Gas sensor reading and passing over ble to Android

[Mostafa]

Hello,

I'm a beginner in Nordic ble.

I explain my question as following:

Currently, I'm using a platform integrating several ambient and motion sensors(Temperature, Air pressure, Humidity, Acc, Mag. and Gyres.) these sensors are already integrated and communicating through I2C to the Nrf51. I have to add some gas sensors(CO,CO2and...) which output is a voltage and analogue and has to be connected to ADC pin in Nrf518122 and then passing the data over ble to Android to be monitored.

can I use Ble_proximity sample code in examples which also sounds is a connected to ADC?

If so, how and where to change the code?

How can I make match the data transferring from ADC and other already integrated sensors over the BLe to not interfere.

Please, maybe this question does not make sense for many of you, but I'm a beginner:)

Any further tips and guidance are welcomed.

Best regards, Mostafa.

[Hung Bui]

Hi Mostafa,

The ble_app_proximity use ADC to measure the battery level and send it over BLE. You can have a look at the example to know how to use the ADC (we also have example for the ADC only).

My suggestion is to get familiar with BLE and how it works with our Softdevice and in the examples in our SDK. I would suggest to have a look at the ble_app_blinky example, we also have an Android app for it, here.

Note that it's doesn't mater what kind of data you want to collect, when you send the data via BLE, it will be (and should be) send as an array of byte.

[Mostafa]

MyZip (1).zipHi Bung,

Thanks for the answer. Please allow me to redefine my question in this way because I think my previous one was incomplete. -I'm supposed to use 4 gas sensors(or maybe 5 sensors), but not simultaneously. Fortunately, each sensor has a enable pin which can be set up independently. Now, I explain the procedure, then will ask the point. I'm going to divide every 1 minute to 4 parts each 15 seconds, it means, enable each sensor for 15 seconds. In this way I always have only one sensor running and one input in ADC pin to be read.(right?) Therefore I need to configure the ADC pin to read only one input and I think it does not mind which sensor it would be.(all sensor'S output all analog voltage-but I'm not sure how large the range of variation is, but all are from the same family) not the point is that, as there are different conversions for each sensor to dedicate the measurement according to ppm(gas measurement) for each reading, can I do this in the main function? For instance, I assign, if the pin 2 is enabled then this type of conversion is applied? And would you think this conversion is better to be done in µcontroller side and then pass the value over the ble-uart or Android application side(sending the raw data over ble and then conversion is performed in Android part-is it possible)?

and please, if possible address me to a full complete example with all library. Best regards, thanks for being patient. Mostafa.

[Hung Bui]

You need to make sure the sensor switch its output to high impedance when it's not active. This way you can connect their output together to single pin. It's better to separate them to avoid interference.

I don't see any problem with your set-up.

What do you mean by "full complete example with all library" ? I don't think we have something exactly the same as what you want. What we have is BLE example with ADC code. And you should start from there.

[Mostafa]

Thnaks for the comment. this is ble_uart code for ADc, I think i can use it for my project with the least edition, isn't it? /* Copyright (c) 2014 Nordic Semiconductor. All Rights Reserved. *

• The information contained herein is property of Nordic Semiconductor ASA.
• Terms and conditions of usage are described in detail in NORDIC
• SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
• Licensees are granted free, non-transferable use of the information. NO
• WARRANTY of ANY KIND is provided. This heading must NOT be removed from
• the file.

*/

/** @file *

• @defgroup ble_sdk_uart_over_ble_main main.c
• @{
• @ingroup ble_sdk_app_nus_eval
• @brief UART over BLE application main file.
• This file contains the source code for a sample application that uses the Nordic UART service.
• This application uses the @ref srvlib_conn_params module. */

#include <stdint.h> #include <string.h> #include "nordic_common.h" #include "nrf.h" #include "ble_hci.h" #include "ble_advdata.h" #include "ble_advertising.h" #include "ble_conn_params.h" #include "softdevice_handler.h" #include "app_timer.h" #include "app_button.h" #include "ble_nus.h" #include "app_uart.h" #include "app_util_platform.h" #include "bsp.h" #include "bsp_btn_ble.h" #include "nrf_drv_adc.h" #include "nrf_delay.h"

