Disabling AFH (Adaptive Frequency Hopping)

Question

Please tell me about AFH (Adaptive Frequency Hopping). 
 SDK：15.3.0 例：ble_app_multirole_lesc DeviceA：EYSHJNZWZ（nRF52832） 
 In AFH (Adaptive Frequency Hopping), the frequency is switched between 0 to 36 CH when connected and 37 to 39 CH when advertised. Is it possible to disable AFH? In other words, is it possible to fix to any channel? Please tell me if there is a way.

bjorn-spockeli · Accepted Answer

Hi Hiroki-san, 
 it is the Central device that dictates the channel map used in a connection and it can be modified through the sd_ble_opt_set API, see S132 SoftDevice v7.0.1: ble_gap_opt_ch_map_t Struct Reference . So by removing all but one channel from the channel map, you should be able to restrict communication to a single channel. 
 Best regards 
 Bjørn

Dmitry · Answer

Just to note that such configuration will not match Bluetooth specification that says: The minimum number of used channels shall be 2.

Dmitry · Answer

I believe it's possible, I can't say for sure. Try to mask all but one channel: 
 ble_opt_t opt;
 memset(&opt, 0, sizeof(opt));
 opt.gap_opt.ch_map.ch_map[0] = 0xFE; // ch.1
 opt.gap_opt.ch_map.ch_map[1] = 0xFF;
 opt.gap_opt.ch_map.ch_map[2] = 0xFF;
 opt.gap_opt.ch_map.ch_map[3] = 0xFF;
 opt.gap_opt.ch_map.ch_map[4] = 0x1F; sd_ble_opt_set(BLE_GAP_OPT_CH_MAP, &opt); 
 
 takashina hiroki said: Can I disable AFH in the same way when advertising as a peripheral device? 
 There is no AFH when advertising, instead, device is advertising sequentially on all 3 channels. Yes, you can change advertising channel mask in ble_gap_adv_params_t.

Jimmy Wong · Answer

You can use the channel survey and do the channel map update from central. The example code is here. https://github.com/jimmywong2003/nrf52-central-channel-map-update-with-survey

Disabling AFH (Adaptive Frequency Hopping)

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