WLAN connection of PicoW sometimes working, sometimes not

[jean-claudeF]

I am going mad with this connectivity problem. It is not reproducable.

My code is here:

import time, network, socket

ssid = "..." 
pwd = "..."

def start_wlan():
    # Disable AP!
    ap = network.WLAN(network.AP_IF)
    ap.active(False)    
    
    # Make wlan object
    wlan = network.WLAN(network.STA_IF)
    wlan.active(True)

    wlan_mac = wlan.config('mac')
    print("MAC Address:", wlan_mac)
    return wlan

def connect(wlan, ssid, pwd):
   # Connect wlan to existing WiFi 
   wlan.connect(ssid, pwd)
   cnt =0
   while cnt<10:
     if not wlan.isconnected():
        print("Connecting to ", ssid ,cnt)
        time.sleep(2)
        cnt+=1
     else:
        break
    
   if wlan.isconnected():
      print("Connected" )
      print("PicoW IP: ", wlan.ifconfig())
           
   else:
      print('No WiFi')
      
wlan = start_wlan()   
connect( wlan, ssid, pwd)

Most often it works and the output is like this:
MAC Address: b'(\xcd\xc1\x00\x08\x1f' Connected PicoW IP: ('192.168.0.114', '255.255.255.0', '192.168.0.100', '192.168.0.100')

But sometimes the program hangs in the while loop without connecting.

[mendenm]

Does this happen after you have left the WiFi idle for a very long (hours) time?

I had a random would-not-reconnect issue with my Pico-W, until I added a ping to it every so often (I'm using 5 seconds, probably could be once an hour and still be fine). Then the network worked forever (has been on for weeks). The symptom would be that it would permanently show ifconfig as all 0.0.0.0, but claim connectivity.

[jean-claudeF]

@mendenm:
This happens when I start my program in Thonny, just at the beginning.
It does not have anything to do with Thonny, I first noticed this behavior when I tried it in standalone mode, only connected to the power supply.
But the behavior is totally random, sometimes working, sometimes not.

[peterhinch]

Please explain the context in which this cod runs. Is it on power up, or is the code reconnecting? If reconnecting, how was the disconnect detected and what did the code do in response?

[mendenm]

Although you have already moved on, here is the code I use to maintain a network connection. I have never seen it fail (which is different than saying it won't fail for you!).

# a list  of networks to which I can connect.
netdict = {
    b"mynet1": "password1",
    b"mynet2": "password2"
}

async def keep_net_alive(verbose):
    global nic
    import network
    last_status = -1
    while nic != "STOP":
        stat = nic.status() if nic is not None else -4
        if stat < 0:
            if verbose and nic is not None: print("no net:", nic.status(), nic.ifconfig())
            if nic is not None: nic.active(False)
            last_status = stat
            #network hard crashed...
            network.hostname("powerline_pico")
            network.country('US')
            #ap = network.WLAN(network.AP_IF)
            #ap.active(False) #turn off any AP interface activity
            nic = network.WLAN(network.STA_IF)
            nic.active(True)
            await asyncio.sleep(1)
            if verbose: print("attempted activation:", nic.status())
        elif last_status < 0 or not nic.isconnected(): #alive, but not connected
            nets = nic.scan()
            if verbose: print("found", [str(x[0],'utf8') for x in nets])
            for net in nets:
                if net[0] in netdict:
                    nic.disconnect() #start  over here
                    nic.active(False)
                    await asyncio.sleep(1)
                    nic.active(True)
                    nic.connect(net[0], netdict[net[0]])
                    while nic.status() > network.STAT_IDLE and nic.status() != network.STAT_GOT_IP: 
                        await asyncio.sleep(1) #check again later
                    if verbose: print("connected to", str(net[0], 'utf8'), nic.ifconfig(), nic.config('hostname'))
                    break

            nic.config(hostname  = "powerline_pico")
            last_status = nic.status()
            await asyncio.sleep(1) #check again later
        else:
            config =  nic.ifconfig()
            uping.ping(config[-1], count = 1)
            if verbose: print("on net:", nic.status(), nic.ifconfig())
            await asyncio.sleep(5)            

[jean-claudeF]

Hey guys, it's really recomforting that you react so quickly to my question.
@mendenm: I'll have a look at your code soon.
Ooops, I see a lot of async statements that I have not used until now. But it is newer too late :-)

[mendenm]

you can easily do this without async. In fact, this was the first time I tried to do anything useful with async. This pico runs a microdot web server, exposing data it collects. asyncio was useful for that logic.

[jean-claudeF]

I tryed a simplified version now, without async.

netdict = {    b"...": "...",}

import time, network, socket, uping
verbose = True
nic = None

def keep_net_alive(verbose):
    
    global nic
    last_status = -1
    while nic != "STOP":
        stat = nic.status() if nic is not None else -4
        if stat < 0:
            if verbose and nic is not None: print("no net:", nic.status(), nic.ifconfig())
            if nic is not None: nic.active(False)
            last_status = stat
            #network hard crashed...
            ##network.hostname("powerline_pico")
            ##network.country('US')
            #ap = network.WLAN(network.AP_IF)
            #ap.active(False) #turn off any AP interface activity
            nic = network.WLAN(network.STA_IF)
            nic.active(True)
            time.sleep(1)
            if verbose: print("attempted activation:", nic.status())
        elif last_status < 0 or not nic.isconnected(): #alive, but not connected
            nets = nic.scan()
            if verbose: print("found", [str(x[0],'utf8') for x in nets])
            for net in nets:
                if net[0] in netdict:
                    nic.disconnect() #start  over here
                    nic.active(False)
                    time.sleep(1)
                    nic.active(True)
                    nic.connect(net[0], netdict[net[0]])
                    while nic.status() > network.STAT_IDLE and nic.status() != network.STAT_GOT_IP: 
                        time.sleep(1) #check again later
                    if verbose: print("connected to", str(net[0], 'utf8'), nic.ifconfig())
                    break

            ##nic.config(hostname  = "powerline_pico")
            last_status = nic.status()
            time.sleep(1) #check again later
        else:
            config =  nic.ifconfig()
            uping.ping(config[-1], count = 1)
            if verbose: print("on net:", nic.status(), nic.ifconfig())
            time.sleep(5)
            
keep_net_alive(verbose)

This seems to work.
Still have to understand what's going on here.
Is the ping important to keep the connection alive (somewhere I read something like this, it seems to me) or is it only an example of what you can do?

[mendenm]

For me, if I didn't do the ping, and left the network idle for a long time (many hours or a day), it would end up disconnected in such a way that only a power cycle would bring it back. There's probably another way around this, but the ping is so easy that I didn't spend more time figuring it out.