#define IS_SRVC_CHANGED_CHARACT_PRESENT 0 /**< Include the service_changed characteristic. If not enabled, the server's database cannot be changed for the lifetime of the device. */

#define CENTRAL_LINK_COUNT 0 /*< Number of central links used by the application. When changing this number remember to adjust the RAM settings/ #define PERIPHERAL_LINK_COUNT 1 /*< Number of peripheral links used by the application. When changing this number remember to adjust the RAM settings/

#define DEVICE_NAME "Nordic_UART" /< Name of device. Will be included in the advertising data. */ #define NUS_SERVICE_UUID_TYPE BLE_UUID_TYPE_VENDOR_BEGIN /< UUID type for the Nordic UART Service (vendor specific). */

#define APP_ADV_INTERVAL 64 /< The advertising interval (in units of 0.625 ms. This value corresponds to 40 ms). */ #define APP_ADV_TIMEOUT_IN_SECONDS 180 /< The advertising timeout (in units of seconds). */

#define APP_TIMER_PRESCALER 0 /< Value of the RTC1 PRESCALER register. */ #define APP_TIMER_OP_QUEUE_SIZE 4 /< Size of timer operation queues. */

#define MIN_CONN_INTERVAL MSEC_TO_UNITS(20, UNIT_1_25_MS) /< Minimum acceptable connection interval (20 ms), Connection interval uses 1.25 ms units. */ #define MAX_CONN_INTERVAL MSEC_TO_UNITS(75, UNIT_1_25_MS) /< Maximum acceptable connection interval (75 ms), Connection interval uses 1.25 ms units. */ #define SLAVE_LATENCY 0 /< Slave latency. */ #define CONN_SUP_TIMEOUT MSEC_TO_UNITS(4000, UNIT_10_MS) /< Connection supervisory timeout (4 seconds), Supervision Timeout uses 10 ms units. */ #define FIRST_CONN_PARAMS_UPDATE_DELAY APP_TIMER_TICKS(5000, APP_TIMER_PRESCALER) /< Time from initiating event (connect or start of notification) to first time sd_ble_gap_conn_param_update is called (5 seconds). */ #define NEXT_CONN_PARAMS_UPDATE_DELAY APP_TIMER_TICKS(30000, APP_TIMER_PRESCALER) /< Time between each call to sd_ble_gap_conn_param_update after the first call (30 seconds). */ #define MAX_CONN_PARAMS_UPDATE_COUNT 3 /**< Number of attempts before giving up the connection parameter negotiation. */

#define DEAD_BEEF 0xDEADBEEF /**< Value used as error code on stack dump, can be used to identify stack location on stack unwind. */

#define UART_TX_BUF_SIZE 256 /< UART TX buffer size. */ #define UART_RX_BUF_SIZE 256 /< UART RX buffer size. */

#define ADC_BUFFER_SIZE 4 /< Size of buffer for ADC samples. */ static nrf_adc_value_t adc_buffer[ADC_BUFFER_SIZE]; /< ADC buffer. */ static nrf_drv_adc_channel_t m_channel_config = NRF_DRV_ADC_DEFAULT_CHANNEL(NRF_ADC_CONFIG_INPUT_2); /**< Channel instance. Default configuration used. */ static uint8_t adc_event_counter = 0;

static ble_nus_t m_nus; /< Structure to identify the Nordic UART Service. */ static uint16_t m_conn_handle = BLE_CONN_HANDLE_INVALID; /< Handle of the current connection. */

static ble_uuid_t m_adv_uuids[] = {{BLE_UUID_NUS_SERVICE, NUS_SERVICE_UUID_TYPE}}; /**< Universally unique service identifier. */

/**@brief Function for assert macro callback. *

• @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 analyse

•      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(DEAD_BEEF, line_num, p_file_name); }

/**@brief Function for the GAP initialization. *

• @details This function will set up all the necessary GAP (Generic Access Profile) parameters of

•      the device. It also sets the permissions and appearance.
  

