UART + non-connectable advertisement

[hmcashan13]

I am trying to broadcast a non-connectable advertisement (such as a beacon) while I am connected to a device that I am transferring data via TX. I am working with a nRF52840 on Segger Embedded Studio v3.4 with the nRF5_SDK_15 as the base for my code manipulation. More specifically I'm going off the ble_app_uart example for pca10040 s132. I don't care about receiving data through RX from the device I am connected to. By the way, I have tried using the Time Slot API where I try to initiate the advertising of the beacon when the device connects through UART. It is my understanding from projects such as the nRF51-multi-role-protocol-conn-observer-advertiser example on github but this is for nrf51 devices. I have tried to mimick this project as well as articles showing how the time slot api can be used to implement non-connectable advertising during a connection as a peripheral. I have also tried doing this without the Time Slot API but to no avail. My thinking is that the buffer transferring data out of the device can only handle 31 bytes of data per interval, but both the advertising and uart protocols take up 31 bytes so its not possible to do at the same time. There must be a way to switch between the two protocols (uart and advertisement) when the radio interrupt occurs. Please help.

[Edvin]

Hello,

When you say: "while I am connected to a device that I am transferring data via TX". Do you mean a physical UART, or UART over BLE (Nordic Uart Service/NUS)?

 

Either way, I don't think you have to use the Timeslot API. You can connect to a device, and start advertising again. You can also start advertising non-connectable while in a connection. All you need to do is to wait for the connected event, set up a non-connectable advertising set (like it is done in the beacon examples), and start advertising again. However, you can't advertise with two advertising sets at the same time. If you want to advertise with the non-connectable advertising at the same time as regular/connectable advertising (for the NUS service), you must manually swap between these, but that is absolutely doable.

 

So do you want to advertise with the non-connectable advertisements while in a BLE connection, or while connected to the physical UART?

 

Best regards,

Edvin

[hmcashan13]

Thanks for getting back Edvin,

I am referring to UART over BLE such as with the ble_app_uart example. What I tried that is pretty much what you are saying. I took the advertising_init and advertising_start methods from the ble_app_uart example and changed their names (advertising_init_beacon and advertising_start_beacon), brought them into the the ble_app_uart example, and when the gap_evt signals that a connection has been initiated, I call the advertising_init_beacon and advertising_start_beacon methods for the beacon in that order. It's failing after I'm calling this method:

sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &m_adv_params);

which is at the end of the advertising_init_beacon method. This is the entire method:

static void advertising_init_beacon(void)
{
    uint32_t      err_code;
    ble_advdata_t advdata;
    uint8_t       flags = BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED;
 
    ble_advdata_manuf_data_t manuf_specific_data;
 
    manuf_specific_data.company_identifier = APP_COMPANY_IDENTIFIER;
 
    manuf_specific_data.data.p_data = (uint8_t *) m_beacon_info;
    manuf_specific_data.data.size   = APP_BEACON_INFO_LENGTH;
 
    // Build and set advertising data.
    memset(&advdata, 0, sizeof(advdata));
 
    advdata.name_type             = BLE_ADVDATA_NO_NAME;
    advdata.flags                 = flags;
    advdata.p_manuf_specific_data = &manuf_specific_data;
 
    // Initialize advertising parameters (used when starting advertising).
    memset(&m_adv_params, 0, sizeof(m_adv_params));
 
    m_adv_params.properties.type = BLE_GAP_ADV_TYPE_NONCONNECTABLE_SCANNABLE_UNDIRECTED;
    m_adv_params.p_peer_addr     = NULL;    // Undirected advertisement.
    m_adv_params.filter_policy   = BLE_GAP_ADV_FP_ANY;
    m_adv_params.interval        = NON_CONNECTABLE_ADV_INTERVAL;
    m_adv_params.duration        = 0;       // Never time out.
 
    err_code = ble_advdata_encode(&advdata, m_adv_data.adv_data.p_data, &m_adv_data.adv_data.len);
    APP_ERROR_CHECK(err_code);

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &m_adv_params);
    APP_ERROR_CHECK(err_code);
}

[Edvin]

What protocol do your sensors use? SPI? UART? TWI/I2C?

BR,

Edvin

[hmcashan13]

I am using an fsr weight sensor (https://www.mouser.com/ProductDetail/SparkFun/SEN-09376?qs=WyAARYrbSnZm3k2OB4XwnA%3D%3D&gclid=Cj0KCQjwlqLdBRCKARIsAPxTGaVJJHUxsem5voGhSz6SU448bj-TSC2OffI2mAEgGkMw_j5pOLybGMsaAjlQEALw_wcB)

and I am using a DS18B20 (https://www.mouser.com/ProductDetail/SparkFun/SEN-11050?qs=WyAARYrbSnY0sq2HamgEvg%3D%3D&gclid=Cj0KCQjwlqLdBRCKARIsAPxTGaVBUMh3fjcHdQMuEvzNDSGc6LQwRu6e9y8JH7MUIWVe5jWGCddBblcaAtpOEALw_wcB)

[Edvin]

Have you found any datasheets for your sensor? You need to know what protocol they use in order to read the data from the sensors.

