是的，为了读取BLE的值，需要先发送写请求。以下是使用Nordic nRF52 SDK中的代码示例：

首先，必须在特征值上启用通知。以下代码演示如何启用通知：

uint32_t err_code; ble_gatts_value_t gatts_value; ble_gatts_char_md_t char_md; ble_gatts_attr_md_t attr_md; ble_gatts_attr_t attr_char_value; ble_uuid_t char_uuid;

// 初始化UUID char_uuid.type = p_custom_service->uuid_type; char_uuid.uuid = SOME_UUID;

// 初始化属性元数据的值 memset(&char_md, 0, sizeof(char_md)); char_md.char_props.notify = 1; char_md.p_char_user_desc = NULL; char_md.p_char_pf = NULL; char_md.p_user_desc_md = NULL; char_md.p_cccd_md = NULL; char_md.p_sccd_md = NULL;

// 初始化属性管理数据的值 memset(&attr_md, 0, sizeof(attr_md)); attr_md.read_perm = p_custom_service->custom_value_char_attr_md.read_perm; attr_md.write_perm = p_custom_service->custom_value_char_attr_md.write_perm; attr_md.vloc = BLE_GATTS_VLOC_STACK; attr_md.rd_auth = 0; attr_md.wr_auth = 0; attr_md.vlen = 0;

// 初始化GATT属性值的值 memset(&gatts_value, 0, sizeof(ble_gatts_value_t)); gatts_value.len = sizeof(uint32_t); gatts_value.offset = 0; gatts_value.p_value = (uint8_t *) initial_custom_value;

// 初始化GATT属性的值 memset(&attr_char_value, 0, sizeof(attr_char_value)); attr_char_value.p_uuid = &char_uuid; attr_char_value.p_attr_md = &attr_md; attr_char_value.init_len = sizeof(uint32_t); attr_char_value.init_offs = 0; attr_char_value.max_len = MAX_CUSTOM_VALUE_CHAR_LEN; attr_char_value.p_value = (uint8_t *) initial_custom_value;

// 添加要添加到属性列表中的属性 err_code = sd_ble_gatts_characteristic_add(p_custom_service->service_handle, &char_md, &attr_char_value, &p_custom_service->custom_value_handles); if (err_code != NRF_SUCCESS) { return err_code; }

然后，可以使用以下代码发送写请求：

uint32_t err_code; ble_gatts_value_t gatts_value;

// 初始化写请求 memset(&gatts_value, 0, sizeof(gatts_value));