*/ static void gap_params_init(void) { uint32_t err_code; ble_gap_conn_params_t gap_conn_params; ble_gap_conn_sec_mode_t sec_mode;

BLE_GAP_CONN_SEC_MODE_SET_OPEN(&sec_mode);

err_code = sd_ble_gap_device_name_set(&sec_mode,
                                      (const uint8_t *) DEVICE_NAME,
                                      strlen(DEVICE_NAME));
APP_ERROR_CHECK(err_code);

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

gap_conn_params.min_conn_interval = MIN_CONN_INTERVAL;
gap_conn_params.max_conn_interval = MAX_CONN_INTERVAL;
gap_conn_params.slave_latency     = SLAVE_LATENCY;
gap_conn_params.conn_sup_timeout  = CONN_SUP_TIMEOUT;

err_code = sd_ble_gap_ppcp_set(&gap_conn_params);
APP_ERROR_CHECK(err_code);

}

/**@brief Function for handling the data from the Nordic UART Service. *

• @details This function will process the data received from the Nordic UART BLE Service and send

•      it to the UART module.
  

• @param[in] p_nus Nordic UART Service structure.
• @param[in] p_data Data to be send to UART module.
• @param[in] length Length of the data. */ /@snippet [Handling the data received over BLE] */ static void nus_data_handler(ble_nus_t * p_nus, uint8_t * p_data, uint16_t length) { for (uint32_t i = 0; i < length; i++) { while(app_uart_put(p_data[i]) != NRF_SUCCESS); } while(app_uart_put('\n') != NRF_SUCCESS); } /@snippet [Handling the data received over BLE] */

/**@brief Function for initializing services that will be used by the application. */ static void services_init(void) { uint32_t err_code; ble_nus_init_t nus_init;

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

nus_init.data_handler = nus_data_handler;

err_code = ble_nus_init(&m_nus, &nus_init);
APP_ERROR_CHECK(err_code);

}

/**@brief Function for handling an event from the Connection Parameters Module. *

• @details This function will be called for all events in the Connection Parameters Module

•      which are passed to the application.
  

• @note All this function does is to disconnect. This could have been done by simply setting

•   the disconnect_on_fail config parameter, but instead we use the event handler
  

•   mechanism to demonstrate its use.
  

• @param[in] p_evt Event received from the Connection Parameters Module. */ static void on_conn_params_evt(ble_conn_params_evt_t * p_evt) { uint32_t err_code;

  if(p_evt->evt_type == BLE_CONN_PARAMS_EVT_FAILED) { err_code = sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_CONN_INTERVAL_UNACCEPTABLE); APP_ERROR_CHECK(err_code); } }

/**@brief Function for handling errors from the Connection Parameters module. *

• @param[in] nrf_error Error code containing information about what went wrong. */ static void conn_params_error_handler(uint32_t nrf_error) { APP_ERROR_HANDLER(nrf_error); }

/**@brief Function for initializing the Connection Parameters module. */ static void conn_params_init(void) { uint32_t err_code; ble_conn_params_init_t cp_init;

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

cp_init.p_conn_params                  = NULL;
cp_init.first_conn_params_update_delay = FIRST_CONN_PARAMS_UPDATE_DELAY;
cp_init.next_conn_params_update_delay  = NEXT_CONN_PARAMS_UPDATE_DELAY;
cp_init.max_conn_params_update_count   = MAX_CONN_PARAMS_UPDATE_COUNT;
cp_init.start_on_notify_cccd_handle    = BLE_GATT_HANDLE_INVALID;
cp_init.disconnect_on_fail             = false;
cp_init.evt_handler                    = on_conn_params_evt;
cp_init.error_handler                  = conn_params_error_handler;

err_code = ble_conn_params_init(&cp_init);
APP_ERROR_CHECK(err_code);

}

/**@brief Function for putting the chip into sleep mode. *

• @note This function will not return. */ static void sleep_mode_enter(void) { uint32_t err_code = bsp_indication_set(BSP_INDICATE_IDLE); APP_ERROR_CHECK(err_code);

  // Prepare wakeup buttons. err_code = bsp_btn_ble_sleep_mode_prepare(); APP_ERROR_CHECK(err_code);

  // Go to system-off mode (this function will not return; wakeup will cause a reset). err_code = sd_power_system_off(); APP_ERROR_CHECK(err_code); }

/**@brief Function for handling advertising events. *

• @details This function will be called for advertising events which are passed to the application.

