to have both peripheral and central with UART communication.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Sat, 24 Dec 2016 20:22:56 GMT

Yes, I tried the instruction that you gave me with the NRF_LOG_ENABLED 0 and the RETARGET_ENABLED 1, but then when I run the code and observe the terminal, there were no words and it is blank meaning that it is not printing correctly. Also, put printf() on the main.c code instead of NRF_LOG_INFO Is there anything else that I need to do? Do you think if I don't use the heart rate service in the future, which example from the ones that you provided in the SDK is suitable? As I said before, I need something that is able to have UART communication as well have a user application that can have both central and peripheral. Thanks.

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Thu, 22 Dec 2016 11:36:55 GMT

If you are not planning to connect any devices that is running the heart rate service, it would just be waste of space and resources to have code that handles this on the device, but if you are planning to connect such devices in the future, this should be OK. You can call uart_init(), just not if you have NRF_LOG with UART backend enabled. If you disable the logging module (set NRF_LOG_ENABLED 0 in sdk_config.h) and adds #define RETARGET_ENABLED 1 in the same file, you can call uart_init() and use printf() in place of NRF_LOG_INFO() for UART logging.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Wed, 21 Dec 2016 17:29:42 GMT

Basically, my application is used to connect to both central and/or peripheral devices.I am using a single central code which is the HRS example with some modifications because I thought it would be easier since it already had the central and peripheral implementation. However, for my application, there needs to be UART service implemented for which there is a central UART terminal which will send data to the peripheral UART terminal through the user application. This is why I used the UART example that was provided and was trying to combine both UART and the HRS example. Currently I do not have any heart rate devices but other devices such as GoPro that I want to connect. Is this alright to do or do we need to handle it in a different way?

UPDATE: Also wanted to ask how I can use the uart_event_handle() in the HRS example? It contains the necessary function ble_nus_c_string_send which would allow the user to send information through UART. It is because in the UART example, it is called in the uart_init() method which cannot be used for the HRS example like you described.

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Wed, 21 Dec 2016 15:35:48 GMT

Yes. Are you trying to create an application that can either connect to HRS devices or to NUS devices? Typically it would be more convenient to create a single central code and handle the different services when discovered. If you want to handle both services on a device, you might have to handle this in another way.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Wed, 21 Dec 2016 15:08:31 GMT

Thank you for the response. How about the discovery handler, should I do the similar process to the dispatch as you suggested and add the method call inside the db_disc_handler(ble_db_discovery_evt_t * p_evt) in the HRS example?

static void db_disc_handler(ble_db_discovery_evt_t * p_evt)

    ble_hrs_on_db_disc_evt(&m_ble_hrs_c, p_evt);
}

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Tue, 20 Dec 2016 09:42:13 GMT

You should dispatch all the ble events inside the same ble_evt_dispatch() function, not in two separate functions. Just add ble_nus_c_on_ble_evt(&m_ble_nus_c,p_ble_evt) inside ble_evt_dispatch() in the HRS example.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Mon, 19 Dec 2016 18:11:09 GMT

Thank you I have successfully fixed the L6218E errors. Last question, as I was observing the ble_app_uart_c I noticed some of the methods in that example code which are not included in my code. Is it neccessary to another ble_evt_dispatch method for the calling of &m_ble_nus_c. Currently there is another dispatch for &m_hrs.

For example:

From the ble_app_uart example

static void ble_evt_dispatch(ble_evt_t * p_ble_evt)
{
    on_ble_evt(p_ble_evt);
    bsp_btn_ble_on_ble_evt(p_ble_evt);
    ble_db_discovery_on_ble_evt(&m_ble_db_discovery, p_ble_evt);
    **ble_nus_c_on_ble_evt(&m_ble_nus_c,p_ble_evt);**
}

From the BLE hrs_multi example

static void ble_evt_dispatch(ble_evt_t * p_ble_evt)

{
    uint16_t conn_handle;
    uint16_t role;

    ble_conn_state_on_ble_evt(p_ble_evt);
    pm_on_ble_evt(p_ble_evt);

    // The connection handle should really be retrievable for any event type.
    conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
    role        = ble_conn_state_role(conn_handle);

    // Based on the role this device plays in the connection, dispatch to the right applications.
    if (role == BLE_GAP_ROLE_PERIPH)
    {
        // Manages peripheral LEDs.
        on_ble_peripheral_evt(p_ble_evt);

        ble_advertising_on_ble_evt(p_ble_evt);
        ble_conn_params_on_ble_evt(p_ble_evt);

        // Dispatch to peripheral applications.
        **ble_hrs_on_ble_evt (&m_hrs, p_ble_evt);**
.......
}

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Mon, 19 Dec 2016 17:10:15 GMT

If you get L6218E errors, you either have not included the correct source file, or have not enabled the module in the SDK configuation header file. I looked through you code and see that you are calling nus_c_init() before ble_stack_init(). nus_c_init() contains calls to softdevice functions, so calling this before enabling the softdevice/bluetooth stack will lead to an error. I'm not sure if you have enabled the NRF_LOG module in the SDK configuration header, but if you have, you should not call uart_init(). This will lead to the hardware UART interface being initialized two times. I recommend to use the NRF_LOG module. I attached a working Keil project containing your code and my fixes: ble_app_hrs_nus.zip

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Mon, 19 Dec 2016 14:19:17 GMT

Thank you that is what I have done. However, when I flashed the code in the NRF52 board and checked in the UART terminal, it would give me a APP_ERROR:ERROR:Fatal when attempting to have a UART service as we discussed before. I was not sure why though.