[hmcashan13]

I don't know what you mean by protocol. I've been going through the data sheets for both the temperature sensor and weight sensor, but neither says anything about protocols. There also aren't any online tutorial for Segger in setting up sensors. I'm attaching links to both the data sheets for the sensors I'm using.

Temp Sensor: http://cdn.sparkfun.com/datasheets/Sensors/Temp/DS18B20.pdf

Weight Sensor: https://cdn-learn.adafruit.com/assets/assets/000/010/126/original/fsrguide.pdf 

[Edvin]

The reason for why there isn't any tutorial for setting up sensors is because different sensors have different protocols. Some use UART, some use I2C, some use SPI, some are analogue (Like your weight sensor), some are something else (Like your Temp sensor. Not standardized). 

The weight sensor uses changes the resistance depending on the weight, so you have to give it some voltage, and measure the voltage drop over the sensor. See the Saadc example on how to do this.

The temp sensor uses a custom protocol. It is called 1-wire-bus. See the datasheet section 1-wire bus system. I don't know what protocol it is, but it looks like a modified SPI or UART, using only one wire (in and output). You will have to experiment a bit with this one, or maybe you can find some tutorials (not from Nordic) on how to use this.

Best regards,

Edvin

[hmcashan13]

So I figured out how to read the sensors using the Saadc example. Now the task that I'm faced with is to relay this data through UART ble_peripheral to my iPhone/Android device. I am using the UART tutorial on ble_peripheral but I'm having a difficult time trying to find out where I pass these values to be sent over UART.

[Edvin]

look for ble_nus_data_send();

It is used in the uart_event_handle() in main.c in that example.

You can use this function to send your data to the phone.

BR,

Edvin

[hmcashan13]

I found what you are referring to and I am able to pass in data properly. What I am having trouble with is being able to call uart_event_handle constantly because the use case is having the bluetooth device emit UART signals in a regular interval with the temp and weight information. I am able to trigger the uart_event_handle by creating a variable of type app_uart_evt_t and passing it into that function. I do this in the main loop, but there is not enough of a delay between each call to this function. My thoughts were to either sleep the thread for a certain period of time which I have had zero success, and I am also trying to create an app_timer to repeatedly call this function in a certain interval but not successfully able to do so. Was wondering if you could help me create this timer or if you could think of a better way. Here is my main loop so far:

for (;;)
    {   
        if(connected == 1) {
              
              
             // create timer
              ret_code_t err_code;
              err_code = app_timer_init();
              APP_ERROR_CHECK(err_code);
              
              // variables to pass into app_timer_create
              app_timer_id_t * timer_id = APP_TIMER_DEF(10);
              app_timer_mode_t * timer_mode = APP_TIMER_MODE_REPEATED;
              app_timer_timeout_handler_t * timer_timeout_handler;
              
              // variable to pass into uart_event_handle
              app_uart_evt_t * p_event;
              // triggers data to be sent over UART
              uart_event_handle(p_event);

              // 
              err_code = app_timer_create(timer_id,timer_mode, timer_timeout_handler);
              APP_ERROR_CHECK(err_code);
        }
        
        idle_state_handle();
    }

But I'm getting a compiler error with the timer_id as I have no idea what to pass in. I also don't think I'm setting the timer_mode variable properly, and I don't know how I can set the timer_timeout_handler to call the part_event_handle function. I've also attached my source code.

[hmcashan13]

2703.ble_app_uart.zip

[Edvin]

Hello,

Sorry for the late reply. I have been out of office this week.

First, I recommend that you do the app_timer_init() outside your main-loop, because in this case you will run app_timer_init() all the time, as long as you are connected, so it will stop and start all the time, and you will create timers just as often, and your app_timer_create() will return NRF_ERROR_INVALID_STATE from the second time it is called.

So move everything that you have inside if(connected == 1){} to before the for(;;)

What you actually don't do is to start the timer, using app_timer_start. This is also something you should do outside your main-loop. If not, you will just start it over and over.

I suspect that the if(connected) part is something you want in your timeout handler. You should initialize your timer in your main() application, before the for (;;) loop, and you can start your timer in the BLE_GAP_EVT_CONNECTED event in ble_evt_handler().

I recommend that you look at the ble_app_hrs example, as this sets up different timers. You can see in the main() function, that it calls timers_init(), application_timers_start().

The m_heart_rate_timer_id is quite similar to what you are trying to achieve. As you can see, the timer_id is defined near the top of main.c, APP_TIMER_DEF(m_heart_rate_timer_id);

If I were to tell you how to do it, it would be a copy paste of the main file from the ble_app_hrs example.

Best regards,

Edvin