• @param[in] ble_adv_evt Advertising event. */ static void on_adv_evt(ble_adv_evt_t ble_adv_evt) { uint32_t err_code;

  switch (ble_adv_evt) { case BLE_ADV_EVT_FAST: err_code = bsp_indication_set(BSP_INDICATE_ADVERTISING); APP_ERROR_CHECK(err_code); break; case BLE_ADV_EVT_IDLE: sleep_mode_enter(); break; default: break; } }

/**@brief Function for the application's SoftDevice event handler. *

• @param[in] p_ble_evt SoftDevice event. */ static void on_ble_evt(ble_evt_t * p_ble_evt) { uint32_t err_code;

  switch (p_ble_evt->header.evt_id) { case BLE_GAP_EVT_CONNECTED: err_code = bsp_indication_set(BSP_INDICATE_CONNECTED); APP_ERROR_CHECK(err_code); m_conn_handle = p_ble_evt->evt.gap_evt.conn_handle; break;

   case BLE_GAP_EVT_DISCONNECTED:
       err_code = bsp_indication_set(BSP_INDICATE_IDLE);
       APP_ERROR_CHECK(err_code);
       m_conn_handle = BLE_CONN_HANDLE_INVALID;
       break;
  
   case BLE_GAP_EVT_SEC_PARAMS_REQUEST:
       // Pairing not supported
       err_code = sd_ble_gap_sec_params_reply(m_conn_handle, BLE_GAP_SEC_STATUS_PAIRING_NOT_SUPP, NULL, NULL);
       APP_ERROR_CHECK(err_code);
       break;
  
   case BLE_GATTS_EVT_SYS_ATTR_MISSING:
       // No system attributes have been stored.
       err_code = sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0, 0);
       APP_ERROR_CHECK(err_code);
       break;
  
   default:
       // No implementation needed.
       break;
  

  } }

/**@brief Function for dispatching a SoftDevice event to all modules with a SoftDevice

•    event handler.
  

• @details This function is called from the SoftDevice event interrupt handler after a

•      SoftDevice event has been received.
  

• @param[in] p_ble_evt SoftDevice event. */ static void ble_evt_dispatch(ble_evt_t * p_ble_evt) { ble_conn_params_on_ble_evt(p_ble_evt); ble_nus_on_ble_evt(&m_nus, p_ble_evt); on_ble_evt(p_ble_evt); ble_advertising_on_ble_evt(p_ble_evt); bsp_btn_ble_on_ble_evt(p_ble_evt);

}

/**@brief Function for the SoftDevice initialization. *

• @details This function initializes the SoftDevice and the BLE event interrupt. */ static void ble_stack_init(void) { uint32_t err_code;

  nrf_clock_lf_cfg_t clock_lf_cfg = NRF_CLOCK_LFCLKSRC;

  // Initialize SoftDevice. SOFTDEVICE_HANDLER_INIT(&clock_lf_cfg, NULL);

  ble_enable_params_t ble_enable_params; err_code = softdevice_enable_get_default_config(CENTRAL_LINK_COUNT, PERIPHERAL_LINK_COUNT, &ble_enable_params); APP_ERROR_CHECK(err_code);

  //Check the ram settings against the used number of links CHECK_RAM_START_ADDR(CENTRAL_LINK_COUNT,PERIPHERAL_LINK_COUNT); // Enable BLE stack. err_code = softdevice_enable(&ble_enable_params); APP_ERROR_CHECK(err_code);

  // Subscribe for BLE events. err_code = softdevice_ble_evt_handler_set(ble_evt_dispatch); APP_ERROR_CHECK(err_code); }

