How can set listening single channel on scanner?

Question

My Environment 
 
 Nrf52840 
 SDK : nrf51_15.0.0 
 soft device : s140 
 Target : Scanner (central) 
 
 I am trying to set GAP parameter for listening single channel that is from beacon to use single channel. 
 
 so. i have had to set GAP Parameter for scanning but it is not work. 
 how can i right approach ? Please let me know 
 
 Question 
 1. How can i set GAP parameter for listening single channel on central(scanner) 
 * Please let me example code or sample link , if you can

MartinBL · Accepted Answer

Hi, 
 Use the ble_gap_ch_mask_t structure in included in the ble_gap_scan_params_t structure and pass that to sd_ble_gap_scan_start () . Take note of what the documentation says about the ble_gap_ch_mask_t structure: 
 
 * Every channel is represented with a bit positioned as per channel index defined in Bluetooth Core Specification v5.0, * Vol 6, Part B, Section 1.4.1. The LSB contained in array element 0 represents channel index 0, and bit 39 represents * channel index 39. If a bit is set to 1, the channel is not used. 
 
 To avoid scanning on channel 39 for example, you can modify m_scan_params in the ble_app_uart_c example like this: 
 /** @brief Parameters used when scanning. */
static ble_gap_scan_params_t const m_scan_params =
{
 .active = 1,
 .interval = SCAN_INTERVAL,
 .window = SCAN_WINDOW,
 .timeout = SCAN_DURATION,
 .scan_phys = BLE_GAP_PHY_1MBPS,
 .filter_policy = BLE_GAP_SCAN_FP_ACCEPT_ALL,
 .channel_mask[4] = 0x80, // <- DON'T SCAN ON CHANNEL 39
};