import uos
import network
from flashbdev import bdev

def wifi():
    import ubinascii
    ap_if = network.WLAN(network.AP_IF)
    essid = b"MicroPython-%s" % ubinascii.hexlify(ap_if.mac()[-3:])
    ap_if.config(essid=essid, authmode=network.AUTH_WPA_WPA2_PSK, password=b"micropythoN")

def check_bootsec():
    buf = bytearray(bdev.SEC_SIZE)
    bdev.readblocks(0, buf)
    empty = True
    for b in buf:
        if b != 0xff:
            empty = False
            break
    if empty:
        return True
    fs_corrupted()

def fs_corrupted():
    import time
    while 1:
        print("""\
FAT filesystem appears to be corrupted. If you had important data there, you
may want to make a flash snapshot to try to recover it. Otherwise, perform
factory reprogramming of MicroPython firmware (completely erase flash, followed
by firmware programming).
""")
        time.sleep(3)

def setup():
    check_bootsec()
    print("Performing initial setup")
    wifi()
    uos.VfsFat.mkfs(bdev)
    vfs = uos.VfsFat(bdev, "")
    with open("/boot.py", "w") as f:
        f.write("""\
# This file is executed on every boot (including wake-boot from deepsleep)
import webrepl
webrepl.start()
""")
    return vfs

import uos
import network
from flashbdev import bdev

def wifi():
    import ubinascii
    ap_if = network.WLAN(network.AP_IF)
    essid = b"MicroPython-%s" % ubinascii.hexlify(ap_if.config("mac")[-3:])
    ap_if.config(essid=essid, authmode=network.AUTH_WPA_WPA2_PSK, password=b"micropythoN")

def check_bootsec():
    buf = bytearray(bdev.SEC_SIZE)
    bdev.readblocks(0, buf)
    empty = True
    for b in buf:
        if b != 0xff:
            empty = False
            break
    if empty:
        return True
    fs_corrupted()

def fs_corrupted():
    import time
    while 1:
        print("""\
FAT filesystem appears to be corrupted. If you had important data there, you
may want to make a flash snapshot to try to recover it. Otherwise, perform
factory reprogramming of MicroPython firmware (completely erase flash, followed
by firmware programming).
""")
        time.sleep(3)

def setup():
    check_bootsec()
    print("Performing initial setup")
    wifi()
    uos.VfsFat.mkfs(bdev)
    vfs = uos.VfsFat(bdev, "")
    with open("/boot.py", "w") as f:
        f.write("""\
# This file is executed on every boot (including wake-boot from deepsleep)
import webrepl
webrepl.start()
""")
    return vfs

Update for nic.mac() method being gone.