NRF52840-DK interface to External BLE Pressure & temperature Sensor

[Vipul2988]

Hi All,

I am new and trying to connect External BLE Pressure Sensor to NRF52840-DK Board

Do you have any example code for interfacing external BLE sensors that I can refer ?

What you suggest to start with .?

[Einar Thorsrud]

Hi,

It is not clear to me if you want to communicate with a sensor device via BLE, or if you have a sensor connected to SPI/TWI or similar, and want to communicate sensor data via BLE. Please elaborate.

[Vipul2988]

Hello,

I want to read third party TDWLB (Transducer Direct LLC) Pressure device value in nRF52840 Board via BLE.

[Einar Thorsrud]

I see. I have no knowledge of the TDWLB myself, but what you need to do is understand how to interface with it. Does id just advertise the data, or do you need a BLE connection? Which (custom?) BLE serivce(s) does it use, and how are they built up? Is that documented in the documentation for the TDWLB? Once you know this, you can get started with implementing what you need on the nRF side.

[Vipul2988]

Hi

I am able to connect that Pressure Sensor with nRF Connect Mobile app and it is advertising Data
See the attachments below for nRF Connect Mobil app.  
There is value of pressure I can See in the nRF Mobile app.
My Question is how can I read these values on nRF52840 DK board and show them on RTT viewer or use for other application 

I will find documents related to this but asking incase we have anything to start with as reference 

[Einar Thorsrud]

Hi,

The screenshot do not show advertisements, but shows that you are connected and are looking at the attribute table (services and characteristics). So to read this from the nRF you would need to implement a GATT client for the service(s) you are interested in that are not implemented in the SDK (for instance non-standard custom services), and use existing implementations for any standard services you need. I suggest you refer to some BLE examples in the SDK (nRF5 SDK or nRF Connect SDK). If you use the nRF5 SDK ad need to implement a custom service, you may also find the Custom Service Tutorial useful.

[Vipul2988]

Thank You for your suggestion, Let me go through those tutorial and links. 

I will update you if any questions will arise. 

[Vipul2988]

Hi Einar,

Here in Custom Service Tutorial, Steps given for creating Custom BLE service in nRF and Read it on Mobile nRF app.

I want to read pressure sensor values in nRF board and want o use it for other application. I have all the UUIDs for that Pressure sensor. 

How can I make custom example in nRF to read those pressure sensor values in nRF -DK board

[Einar Thorsrud]

Hi,

Making your own custom service implementation is demonstrated by the Custom Service Tutorial. I do not think we have any other material that covers this better.

[Vipul2988]

Hi Einar,

I want to use this third party Sensor as peripheral and our nrf52840-DK Board as Central.

We want to read the peripheral sensor value through the BLE connection in our nRF52840-DK Board 

What should I need to look into?

[Einar Thorsrud]

Hi,

You can look at a BLE central example, for instance Nordic UART Service Client, and also see how the NUS client implementation is implemented so use as a reference for implementing your own GATT client (components\ble\ble_services\ble_nus_c\).

[Vipul2988]

Hi Einar,

Before using Nordic UART service Client, I am trying  to pair/connect other device as peripheral to nrf52840 Central.

But it looks like not paring with peripheral device, I looked into Ble_app_Blinky_C example.

Right now I am using nRF5_SDK_17.0.2 with pca10056/S140/SES having nRF52840-DK board

I have changed below things in Main.c

static char const p_target_periph_name[] = "34704" ;

static void scan_init(void)
{
ret_code_t err_code;
nrf_ble_scan_init_t init_cus_scan;

memset(&init_cus_scan, 0, sizeof(init_cus_scan));

init_cus_scan.connect_if_match = true;
init_cus_scan.conn_cfg_tag = APP_BLE_CONN_CFG_TAG;

err_code = nrf_ble_scan_init(&m_scan, &init_cus_scan, scan_evt_handler);
APP_ERROR_CHECK(err_code);

