Does LTE work in the USA?

netskink

I have the following code:

def lte_attach():
    print("lte trying to attach")
    #lte.attach(band=13)
    lte.attach()
    while not lte.isattached():
        time.sleep(0.5)
        #print('Attaching...')
        print('Attaching...', end='')
        send_at_cmd_pretty('AT+CEREG?')         # get the System FSM

    print('**** lte attached ***********************')
    time.sleep(5)

My output is simply:

Attaching...
+CEREG: 2,4

OK

Attaching...
+CEREG: 2,4

OK

Sometimes, it will say CEREG: 2,0. I've rebooted the device, power cycled, and tried this on multiple days and its the same result. A few months ago, this same code actually worked. Nothing has changed on my end. Although at that time, I had to run this code for long periods of time before it would actually connect. I thought I was in the same situation now, but it has never resolved.

jcaron

@netskink Do you have good coverage in your area? What SIM are you using? What service (CAT-M1 or NB-IoT)? What antenna are you using? Is it connected to the right port?

netskink

@jcaron

Do you have good coverage in your area?

The signal is poor.

What SIM are you using?

It was provided to me by someone else. I believe it is a hologram sim card.

What service (CAT-M1 or NB-IoT)?

You got me. I don't know what that means. I am using the example code from the website on a pyfi. This is all that I am doing:

def lte_init():
    lte.reset()
    lte.init()

def lte_attach():
    print("lte trying to attach")
    #lte.attach(band=13)
    lte.attach()
    while not lte.isattached():
        time.sleep(0.5)
        #print('Attaching...')
        print('Attaching...', end='')
        send_at_cmd_pretty('AT+CEREG?')         # get the System FSM

    print('**** lte attached ***********************')
    time.sleep(5)


def lte_connect():
    print("lte trying to connect")
    #lte.connect(cid=3)
    lte.connect()
    while not lte.isconnected():
        time.sleep(0.5)
        print('Connecting...')

    # Now use sockets as usual...
    print('**** lte connected ***********************')
    time.sleep(5)

def do_lte():
    lte_init()
    lte_attach()
    lte_connect()

This code worked earlier. Maybe two months ago. I haven't really tested it or modified it since then.

What antenna are you using?

I don't know how to describe. It was provided to me. It appears to be this one:

https://pycom.io/product/lte-m-antenna-kit/

Gijs

Maybe check out the example here: https://docs.pycom.io/tutorials/networks/lte/. Below, there is some sort of guide on the attaching sequence. Let me know of your result!

Best,
Gijs

netskink

@Gijs As you suggested, I have tried the examples again. Here they are with my results.

From https://docs.pycom.io/tutorials/networks/lte/

Example One

Changes from original are identified with # JFD

def example_one():
    lte = LTE()
    lte.init()
    #some carriers have special requirements, check print(lte.send_at_cmd("AT+SQNCTM=?")) to see if your carrier is listed.
    #when using verizon, use 
    #lte.init(carrier=verizon)
    #when usint AT&T use, 
    #lte.init(carrier=at&t)

    #some carriers do not require an APN
    #also, check the band settings with your carrier
    #lte.attach(band=20, apn="your apn") 
    lte.attach()  #JFD Unknown 
        print("attaching..",end='')
    # JFD while not lte.isattached()
    while not lte.isattached():
        # JFD time.delay(0.25)
        utime.sleep_ms(25)
        print('.',end='')
        print(lte.send_at_cmd('AT!="fsm"'))         # get the System FSM
    print("attached!")

    lte.connect()
    print("connecting [##",end='')
    while not lte.isconnected():
        # JFD time.sleep(0.25)
        utime.sleep_ms(250)
        print('#',end='')
        #print(lte.send_at_cmd('AT!="showphy"'))
        print(lte.send_at_cmd('AT!="fsm"'))
    print("] connected!")

