GPy with Hologram.io SIM



  • Should the Pycom GPy using a Hologram SIM card work today with LTE CAT-M1 in the US (Georgia)?

    I’m trying to run the example app (updated on 4/16/18) listed below and the program never gets past the “attach to cell network” stage.

    import pycom
    import socket
    import ssl
    import sys
    import time
    from network import LTE
    
    BLACK = 0x000000
    WHITE = 0xFFFFFF
    RED = 0xFF0000
    GREEN = 0x00FF00
    BLUE = 0x0000FF
    YELLOW = 0xFFFF00
    
    # send AT command to modem and return response as list
    def at(cmd):
        print("modem command: {}".format(cmd))
        r = lte.send_at_cmd(cmd).split('\r\n')
        r = list(filter(None, r))
        print("response={}".format(r))
        return r
    
    def blink(rgb, n):
        for i in range(n):
            pycom.rgbled(rgb)
            time.sleep(0.25)
            pycom.rgbled(BLACK)
            time.sleep(0.1)
    
    #####################################################################
    print("CAT M1 Test - V0.4 - 4/15/18")
    
    print("disable MicroPython control of LED")
    pycom.heartbeat(False)
    pycom.rgbled(WHITE)
    
    print("instantiate LTE object")
    lte = LTE(carrier="verizon")
    print("delay 4 secs")
    time.sleep(4.0)
    
    if lte.isattached():
        print("LTE was already attached, disconnecting...")
        lte.disconnect()
        lte.detach()
        print("resetting modem...")
        lte.reset()
        print("delay 5 secs")
        time.sleep(5.0)
    
    # enable network registration and location information, unsolicited result code
    at('AT+CEREG=2')
    
    print("full functionality level")
    at('AT+CFUN=1')
    time.sleep(1.0)
    
    # using Hologram SIM
    at('AT+CGDCONT=1,"IP","hologram"')
    
    print("attempt to attach cell modem to base station...")
    # lte.attach()  # do not use attach with custom init for Hologram SIM
    
    i = 0
    while True:
        # get EPS Network Registration Status:
        # +CEREG: <stat>[,[<tac>],[<ci>],[<AcT>]]
        # <tac> values:
        # 0 - not registered
        # 1 - registered, home network
        # 2 - not registered, but searching...
        # 3 - registration denied
        # 4 - unknown (out of E-UTRAN coverage)
        # 5 - registered, roaming
        r = at('AT+CEREG?')
        r0 = r[0]  # +CREG: 2,<tac>
        r0x = r0.split(',')     # ['+CREG: 2',<tac>]
        tac = int(r0x[1])       # 0..5
        print("tac={}".format(tac))
    
        if lte.isattached():
            print("Modem attached (isattached() function worked)!!!")
            break
    
        if (tac==1) or (tac==5):
            print("Modem attached!!!")
            break
    
        i = i + 1
        print("not attached: {} secs".format(i))
    
        if (tac != 0):
            blink(BLUE, tac)
        else:
            blink(RED, 1)
    
        time.sleep(1)
    
    print("connect: start a data session and obtain an IP address")
    lte.connect()
    i = 0
    while not lte.isconnected():
        i = i + 1
        print("not connected: {}".format(i))
        blink(GREEN, 1)
        time.sleep(1.0)
    
    pycom.rgbled(BLUE)
    
    s = socket.socket()
    s = ssl.wrap_socket(s)
    s.connect(socket.getaddrinfo('www.google.com', 443)[0][-1])
    s.send(b"GET / HTTP/1.0\r\n\r\n")
    print(s.recv(4096))
    s.close()
    
    lte.disconnect()
    lte.dettach()
    
    # end of test, Red LED
    print("end of test")
    
    while True:
        blink(YELLOW,1)
        time.sleep(1.0)
    


  • @wgtthompson I found this to be the case as well. Just hung at the lte instantiation until i started resetting it after declaring it even if using the same carrier as before.



  • @wgtthompson

    I do not believe the source code that you see in github is the code we are actually running currently. The reason I say that is I noticed extensive changes made to the modlte.c code a few weeks ago, and I have not seen any indication that an update has been made available to download.



  • I've noticed that setting a carrier other than verizon such as LTE(carrier='at&t') or LTE(carrier='standard') results in my modem not being able to connect to any carrier, ever. Setting the carrier back to verizon does not fix it. A reset does not fix it. A power cycle does not fix it. The only way I've found that fixes this problem is to re-flash the modem firmware.

    I really don't see why this is even a constructor argument. Looking at the source code for modlte.c, it looks like it is setting the test conformance mode using the AT command AT+SQNCTM in the INIT phase of the modem. The AT manual for this modem specifically cautions for this command that "The change will be effective after the device’s reboot." I don't see a device reboot occurring in the code. It looks like the carrier argument is modifying a modem setting that won't take effect until a modem reboot.

    This is an undocumented part of the LTE API.

    '''
    Changing carrier from the current setting in the modem.  The carrier value is stored through power cycle by the modem.  If the carrier setting is changed then a reset needs to follow for the value to take effect.
    '''
    lte = LTE(carrier=NEW_VALUE)
    lte.reset()  #  cycle modem for new carrier to take effect
    
    #  ... now use the object as normal...
    


  • @tlanier Yes, I used lte = LTE(carrier='verizon') and can only connect to the local AT&T service.