// Setting filters for scanning.
err_code = nrf_ble_scan_filters_enable(&m_scan, NRF_BLE_SCAN_NAME_FILTER, false);
APP_ERROR_CHECK(err_code);

err_code = nrf_ble_scan_filter_set(&m_scan, SCAN_NAME_FILTER, p_target_periph_name);
APP_ERROR_CHECK(err_code);
}

Also Changed #define NRF_BLE_SCAN_NAME_CNT to 1 in sdk_config.h

from here pasted main.c

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/**
* @brief BLE LED Button Service central and client application main file.
*
* This file contains the source code for a sample client application using the LED Button service.
*/

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "nrf_sdh.h"
#include "nrf_sdh_ble.h"
#include "nrf_sdh_soc.h"
#include "nrf_pwr_mgmt.h"
#include "app_timer.h"
#include "boards.h"
#include "bsp.h"
#include "bsp_btn_ble.h"
#include "ble.h"
#include "ble_hci.h"
#include "ble_advertising.h"
#include "ble_conn_params.h"
#include "ble_db_discovery.h"
#include "ble_lbs_c.h"
#include "nrf_ble_gatt.h"
#include "nrf_ble_scan.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

#define CENTRAL_SCANNING_LED BSP_BOARD_LED_0 /**< Scanning LED will be on when the device is scanning. */
#define CENTRAL_CONNECTED_LED BSP_BOARD_LED_1 /**< Connected LED will be on when the device is connected. */
#define LEDBUTTON_LED BSP_BOARD_LED_2 /**< LED to indicate a change of state of the the Button characteristic on the peer. */

#define SCAN_INTERVAL 0x00A0 /**< Determines scan interval in units of 0.625 millisecond. */
#define SCAN_WINDOW 0x0050 /**< Determines scan window in units of 0.625 millisecond. */
#define SCAN_DURATION 0x0000 /**< Timout when scanning. 0x0000 disables timeout. */

#define MIN_CONNECTION_INTERVAL MSEC_TO_UNITS(7.5, UNIT_1_25_MS) /**< Determines minimum connection interval in milliseconds. */
#define MAX_CONNECTION_INTERVAL MSEC_TO_UNITS(30, UNIT_1_25_MS) /**< Determines maximum connection interval in milliseconds. */
#define SLAVE_LATENCY 0 /**< Determines slave latency in terms of connection events. */
#define SUPERVISION_TIMEOUT MSEC_TO_UNITS(4000, UNIT_10_MS) /**< Determines supervision time-out in units of 10 milliseconds. */

#define LEDBUTTON_BUTTON_PIN BSP_BUTTON_0 /**< Button that will write to the LED characteristic of the peer */
#define BUTTON_DETECTION_DELAY APP_TIMER_TICKS(50) /**< Delay from a GPIOTE event until a button is reported as pushed (in number of timer ticks). */

#define APP_BLE_CONN_CFG_TAG 1 /**< A tag identifying the SoftDevice BLE configuration. */
#define APP_BLE_OBSERVER_PRIO 3 /**< Application's BLE observer priority. You shouldn't need to modify this value. */

NRF_BLE_SCAN_DEF(m_scan); /**< Scanning module instance. */
BLE_LBS_C_DEF(m_ble_lbs_c); /**< Main structure used by the LBS client module. */
NRF_BLE_GATT_DEF(m_gatt); /**< GATT module instance. */
BLE_DB_DISCOVERY_DEF(m_db_disc); /**< DB discovery module instance. */
NRF_BLE_GQ_DEF(m_ble_gatt_queue, /**< BLE GATT Queue instance. */
NRF_SDH_BLE_CENTRAL_LINK_COUNT,
NRF_BLE_GQ_QUEUE_SIZE);

//static char const m_target_periph_name[] = "Nordic_Blinky"; /**< "" Name of the device we try to connect to. This name is searched in the scan report data*/
static char const p_target_periph_name[] = "34704"; /**Vipul added new

