Hello,
My project requires me to send acceleration data to phone. So, i have started with Custom BLE app.
Since i need to send 3 values, of x, y and z-axis. So i need to send multiple values to same characteristic. Can you guide me regarding this?
If any other approach serves me better, kindly do suggest me.
Thank you so much, awneil and Karl Ylvisaker for your suggestions.
So,
Question 1
a. Sending 3 values, one after the other , through the same value and characteristics (This would consume power for all 3 transmissions)
b. Sending 3 values to 3 different characteristics (Would this also means im trying to send the data in 3 transmissions?)
c. Sending all 3 values packed would save power and could send all data in one transmission.
Kindly correct me, if I'm wrong.
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Question 2
So, currently my code is pushing 8 bits of data . To change this to 64bits, i tried following corrections, Kindly let me know, if this is okay and if anything else has to be changed
a. change the size of custom value (main.c)
b. change the argument size and gatts_value.len (ble_cus.c)
uint32_t ble_cus_custom_value_update(ble_cus_t * p_cus, uint64_t custom_value){
NRF_LOG_INFO("In ble_cus_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(uint64_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);
NRF_LOG_INFO("sd_ble_gatts_hvx result: %x. \r\n", err_code);
}
else
{
err_code = NRF_ERROR_INVALID_STATE;
NRF_LOG_INFO("sd_ble_gatts_hvx result: NRF_ERROR_INVALID_STATE. \r\n");
}
return err_code;
}
c. Change the size of custom value in prototype declaration. (ble_cus.h)
d. Change the value of structure of GATT attribute value and HVx value as below (ble_gatts.h)
/**@brief GATT Attribute Value. */
typedef struct
{
uint64_t len; /**< Length in bytes to be written or read. Length in bytes written or read after successful return.*/
uint64_t offset; /**< Attribute value offset. */
uint64_t *p_value; /**< Pointer to where value is stored or will be stored.
If value is stored in user memory, only the attribute length is updated when p_value == NULL.
Set to NULL when reading to obtain the complete length of the attribute value */
} ble_gatts_value_t;
/**@brief GATT HVx parameters. */
typedef struct
{
uint64_t handle; /**< Characteristic Value Handle. */
uint64_t type; /**< Indication or Notification, see @ref BLE_GATT_HVX_TYPES. */
uint64_t offset; /**< Offset within the attribute value. */
uint64_t *p_len; /**< Length in bytes to be written, length in bytes written after return. */
uint64_t const *p_data; /**< Actual data content, use NULL to use the current attribute value. */
} ble_gatts_hvx_params_t;