Should I keep the m_ble_nus_c and the m_ble_hrs_c variables because I am trying to implement the m_ble_nus_c similar to the UART example that you have provided, but still implement it within the heart rate example?

UPDATE: The line number for the error code is 0x6508, the p_file_name is 0x000281D5, and the error code is 0x00000106.

Here is what I have so far if you wanted to take a look at it. gist.github.com/.../26f0a96596d019c414d641fe2c5a157f

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Mon, 19 Dec 2016 09:20:08 GMT

Is the file not added when you try to add it to the Keil project? If you are using SDK 12.x, you also have to enable the module in the SDK configuration header, by setting #define APP_UART_ENABLED 1.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Fri, 16 Dec 2016 16:11:27 GMT

Thanks for you help. When I was implementing the UART example and attempted to compile the main.c file, there was an error L6218E. I was trying to import the libraries such as the app_uart_fifo.c to the project that I have but it doesn't allow me to do that even when I right clicked to on the project tab and tried to add the existing files. Any ideas?

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Fri, 16 Dec 2016 15:29:19 GMT

You have to study the ble_app_uart example. The handler function should could be implemented in main.c or any other file you see fit. Have a look at the nus_data_handler() function in the example. nrf_drv_uart.c is used for controlling the hardware UART interface, it has nothing to do with BLE NUS. What you are looking for is propably ble_nus.h/c, which can be found in [SDK_ROOT]\components\ble\ble_services.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Fri, 16 Dec 2016 14:47:21 GMT

Ok I will add it to the GATT table. Where should I add the handler functions? Would it be in the main.c file? Also, I noticed that there is a nrf_drv_uart.c driver file that came with the SDK. Do you think I can utilize that?

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Fri, 16 Dec 2016 14:37:51 GMT

This should not be a problem, you just have to add the relevant service/characteristics to the GATT table in the relay example, and add the corresponding handler functions.

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Fri, 16 Dec 2016 14:33:01 GMT

Nordic UART Service over BLE but I wanted to implement with the BLE relay example. The reason is that I want to create an application where central can connect to any peripherals and also the central can transmit data to any peripheral device.

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Fri, 16 Dec 2016 14:28:37 GMT

Hardware UART or Nordic UART Service/UART emulation over BLE?

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Fri, 16 Dec 2016 14:15:44 GMT

Thank you for you answer. It really helped. Also, do you think there is a way to implement UART for the BLE relay example?

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Thu, 15 Dec 2016 10:31:10 GMT

It should be possible, but we don't have any examples showing this. You will have to initialize buttons in main, and do all initialization of the program you want to run, and shutdown of the currently running program, in the button event handler (you can also use a flag and do initialization in main based on the set flag). I attached pseudocode to show principle:

enum OP_MODE {INIT,CENTRAL,PERIPHERAL);
OP_MODE mode = INIT;

button_event_handler()
{
	switch (button_evt)
	case BUTTON_0: //Switch to Central mode
		if(mode == PERIPHERAL)
		{
			advertising_stop();
		}
		init_central();
		start_scan();
		mode = CENTRAL;
	break;
	
	case BUTTON_1: //Switch to Peripheral mode
		if(mode == CENTAL)
		{
			scan_stop();
		}
		init_peripheral();
		advertising_start();
		mode = PERIPHERAL;
	break;
	
	case BUTTON_2: //Turn off both modes
		if(mode == CENTAL)
		{
			advertising_stop();
		}
		else if(mode == PERIPHERAL)
		{
			scan_stop();
		}
		mode = INIT;
	break;
	
	default:
	break;
}

main()
{
	buttons_init();
	ble_stack_init();
	while(1)
	{
		sd_app_evt_wait();
	}
}

RE: How to change from BLE central to peripheral mode by buttons

Jimmy — Wed, 14 Dec 2016 15:50:01 GMT

Hi, thanks for your response. Do you know if there is a way that I can run an example code for each button that I press. For example, for button 1, is there a way to run the Central mode connection example that you provided and for button 2 have a peripheral mode example code run. I wasn't sure how to do that in the BLE Relay example. I know that I have to call the button_handler method, but I was not sure how to move forward from that. Please let me know if you have any questions.

RE: How to change from BLE central to peripheral mode by buttons

Jørgen Holmefjord — Tue, 13 Dec 2016 11:37:45 GMT

Hi,

The S130 (nRF51) and S132 (nRF52) softdevices are capable of running concurrently in peripheral and central mode with up to 8 individual links (up to 20 in latest S132 v4.0.0 alpha release). You are therefore not required to switch from central to peripheral mode and back, but you can of course do this if you want to. It is also possible to configure button presses to start advertising/scanning for a predefined period of time if this is what you want.

I recommand that you take a look at the BLE Relay example and the BLE LE Secure Connections multirole example, which both use concurrent paripheral and central mode.

Best regards,

Jørgen

RE: How to change from BLE central to peripheral mode by buttons

awneil — Tue, 13 Dec 2016 08:01:42 GMT

You have 2 entirely separate and unrelated things here:

Detecting button presses;
Switching between Central & Peripheral modes.

So which one do you actually require the help with?