/**@brief Function to handle asserts in the SoftDevice.
*
* @details This function will be called in case of an assert in the SoftDevice.
*
* @warning This handler is an example only and does not fit a final product. You need to analyze
* how your product is supposed to react in case of Assert.
* @warning On assert from the SoftDevice, the system can only recover on reset.
*
* @param[in] line_num Line number of the failing ASSERT call.
* @param[in] p_file_name File name of the failing ASSERT call.
*/
void assert_nrf_callback(uint16_t line_num, const uint8_t * p_file_name)
{
app_error_handler(0xDEADBEEF, line_num, p_file_name);
}

/**@brief Function for handling the LED Button Service client errors.
*
* @param[in] nrf_error Error code containing information about what went wrong.
*/
static void lbs_error_handler(uint32_t nrf_error)
{
APP_ERROR_HANDLER(nrf_error);
}

/**@brief Function for the LEDs initialization.
*
* @details Initializes all LEDs used by the application.
*/
static void leds_init(void)
{
bsp_board_init(BSP_INIT_LEDS);
}

/**@brief Function to start scanning.
*/
static void scan_start(void)
{
ret_code_t err_code;

err_code = nrf_ble_scan_start(&m_scan);
APP_ERROR_CHECK(err_code);

bsp_board_led_off(CENTRAL_CONNECTED_LED);
bsp_board_led_on(CENTRAL_SCANNING_LED);
}

/**@brief Handles events coming from the LED Button central module.
*/
static void lbs_c_evt_handler(ble_lbs_c_t * p_lbs_c, ble_lbs_c_evt_t * p_lbs_c_evt)
{
switch (p_lbs_c_evt->evt_type)
{
case BLE_LBS_C_EVT_DISCOVERY_COMPLETE:
{
ret_code_t err_code;

err_code = ble_lbs_c_handles_assign(&m_ble_lbs_c,
p_lbs_c_evt->conn_handle,
&p_lbs_c_evt->params.peer_db);
NRF_LOG_INFO("LED Button service discovered on conn_handle 0x%x.", p_lbs_c_evt->conn_handle);

err_code = app_button_enable();
APP_ERROR_CHECK(err_code);

// LED Button service discovered. Enable notification of Button.
err_code = ble_lbs_c_button_notif_enable(p_lbs_c);
APP_ERROR_CHECK(err_code);
} break; // BLE_LBS_C_EVT_DISCOVERY_COMPLETE

case BLE_LBS_C_EVT_BUTTON_NOTIFICATION:
{
NRF_LOG_INFO("Button state changed on peer to 0x%x.", p_lbs_c_evt->params.button.button_state);
if (p_lbs_c_evt->params.button.button_state)
{
bsp_board_led_on(LEDBUTTON_LED);
}
else
{
bsp_board_led_off(LEDBUTTON_LED);
}
} break; // BLE_LBS_C_EVT_BUTTON_NOTIFICATION

default:
// No implementation needed.
break;
}
}

/**@brief Function for handling BLE events.
*
* @param[in] p_ble_evt Bluetooth stack event.
* @param[in] p_context Unused.
*/
static void ble_evt_handler(ble_evt_t const * p_ble_evt, void * p_context)
{
ret_code_t err_code;

// For readability.
ble_gap_evt_t const * p_gap_evt = &p_ble_evt->evt.gap_evt;

switch (p_ble_evt->header.evt_id)
{
// Upon connection, check which peripheral has connected (HR or RSC), initiate DB
// discovery, update LEDs status and resume scanning if necessary. */
case BLE_GAP_EVT_CONNECTED:
{
NRF_LOG_INFO("Connected.");
err_code = ble_lbs_c_handles_assign(&m_ble_lbs_c, p_gap_evt->conn_handle, NULL);
APP_ERROR_CHECK(err_code);

err_code = ble_db_discovery_start(&m_db_disc, p_gap_evt->conn_handle);
APP_ERROR_CHECK(err_code);

// Update LEDs status, and check if we should be looking for more
// peripherals to connect to.
bsp_board_led_on(CENTRAL_CONNECTED_LED);
bsp_board_led_off(CENTRAL_SCANNING_LED);
} break;

