Grep and parse the RSSI of received packets

ESP32_GetRSSI.c

/*  ESP32 Get RSSI of packets- Promiscuous Mode
    (C) 2017, Staubgeborener 
    https://github.com/Staubgeborener/ */

#include "esp_wifi.h"
#include "esp_wifi_internal.h"
#include "lwip/err.h"
#include "esp_system.h"
#include "esp_event.h"
#include "esp_event_loop.h"
#include "nvs_flash.h"

esp_err_t event_handler(void* ctx, system_event_t* event)
{
    return ESP_OK;
}

void wifi_promiscuous(void* buffer, wifi_promiscuous_pkt_type_t type)
{
    //parsing buffer data
    wifi_promiscuous_pkt_t* p = (wifi_promiscuous_pkt_t*)buffer;

    //see: https://github.com/espressif/esp-idf/blob/8e4a8e17037c51ce2452e55b5b75bbfaecb25838/components/esp32/include/esp_wifi_types.h#L192
    printf("%02d\n", p->rx_ctrl.rssi);
}

void app_main()
{
    nvs_flash_init();
    tcpip_adapter_init();
    ESP_ERROR_CHECK(esp_event_loop_init(event_handler, NULL));
    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));

    ESP_ERROR_CHECK(esp_wifi_set_storage(WIFI_STORAGE_RAM));
    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_NULL));
    ESP_ERROR_CHECK(esp_wifi_start());

    ESP_ERROR_CHECK(esp_wifi_set_country(WIFI_COUNTRY_EU)); //set country EU for channel range [1, 13]
    esp_wifi_set_channel(6, WIFI_SECOND_CHAN_NONE); //sniff only on channel 6. Increment this value in a loop for sniffing all channels

    esp_wifi_set_promiscuous_rx_cb(&wifi_promiscuous);
    esp_wifi_set_promiscuous(true); //as soon this flag is true, the callback will triggered for each packet
}

@prateekrajgautam Those libraries are parts of the official esp-idf.