How to correctly set channel map of next connection?

[Gregor Bader]

I'm using s130_nrf51_2.0.0-4.alpha as central and do some testing with channel map. I set the channel map before I'm trying to connect to a peripheral with:

  ble_opt_t opt;
  memset(&opt, 0, sizeof(opt));
  opt.gap_opt.ch_map.ch_map[0] = 0xFF;
  opt.gap_opt.ch_map.ch_map[1] = 0x0F;
  err_code = sd_ble_opt_set(BLE_GAP_OPT_CH_MAP, &opt);
  APP_ERROR_CHECK(err_code);

  // Initiate connection.
  err_code = sd_ble_gap_connect(peer_addr,
                                &m_scan_param,
                                &conn_params);

But when I check the current active channel map during the connection, I get the default channel map!

  ble_opt_t opt;
  memset(&opt, 0, sizeof(opt));
  opt.gap_opt.ch_map.conn_handle = m_conn_handle_central;
  sd_ble_opt_get(BLE_GAP_OPT_CH_MAP, &opt);
  APP_LOG("ChMap %02X %02X %02X %02X %02X\r\n",
    opt.gap_opt.ch_map.ch_map[0], opt.gap_opt.ch_map.ch_map[1], opt.gap_opt.ch_map.ch_map[2],
    opt.gap_opt.ch_map.ch_map[3], opt.gap_opt.ch_map.ch_map[4]);

Output:

ChMap FF FF FF FF 1F

[Ole Bauck]

Setting the channel map may take some time, see here. Try to call sd_ble_opt_get(...) at a later point in time.

[Gregor Bader]

Your reference seems to only apply when changing the channel map during an active connection. But I want to change it before a connection.

And what is "some time" ? 1s or 1 minute?

[Ole Bauck]

I tested it before calling sd_ble_gap_connect(...) as in your question and it worked. I checked in the connection parameter update request event (5 seconds after connection) . For the time it takes to change the map, this is from the bluetooth spec: "If this command is used, updates should be sent within 10 seconds, of the Host knowing that the channel classification has changed. The interval between two successive commands sent shall be at least 1 second."

[Gregor Bader]

Regarding your test, is the channel map only updated with "connection parameter update request"???

[Ole Bauck]

I was just using the connection parameter update request event to read the channel map since I knew this happened 5 seconds after the connection. The channel map have been updated some time in between. Feel free to start a timer (e.g. app_timer) on connection and read the channel map sooner to see when it changes.