/**@brief Function for handling events from the BSP module. *

• @param[in] event Event generated by button press. */ void bsp_event_handler(bsp_event_t event) { uint32_t err_code; switch (event) { case BSP_EVENT_SLEEP: sleep_mode_enter(); break;

   case BSP_EVENT_DISCONNECT:
       err_code = sd_ble_gap_disconnect(m_conn_handle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);
       if (err_code != NRF_ERROR_INVALID_STATE)
       {
           APP_ERROR_CHECK(err_code);
       }
       break;
  
   case BSP_EVENT_WHITELIST_OFF:
       err_code = ble_advertising_restart_without_whitelist();
       if (err_code != NRF_ERROR_INVALID_STATE)
       {
           APP_ERROR_CHECK(err_code);
       }
       break;
   				
   case BSP_EVENT_KEY_0:
   				LEDS_ON(BSP_LED_1_MASK);
       break;
  
   case BSP_EVENT_KEY_1:
   				LEDS_OFF(BSP_LED_1_MASK);
       break;						
  
   default:
       break;
  

  } }

/**@brief Function for handling app_uart events. *

• @details This function will receive a single character from the app_uart module and append it to

•      a string. The string will be be sent over BLE when the last character received was a 
  

•      'new line' i.e '\n' (hex 0x0D) or if the string has reached a length of 
  

•      @ref NUS_MAX_DATA_LENGTH.
  

*/ /**@snippet [Handling the data received over UART] */ void uart_event_handle(app_uart_evt_t * p_event) { static uint8_t data_array[BLE_NUS_MAX_DATA_LEN]; static uint8_t index = 0; uint32_t err_code;

switch (p_event->evt_type)
{
    case APP_UART_DATA_READY:
        UNUSED_VARIABLE(app_uart_get(&data_array[index]));
        index++;

        if ((data_array[index - 1] == '\n') || (index >= (BLE_NUS_MAX_DATA_LEN)))
        {
            err_code = ble_nus_string_send(&m_nus, data_array, index);
            if (err_code != NRF_ERROR_INVALID_STATE)
            {
                APP_ERROR_CHECK(err_code);
            }
            
            index = 0;
        }
        break;

    case APP_UART_COMMUNICATION_ERROR:
        APP_ERROR_HANDLER(p_event->data.error_communication);
        break;

    case APP_UART_FIFO_ERROR:
        APP_ERROR_HANDLER(p_event->data.error_code);
        break;

    default:
        break;
}

} /**@snippet [Handling the data received over UART] */

/@brief Function for initializing the UART module. */ /@snippet [UART Initialization] */ static void uart_init(void) { uint32_t err_code; const app_uart_comm_params_t comm_params = { RX_PIN_NUMBER, TX_PIN_NUMBER, RTS_PIN_NUMBER, CTS_PIN_NUMBER, APP_UART_FLOW_CONTROL_ENABLED, false, UART_BAUDRATE_BAUDRATE_Baud115200 };

APP_UART_FIFO_INIT( &comm_params,
                   UART_RX_BUF_SIZE,
                   UART_TX_BUF_SIZE,
                   uart_event_handle,
                   APP_IRQ_PRIORITY_LOW,
                   err_code);
APP_ERROR_CHECK(err_code);

} /**@snippet [UART Initialization] */

/**@brief Function for initializing the Advertising functionality. */ static void advertising_init(void) { uint32_t err_code; ble_advdata_t advdata; ble_advdata_t scanrsp;

// Build advertising data struct to pass into @ref ble_advertising_init.
memset(&advdata, 0, sizeof(advdata));
advdata.name_type          = BLE_ADVDATA_FULL_NAME;
advdata.include_appearance = false;
advdata.flags              = BLE_GAP_ADV_FLAGS_LE_ONLY_LIMITED_DISC_MODE;

memset(&scanrsp, 0, sizeof(scanrsp));
scanrsp.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
scanrsp.uuids_complete.p_uuids  = m_adv_uuids;

ble_adv_modes_config_t options = {0};
options.ble_adv_fast_enabled  = BLE_ADV_FAST_ENABLED;
options.ble_adv_fast_interval = APP_ADV_INTERVAL;
options.ble_adv_fast_timeout  = APP_ADV_TIMEOUT_IN_SECONDS;

err_code = ble_advertising_init(&advdata, &scanrsp, &options, on_adv_evt, NULL);
APP_ERROR_CHECK(err_code);