    # JFD Add delay
    utime.sleep_ms(250)

    # JFD print(socket.getaddrinfo('pycom.io', 80))  
    print(usocket.getaddrinfo('pycom.io', 80))  
    lte.deinit()
    #now we can safely machine.deepsleep()

The above code loops continously in the while not let.attached(): stanza. It has the following output:

SYSTEM FSM
==========
    +--------------------------+--------------------+
    |            FSM           |        STATE       |
    +--------------------------+--------------------+
    | RRC TOP FSM              |SCANNING            |
    | RRC SEARCH FSM           |WAIT_RSSI           |
    | RRC ACTIVE FSM           |NULL                |
    | PMM PLMN FSM             |ANY_WAITCELL        |
    | EMM MAIN FSM             |NULL                |
    | EMM AUTH FSM             |NULL                |
    | EMM CONN FSM             |NULL                |
    | EMM TAU FSM              |NULL                |
    | EMM TEST FSM             |NULL                |
    | ESM BEARER FSM           |BEARER_NULL         |
    | SMS MT FSM               |IDLE                |
    | SMS MO FSM               |IDLE                |
    | HP MAIN FSM              |IDLE                |
    | HP USIM FSM              |READY               |
    | HP SMS MO FSM            |IDLE                |
    | HP SMS MT FSM            |IDLE                |
    | HP CAT FSM               |IDLE                |
    +--------------------------+--------------------+

OK

Since this is a hologram code, I have also tried with the following modification to the example: lte.attach(apn="hologram") . In this case, it worked!!! (Possibly it also helped that during the time letting it run until lockup I also physically straightened the antenna fingers. They were curled so I put a sticky on each side of the fingers to hold straight.) The status settings are as below. In the all caps case, its the state when the code locked up.:

RRC TOP FSM: [CONNECTING], Scanning, Syncing, Camped, Camping,
RRC SEARCH FSM: [CAMPED], Wait RSSI, Wait Cell ID, Wait SIBX, Camped_Any,
RRC ACTIVE FSM: [Wait_SMC], Wait RSSI, Wait Cell ID, Wait SIBX, Camped_Any,
PMM PLMN FSM: [NORM CAMPED]
EMM MAIN FSM: [DEREG REGISTERING]
EMM AUTH FSM NULL
EMM CONN FSM [AS_ESTABLISHING]
EMM TAU FSM [NULL]
EMM TEST FSM [NULL]
ESM BEARER FSM [BEARER NULL PENDING ACTIVE]
SMS MT FSM [IDLE]
SMS MO FSM [IDLE]
HP MAIN FSM [IDLE]
HP USIM FSM [READY]
HP SMS NO FSM [IDLE]
HP SMS MT FSM [IDLE]
HP CAT FSM [IDLE]

What are these settings? Any references for the ignorant? I'm guessing FSM is finite state machine and these are possible states.

Afterwards, this happened at end.

[(2, 1, 0, '', ('18.195.176.111', 80))]

Many thanks.

netskink

Just to confirm this lockup has happened more than once.

+--------------------------+--------------------+
|            FSM           |        STATE       |
+--------------------------+--------------------+
| RRC TOP FSM              |CONNECTED           |
| RRC SEARCH FSM           |CAMPED              |
| RRC ACTIVE FSM           |CONNECTED           |
| PMM PLMN FSM             |NORM_CAMPED         |
| EMM MAIN FSM             |REGISTERED_INIT     |
| EMM AUTH FSM             |KASME_DEFINED       |
| EMM CONN FSM             |AS_ESTABLISHED      |
| EMM TAU FSM              |NULL                |
| EMM TEST FSM             |NULL                |
| ESM BEARER FSM           |BEARER_NULL_PENDING_ACTIVE|
| SMS MT FSM               |IDLE                |
| SMS MO FSM               |IDLE                |
| HP MAIN FSM              |IDLE                |
| HP USIM FSM              |READY               |
| HP SMS MO FSM            |IDLE                |
| HP SMS MT FSM            |IDLE                |
| HP CAT FSM               |IDLE                |
+--------------------------+--------------------+

Gijs

This last FSM report seems to have connected perfectly fine? The last message:

[(2, 1, 0, '', ('18.195.176.111', 80))]

Is the output of the socket.getaddrinfo() meaning the modem is able to do DNS lookup!
Best,
Gijs

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