// Upon disconnection, reset the connection handle of the peer which disconnected, update
// the LEDs status and start scanning again.
case BLE_GAP_EVT_DISCONNECTED:
{
NRF_LOG_INFO("Disconnected.");
scan_start();
} break;

case BLE_GAP_EVT_TIMEOUT:
{
// We have not specified a timeout for scanning, so only connection attemps can timeout.
if (p_gap_evt->params.timeout.src == BLE_GAP_TIMEOUT_SRC_CONN)
{
NRF_LOG_DEBUG("Connection request timed out.");
}
} break;

case BLE_GAP_EVT_CONN_PARAM_UPDATE_REQUEST:
{
// Accept parameters requested by peer.
err_code = sd_ble_gap_conn_param_update(p_gap_evt->conn_handle,
&p_gap_evt->params.conn_param_update_request.conn_params);
APP_ERROR_CHECK(err_code);
} break;

case BLE_GAP_EVT_PHY_UPDATE_REQUEST:
{
NRF_LOG_DEBUG("PHY update request.");
ble_gap_phys_t const phys =
{
.rx_phys = BLE_GAP_PHY_AUTO,
.tx_phys = BLE_GAP_PHY_AUTO,
};
err_code = sd_ble_gap_phy_update(p_ble_evt->evt.gap_evt.conn_handle, &phys);
APP_ERROR_CHECK(err_code);
} break;

case BLE_GATTC_EVT_TIMEOUT:
{
// Disconnect on GATT Client timeout event.
NRF_LOG_DEBUG("GATT Client Timeout.");
err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gattc_evt.conn_handle,
BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
APP_ERROR_CHECK(err_code);
} break;

case BLE_GATTS_EVT_TIMEOUT:
{
// Disconnect on GATT Server timeout event.
NRF_LOG_DEBUG("GATT Server Timeout.");
err_code = sd_ble_gap_disconnect(p_ble_evt->evt.gatts_evt.conn_handle,
BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
APP_ERROR_CHECK(err_code);
} break;

default:
// No implementation needed.
break;
}
}

/**@brief LED Button client initialization.
*/
static void lbs_c_init(void)
{
ret_code_t err_code;
ble_lbs_c_init_t lbs_c_init_obj;

lbs_c_init_obj.evt_handler = lbs_c_evt_handler;
lbs_c_init_obj.p_gatt_queue = &m_ble_gatt_queue;
lbs_c_init_obj.error_handler = lbs_error_handler;

err_code = ble_lbs_c_init(&m_ble_lbs_c, &lbs_c_init_obj);
APP_ERROR_CHECK(err_code);
}

/**@brief Function for initializing the BLE stack.
*
* @details Initializes the SoftDevice and the BLE event interrupts.
*/
static void ble_stack_init(void)
{
ret_code_t err_code;

err_code = nrf_sdh_enable_request();
APP_ERROR_CHECK(err_code);

// Configure the BLE stack using the default settings.
// Fetch the start address of the application RAM.
uint32_t ram_start = 0;
err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
APP_ERROR_CHECK(err_code);

// Enable BLE stack.
err_code = nrf_sdh_ble_enable(&ram_start);
APP_ERROR_CHECK(err_code);

// Register a handler for BLE events.
NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
}

/**@brief Function for handling events from the button handler module.
*
* @param[in] pin_no The pin that the event applies to.
* @param[in] button_action The button action (press/release).
*/
static void button_event_handler(uint8_t pin_no, uint8_t button_action)
{
ret_code_t err_code;

switch (pin_no)
{
case LEDBUTTON_BUTTON_PIN:
err_code = ble_lbs_led_status_send(&m_ble_lbs_c, button_action);
if (err_code != NRF_SUCCESS &&
err_code != BLE_ERROR_INVALID_CONN_HANDLE &&
err_code != NRF_ERROR_INVALID_STATE)
{
APP_ERROR_CHECK(err_code);
}
if (err_code == NRF_SUCCESS)
{
NRF_LOG_INFO("LBS write LED state %d", button_action);
}
break;

default:
APP_ERROR_HANDLER(pin_no);
break;
}
}

/**@brief Function for handling Scaning events.
*
* @param[in] p_scan_evt Scanning event.
*/
static void scan_evt_handler(scan_evt_t const * p_scan_evt)
{
ret_code_t err_code;

switch(p_scan_evt->scan_evt_id)
{
case NRF_BLE_SCAN_EVT_CONNECTING_ERROR:
err_code = p_scan_evt->params.connecting_err.err_code;
APP_ERROR_CHECK(err_code);
break;
default:
break;
}
}

