Each sub-carrier index of CSI using the [get-started]

[zhy102]

Thanks for your opening source! I have a question about the received data by using the get-started. In this way, i can collect CSI with 256 total bytes and i want to konw each sub-carrier index of CSI from esp32 devices. Although the link "https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-guides/wifi.html#wi-fi-channel-state-information" was offered, there are three confounding terms with 256 total bytes, which one is correct？

[MacChu0315-Espressif]

If the three confounding terms you mentioned means 'none / below / above in secondary channel + HT + 20MHz + non STBC', they means the same thing actually. For if you make the bandwidth to be 20MHz, all the subcarriers will strickly distribute in the channel that you choosed.

And comment for esp_wifi_set_channel function is attached down here:
// @param primary for HT20, primary is the channel number, for HT40, primary is the primary channel
// @param second for HT20, second is ignored, for HT40, second is the second channel
esp_err_t esp_wifi_set_channel(uint8_t primary, wifi_second_chan_t second);