}

/**@brief Function for initializing buttons and leds. *

• @param[out] p_erase_bonds Will be true if the clear bonding button was pressed to wake the application up. */ static void buttons_leds_init(bool * p_erase_bonds) { bsp_event_t startup_event;

  uint32_t err_code = bsp_init(BSP_INIT_LED | BSP_INIT_BUTTONS, APP_TIMER_TICKS(100, APP_TIMER_PRESCALER), bsp_event_handler); APP_ERROR_CHECK(err_code);

  err_code = bsp_btn_ble_init(NULL, &startup_event); APP_ERROR_CHECK(err_code);

  *p_erase_bonds = (startup_event == BSP_EVENT_CLEAR_BONDING_DATA); }

/**@brief Function for placing the application in low power state while waiting for events. */ static void power_manage(void) { uint32_t err_code = sd_app_evt_wait(); APP_ERROR_CHECK(err_code); }

/**

• @brief ADC interrupt handler.

• Prints ADC results on hardware UART and over BLE via the NUS service. / static void adc_event_handler(nrf_drv_adc_evt_t const * p_event) { uint8_t adc_result[ADC_BUFFER_SIZE2];

  if (p_event->type == NRF_DRV_ADC_EVT_DONE) { adc_event_counter++; printf(" ADC event counter: %d\r\n", adc_event_counter); uint32_t i; for (i = 0; i < p_event->data.done.size; i++) { printf("Sample value %d: %d\r\n", i+1, p_event->data.done.p_buffer[i]); //Print ADC result on hardware UART adc_result[(i2)] = p_event->data.done.p_buffer[i] >> 8; adc_result[(i2)+1] = p_event->data.done.p_buffer[i]; } if(ADC_BUFFER_SIZE <= 10) { ble_nus_string_send(&m_nus, &adc_result[0], ADC_BUFFER_SIZE*2); //Send ADC result over BLE via NUS service } LEDS_INVERT(BSP_LED_3_MASK); //Indicate sampling complete on LED 4 } }

/**

• @brief ADC initialization. */ static void adc_config(void) { ret_code_t ret_code; nrf_drv_adc_config_t config = NRF_DRV_ADC_DEFAULT_CONFIG;

  ret_code = nrf_drv_adc_init(&config, adc_event_handler); APP_ERROR_CHECK(ret_code);

  nrf_drv_adc_channel_enable(&m_channel_config); }

/**@brief Application main function. */ int main(void) { uint32_t err_code; bool erase_bonds;

// Initialize.
APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
uart_init();

buttons_leds_init(&erase_bonds);
ble_stack_init();
gap_params_init();
services_init();
advertising_init();
conn_params_init();

printf("\r\nUART Start!\r\n");
err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
APP_ERROR_CHECK(err_code);

  adc_config();

// Enter main loop.
for (;;)
{
    APP_ERROR_CHECK(nrf_drv_adc_buffer_convert(adc_buffer,ADC_BUFFER_SIZE));   //Allocate buffer for ADC
    for (uint32_t i = 0; i < ADC_BUFFER_SIZE; i++)
    {
        nrf_drv_adc_sample();           // manually trigger ADC conversion
        power_manage();                 // CPU enter sleep mode during sampling. CPU will be enabled again when ADC interrupt occurs and adc_event_handler is called
        LEDS_INVERT(BSP_LED_1_MASK);    // Indicate sampling complete
        nrf_delay_ms(250);              // Slow down sampling frequency with 250ms blocking delay
    }
}

}

/**

• @} */

[Hung Bui]

@Mostafa: You need to get your hands dirty and come back if you got some issues.