/**@brief Function for initializing the button handler module.
*/
static void buttons_init(void)
{
ret_code_t err_code;

//The array must be static because a pointer to it will be saved in the button handler module.
static app_button_cfg_t buttons[] =
{
{LEDBUTTON_BUTTON_PIN, false, BUTTON_PULL, button_event_handler}
};

err_code = app_button_init(buttons, ARRAY_SIZE(buttons),
BUTTON_DETECTION_DELAY);
APP_ERROR_CHECK(err_code);
}

/**@brief Function for handling database discovery events.
*
* @details This function is callback function to handle events from the database discovery module.
* Depending on the UUIDs that are discovered, this function should forward the events
* to their respective services.
*
* @param[in] p_event Pointer to the database discovery event.
*/
static void db_disc_handler(ble_db_discovery_evt_t * p_evt)
{
ble_lbs_on_db_disc_evt(&m_ble_lbs_c, p_evt);
}

/**@brief Database discovery initialization.
*/
static void db_discovery_init(void)
{
ble_db_discovery_init_t db_init;

memset(&db_init, 0, sizeof(db_init));

db_init.evt_handler = db_disc_handler;
db_init.p_gatt_queue = &m_ble_gatt_queue;

ret_code_t err_code = ble_db_discovery_init(&db_init);
APP_ERROR_CHECK(err_code);
}

/**@brief Function for initializing the log.
*/
static void log_init(void)
{
ret_code_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);

NRF_LOG_DEFAULT_BACKENDS_INIT();
}

/**@brief Function for initializing the timer.
*/
static void timer_init(void)
{
ret_code_t err_code = app_timer_init();
APP_ERROR_CHECK(err_code);
}

/**@brief Function for initializing the Power manager. */
static void power_management_init(void)
{
ret_code_t err_code;
err_code = nrf_pwr_mgmt_init();
APP_ERROR_CHECK(err_code);
}

static void scan_init(void)
{
ret_code_t err_code;
// nrf_ble_scan_init_t init_scan;
nrf_ble_scan_init_t init_cus_scan;

memset(&init_cus_scan, 0, sizeof(init_cus_scan));

init_cus_scan.connect_if_match = true;
init_cus_scan.conn_cfg_tag = APP_BLE_CONN_CFG_TAG;

err_code = nrf_ble_scan_init(&m_scan, &init_cus_scan, scan_evt_handler);
APP_ERROR_CHECK(err_code);

// Setting filters for scanning.
err_code = nrf_ble_scan_filters_enable(&m_scan, NRF_BLE_SCAN_NAME_FILTER, false);
APP_ERROR_CHECK(err_code);

err_code = nrf_ble_scan_filter_set(&m_scan, SCAN_NAME_FILTER, p_target_periph_name);
APP_ERROR_CHECK(err_code);
}

/**@brief Function for initializing the GATT module.
*/
static void gatt_init(void)
{
ret_code_t err_code = nrf_ble_gatt_init(&m_gatt, NULL);
APP_ERROR_CHECK(err_code);
}

/**@brief Function for handling the idle state (main loop).
*
* @details Handle any pending log operation(s), then sleep until the next event occurs.
*/
static void idle_state_handle(void)
{
NRF_LOG_FLUSH();
nrf_pwr_mgmt_run();
}

int main(void)
{
// Initialize.
log_init();
timer_init();
leds_init();
buttons_init();
power_management_init();
ble_stack_init();
scan_init();
gatt_init();
db_discovery_init();
lbs_c_init();

// Start execution.
NRF_LOG_INFO("Blinky CENTRAL example started.");
scan_start();

// Turn on the LED to signal scanning.
bsp_board_led_on(CENTRAL_SCANNING_LED);

// Enter main loop.
for (;;)
{
idle_state_handle();
}
}