Exploring Introduction to service structure

Question

I am new to BLE and I am exploring Introduction to service. However I am stuck with Step 1 and Step 2. Is Step 1: static ble_os_t m_our_service; (to declare a service) and step 2: our_service_init(ble_os_t*m_our_service); (the error says expected expression before ble_os_t). What is the way to define and initialise a service?

Karl Ylvisaker · Accepted Answer

Hello, 
 I am new to BLE and I am exploring Introduction to service. 
 Welcome! 
 However I am stuck with Step 1 and Step 2. Is Step 1: static ble_os_t m_our_service; (to declare a service) and step 2: our_service_init(ble_os_t*m_our_service); (the error says expected expression before ble_os_t). 
 How familiar are you with C and embedded programming? In short, we need to declare that a new service exists - and then we need to fill in the empty service with the contents and functionality it will provide, by initializing it. A more in-depth explanation of the concepts declaration, definition and initialization can be read here . 
 What is the way to define and initialise a service? 
 Have you retrieved the tutorials example code from the github ? Step 1 of the tutorial calls for declaration of a service structure. If you check out the our_service.h file, you will see the code exempt: /**
 * @brief This structure contains various status information for our service. 
 * It only holds one entry now, but will be populated with more items as we go.
 * The name is based on the naming convention used in Nordic's SDKs. 
 * 'ble’ indicates that it is a Bluetooth Low Energy relevant structure and 
 * ‘os’ is short for Our Service). 
 */
typedef struct
{
 uint16_t service_handle; /**< Handle of Our Service (as provided by the BLE stack). */
}ble_os_t; Relevant examples of other, similar, declarations can be seen in main.c, for example: static uint16_t m_conn_handle = BLE_CONN_HANDLE_INVALID; /**< Handle of the current connection. */ 
 2: our_service_init(ble_os_t*m_our_service); (the error says expected expression before ble_os_t). 
 Here, you are supposed to pass the function the service structure you declared earlier. Looking into the our_service.h file again, we see the following exempt: /**@brief Function for initializing our new service.
 *
 * @param[in] p_our_service Pointer to Our Service structure.
 */
void our_service_init(ble_os_t * p_our_service); Which means that the our_service_init function takes a pointer to a ble_os_t struct as its argument. You must therefore provide this when you call the function, and it is done by using the referencing operator &, i.e passing the argument &m_our_service. You should read more about referencing and pointers in this stackoverflow discussion , as it is crucial when working with C and embedded programming. Please let me know if anything should still be unclear! Best regards, Karl

Exploring Introduction to service structure

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