Add Pico W examples

pico_w/wifi_scan/CMakeLists.txt

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+add_executable(picow_wifi_scan_background
+        picow_wifi_scan.c
+        )
+target_include_directories(picow_wifi_scan_background PRIVATE
+        ${CMAKE_CURRENT_LIST_DIR}
+        ${CMAKE_CURRENT_LIST_DIR}/.. # for our common lwipopts
+        )
+target_link_libraries(picow_wifi_scan_background
+        pico_cyw43_arch_lwip_threadsafe_background
+        pico_stdlib
+        )
+
+pico_add_extra_outputs(picow_wifi_scan_background)
+
+add_executable(picow_wifi_scan_poll
+        picow_wifi_scan.c
+        )
+target_include_directories(picow_wifi_scan_poll PRIVATE
+        ${CMAKE_CURRENT_LIST_DIR}
+        ${CMAKE_CURRENT_LIST_DIR}/.. # for our common lwipopts
+        )
+target_link_libraries(picow_wifi_scan_poll
+        pico_cyw43_arch_lwip_poll
+        pico_stdlib
+        )
+pico_add_extra_outputs(picow_wifi_scan_poll)
+

pico_w/wifi_scan/lwipopts.h

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+#ifndef _LWIPOPTS_H
+#define _LWIPOPTS_H
+
+// Generally you would define your own explicit list of lwIP options
+// (see https://www.nongnu.org/lwip/2_1_x/group__lwip__opts.html)
+//
+// This example uses a common include to avoid repetition
+#include "lwipopts_examples_common.h"
+
+#endif

pico_w/wifi_scan/picow_wifi_scan.c

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+/**
+ * Copyright (c) 2022 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+
+#include "pico/stdlib.h"
+#include "pico/cyw43_arch.h"
+
+static int scan_result(void *env, const cyw43_ev_scan_result_t *result) {
+    if (result) {
+        printf("ssid: %-32s rssi: %4d chan: %3d mac: %02x:%02x:%02x:%02x:%02x:%02x sec: %u\n",
+            result->ssid, result->rssi, result->channel,
+            result->bssid[0], result->bssid[1], result->bssid[2], result->bssid[3], result->bssid[4], result->bssid[5],
+            result->auth_mode);
+    }
+    return 0;
+}
+
+#include "hardware/vreg.h"
+#include "hardware/clocks.h"
+
+int main() {
+    stdio_init_all();
+
+    if (cyw43_arch_init()) {
+        printf("failed to initialise\n");
+        return 1;
+    }
+
+    cyw43_arch_enable_sta_mode();
+
+    absolute_time_t scan_test = nil_time;
+    bool scan_in_progress = false;
+    while(true) {
+        if (absolute_time_diff_us(get_absolute_time(), scan_test) < 0) {
+            if (!scan_in_progress) {
+                cyw43_wifi_scan_options_t scan_options = {0};
+                int err = cyw43_wifi_scan(&cyw43_state, &scan_options, NULL, scan_result);
+                if (err == 0) {
+                    printf("\nPerforming wifi scan\n");
+                    scan_in_progress = true;
+                } else {
+                    printf("Failed to start scan: %d\n", err);
+                    scan_test = make_timeout_time_ms(10000); // wait 10s and scan again
+                }
+            } else if (!cyw43_wifi_scan_active(&cyw43_state)) {
+                scan_test = make_timeout_time_ms(10000); // wait 10s and scan again 
+                scan_in_progress = false; 
+            }
+        }
+        // the following #ifdef is only here so this same example can be used in multiple modes;
+        // you do not need it in your code
+#if PICO_CYW43_ARCH_POLL
+        // if you are using pico_cyw43_arch_poll, then you must poll periodically from your
+        // main loop (not from a timer) to check for WiFi driver or lwIP work that needs to be done.
+        cyw43_arch_poll();
+        sleep_ms(1);
+#else
+        // if you are not using pico_cyw43_arch_poll, then WiFI driver and lwIP work
+        // is done via interrupt in the background. This sleep is just an example of some (blocking)
+        // work you might be doing.
+        sleep_ms(1000);
+#endif
+    }
+
+    cyw43_arch_deinit();
+    return 0;
+}