Update BLE Characteristic from ENUM

[aplatts]

Hi

I would like to use an ENUM and STUCT within my application to maintain device state (IDLE, RUNNING etc). This state needs to update a BLE Characteristic. I have the BLE Service and Characteristic running but am struggling to send the ENUM as a single byte (uint8_t).

The ENUM & STRUCT is as follows:

typedef enum
{
    IDLE    = 0x00,    //0
    RUNNING = 0x01,    //1
    FAULT   = 0x09     //9
} m_srm_state_evt_type_t;

typedef struct
{
    m_srm_state_evt_type_t evt_type;
} m_srm_state_type_t;
static m_srm_state_type_t m_srm_state;

And the BLE update char is as follows:

case BLE_SRVC_OPT_EVT_CONNECTED:
            uint8_t value[1]            = {m_srm_state.value};
            err_code = ble_srvc_opt_custom_value_update(&m_cus, value);
            APP_ERROR_CHECK(err_code);
            break;

I know it's my lack of programming skills, but really stuck on this one. Thanks in advance.

[Jared]

Hi,

I'm interested in seeing more of your code, specifically the initialization of the service and the ble_srvc_opt_custom_value_update(). Also

I have the BLE Service and Characteristic running but am struggling to send the ENUM as a single byte (uint8_t).

 What exactly happens when you run the application? Are you getting any errors? Have you tried debugging your application?

regards

Jared

[aplatts]

Hi,

The code won't compile as is, but if I replace the ENUM var with a simple byte of 01 -

ret_code_t err_code;
uint8_t value            = 0;
err_code = ble_srvc_opt_custom_value_update(&m_cus, value);
APP_ERROR_CHECK(err_code);

This code is initiated as soon as the following criteria is met within  this static void -

static void on_srvc_opt_evt(ble_srvc_opt_t     * p_cus_service,
                       ble_srvc_opt_evt_t * p_evt)
{

    ret_code_t err_code;
    uint8_t value            = 0;
    
    switch(p_evt->evt_type)
    {

        case BLE_SRVC_OPT_EVT_NOTIFICATION_ENABLED:
            break;

        case BLE_SRVC_OPT_EVT_NOTIFICATION_DISABLED:
            break;

        case BLE_SRVC_OPT_EVT_CONNECTED:
            //Set BLE Characteristics on connection
            err_code = ble_srvc_opt_custom_value_update(&m_cus, value);
            APP_ERROR_CHECK(err_code);
            break;

        case BLE_SRVC_OPT_EVT_DISCONNECTED:
            break;

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

I get the following crash:

<info> app: Fast advertising.

<info> app: ble_srvc_data Custom Characteristic - BLE_GAP_EVT_CONNECTED

<info> app: ble_srvc_opt Custom Characteristic - BLE_GAP_EVT_CONNECTED

<info> app: In ble_srvc_opt_custom_value_update. 

<error> app: ERROR 13313 [Unknown error code] at ../../../main.c:206

PC at: 0x0002D141

<error> app: End of error report

Lines 205 and 206 in main.c are:

err_code = ble_srvc_opt_custom_value_update(&m_cus, value);
APP_ERROR_CHECK(err_code);

Value Update Code:-

uint32_t ble_srvc_opt_custom_value_update(ble_srvc_opt_t * p_cus, uint8_t custom_value)
{
    NRF_LOG_INFO("In ble_srvc_opt_custom_value_update. \r\n"); 
    if (p_cus == NULL)
    {
        return NRF_ERROR_NULL;
    }

    uint32_t err_code = NRF_SUCCESS;
    ble_gatts_value_t gatts_value;

    // Initialize value struct.
    memset(&gatts_value, 0, sizeof(gatts_value));

    gatts_value.len     = sizeof(uint8_t);
    gatts_value.offset  = 0;
    gatts_value.p_value = &custom_value;

    // Update database.
    err_code = sd_ble_gatts_value_set(p_cus->conn_handle,
                                      p_cus->custom_value_handles.value_handle,
                                      &gatts_value);
    if (err_code != NRF_SUCCESS)
    {
        return err_code;
    }

    // Send value if connected and notifying.
    if ((p_cus->conn_handle != BLE_CONN_HANDLE_INVALID)) 
    {
        ble_gatts_hvx_params_t hvx_params;

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

        hvx_params.handle = p_cus->custom_value_handles.value_handle;
        hvx_params.type   = BLE_GATT_HVX_NOTIFICATION;
        hvx_params.offset = gatts_value.offset;
        hvx_params.p_len  = &gatts_value.len;
        hvx_params.p_data = gatts_value.p_value;

        err_code = sd_ble_gatts_hvx(p_cus->conn_handle, &hvx_params);
    }
    else
    {
        err_code = NRF_ERROR_INVALID_STATE;
    }


    return err_code;
}

Thanks

[Jared]

Hi.

ERROR 13313 is a BLE_ERROR_GATTS_SYS_ATTR_MISSING which is returned by sd_ble_gatts_hvx(). Could you try the solution proposed in this case.  Also I can't see that value is a struct member from your definition of the struct m_srm_state. It seems that the struct member is called evt_type. 

[aplatts]

Hi

I think the issue is that I am attempting to send a Characteristic Value before it being ready (i.e. I'm sending as soon as BLE_SRVC_OPT_EVT_CONNECTED). As this is at the Service level, I assume that the Characteristic could still be being negotiated.

Would this make sense?

[Jared]

Hi,

Did you try the workaround suggest in the linked case in the previous reply? 

You could try setting err_code =sd_ble_gatts_sys_attr_set(m_conn_handle, NULL, 0)  before you call  ble_srvc_opt_custom_value_update(). And you should make sure that notifications is enabled.

regards

Jared

[aplatts]

Hi

I have looked at my code and carried out a few modifications and have a better understand how the SoftDevice works.

The following is working, on the following event, it calls handle_ble_char:

case BLE_SRVC_OPT_EVT_CONNECTED:
        t_value = SET;
        handle_ble_char(p_cus_service, &p_cus_service->status_char_handles , &t_value);
        break;

The structure of handle_ble_char is as follows:

static void handle_ble_char (ble_srvc_opt_t *p_service, ble_gatts_char_handles_t *p_char_handle, m_setget *p_type) {

    uint32_t err_code;
    ble_gatts_value_t	t_value;

    //Get & Set for ble_src_opt - Char - Status
    if (p_char_handle->value_handle == m_cus.status_char_handles.value_handle) {
        
        t_value.p_value = &m_srm_state.evt_type;
	    t_value.len      = 1;
	    t_value.offset   = 0;

        switch (*p_type)
        {
        case SET:
            err_code = sd_ble_gatts_value_set(p_service->conn_handle, p_char_handle->value_handle, &t_value);
    	    APP_ERROR_CHECK(err_code);
            break;
        case GET:
            err_code = sd_ble_gatts_value_get(p_service->conn_handle, p_char_handle->value_handle, &t_value);
    	    APP_ERROR_CHECK(err_code);
            break;
        default:
            break;
        }
    }

}

This is a universal bit of code which allows me to tell it which service and characteristic to set or get.

It is working as planned now...thanks for the help on this one.