https://devzone.nordicsemi.com/f/nordic-q-a/74512/regarding-the-one-unit-with-advertisement-only-on-channel-37-and-the-other-unit-scan-on-only-channel-37I am using the SDK 17.0.2 to make the advertisement and scanning for the two nrf52840 boards. One unit with extended advertisement only on channel 37 and the other unit scan on only channel 37. I am not sure whether that is correct or not, could you pleaseen-USTelligent Community 13Wed, 28 Apr 2021 07:33:27 GMThttps://devzone.nordicsemi.com/thread/307153?ContentTypeID=1Wed, 28 Apr 2021 07:33:27 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4adc3c74-f70d-49ff-82d0-48e2a40630a1Amanda Hsieh<p>Hi Luan,&nbsp;</p> <p><span>When&nbsp;starting scanning or advertisement you have the possibility to control a parameter called:&nbsp;<a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s140.api.v7.2.0/group___b_l_e___g_a_p___s_t_r_u_c_t_u_r_e_s.html#gac2e09c679d84d885adbb28d0ab51a7ad">ble_gap_ch_mask_t</a>&nbsp;ble_gap_scan_params_t::<a href="https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.s140.api.v7.2.0/structble__gap__scan__params__t.html#a530709ea04787c9b8be6611d43416354">channel_mask</a>&nbsp;</span></p> <p><span>Take note of what the documentation says about the ble_gap_ch_mask_t structure:</span></p> <blockquote> <ul> <li><span>Channel mask (40 bits).</span></li> <li><span>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. </span></li> <li><span>The LSB contained in array element 0 represents channel index 0, and bit 39 represents&nbsp;channel index 39. If a bit is set to 1, the channel is not used.</span></li> </ul> </blockquote> <p><span>Also, see my colleague Jared&#39;s explanation in this <a href="https://devzone.nordicsemi.com/f/nordic-q-a/66359/configure-the-advertising-channel/271664#271664">post</a>.&nbsp;</span></p> <p><span>-Amanda H.</span></p> <p><span></span></p><div style="clear:both;"></div>