  • @wgtthompson

    To get the program to work, I had to set the carrier to "verizon" in the LTE function call

    lte = LTE(carrier="verizon")

    Hologram states that their SIM works with multiple carriers. I don't understand how that works if I'm having to specify the carrier in the initialization.

    We need Pycom and Hologram to clarify what is the correct method to initialize the LTE object and what carriers can we expect to connect to.



  • The example (dated 4/20/2018) works for me when the modem connects to an AT&T service. It never works if the modem decides to connect to a Verizon service. I am using a GPy and a Hologram SIM.

    I can tell which service because the Hologram dashboard shows the service for a specific session.

    For AT&T, the modem waits to attach for about 10-20 sec. While waiting to attach, the signal quality starts at +CSQ: 99,99 (RSSI known) and transitions to +CSQ: 20,99 (RSSi known). The registration state starts at +CEREG: 2,0 and changes to +CEREG: 2,2. The modem then transitions to attached, then connects, and works like a charm.

    For Verizon, the modem never attaches (I let it loop for an hour once). While waiting to attach, the signal quality will oscillate between +CSQ: 99,99 (RSSI unknown) to +CSQ: 20,99 (RSSi known) roughly ever loop. The registration state starts at +CEREG: 2,0 and then changes to +CEREG: 2,4

    Anybody got thoughts?

    Note: the example I used has date 4/20/2018 in the code and is posted by @tlanier. I did not use the 4/15/2018 version in his/her original post.



  • @rwall

    I did not experience any lock ups during the trip. Basically I would occasionally plug the unit into the car's USB port and run the test program posted on 4/20/18. I experienced the lock ups when developing the test program trying to find something that would work. I think the exception handling code added helped. As soon as we determine that coverage is good enough, I will do more extensive programming with the unit. Also I was hoping to get some feedback as to when the code changes to the cell connectivity code made on GitHub would be available for download and testing.



  • @tlanier, thanks for the update. Do the results from your road trip mean that your system is no longer locking up on the LTE(carrier="verizon") line? If yes, can you share how it was resolved?



  • @rwall

    Last weekend I drove the device from LaGrange, GA to Fairhope, AL (about 270 miles) . During the trip I spot checked CAT M1 connectivity. It worked everywhere except when I reached Fairhope where it did not work even though I had 3-4 bars on my cell phone (which also uses Verizon). We are still looking for a coverage map from the carrier detailing where CAT M1 coverage should be expected.



  • @rwall If it requires that we do something other than set the APN, I assume that the development process baked in some special magic to get around some restriction on the Verizon side of things (understandable if it was due to the relatively new Sequans chipset). I would be curious if any other SIMs have been tried other than ours and Verizon's. For now, I'm left at the same stage as others of "waiting for updates from the LTE team".

    I had missed Nathan's question about rebuilding the firmware. I did not, I simply used the latest block of code that tlanier had posted. I verified it connected to the Verizon tower and to our cloud and then got pulled away onto something else.

    Fun new feature on our dashboard, you can see live usage data and tower location for pro plan stuff.



  • Has there been any additional progress on this issue?

    If not, is it possibly due to carrier="verizon" and using a hologram SIM effectively being mutually exclusive (emphasis on “effectively”).

    My understanding is that the carrier assignment optimizes the modem configuration for operation on a specific cellular network (Verizon in this case). However, operating on the Verizon network as a Verizon customer vs operating on their network through a MVNO may be very different. The most obvious is being on a home network vs roaming. In addition to functional implications, are there additional constraints based on Hologram’s contractual relationship with Verizon that may be playing a role in this issue? If I recall correctly from an old Hologram discussion, network operators like Verizon impose constraints on VMNO users such as requiring different timeouts on data connections.



  • @nathanh

    Question: did you rebuild your firmware from the changes just made to the code on Github?

    No, that's why I asked the questions:

    • When can the next update be expected?

    • How will we be notified that the update is available (the web site just has a link to the update program with no version number displayed)?



  • @chrisgammell said in GPy with Hologram.io SIM:

    I verified it's working on mine as well, thank you for sharing the code

    Out of curiosity, did you rebuild your firmware from the changes just made to the code on Github?



  • @tlanier I have made the same observation about the unit locking up, I am using the WDT to take care of that, hoping that they will solve the issue in the near future. It does not happen that often, see my other post : https://forum.pycom.io/topic/3073/lte-analysis-of-connectivity . Glad to see you got it working in the end!



  • @tlanier

    The program is now connecting to google.com successfully. I'm still having trouble with the unit locking up on the LTE(carrier="verizon") line at times. The chip/development environment gets in a crazy mode where I have to reset/power down/restart Visual Studio Code in unknown combinations to regain control of the chip.

    The Hologram.io dashboard is TERRIFIC!!! You can see data usage and the actual data that passes across the network. I love it!!!

    import pycom
    import socket
    import ssl
    import sys
    import time
    from network import LTE
    
    BLACK = 0x000000
    WHITE = 0xFFFFFF
    RED = 0xFF0000
    GREEN = 0x00FF00
    BLUE = 0x0000FF
    YELLOW = 0xFFFF00
    
    # send AT command to modem and return response as list
    def at(cmd):
        print("modem command: {}".format(cmd))
        r = lte.send_at_cmd(cmd).split('\r\n')
        r = list(filter(None, r))
        print("response={}".format(r))
        return r
    
    def blink(rgb, n):
        for i in range(n):
            pycom.rgbled(rgb)
            time.sleep(0.25)
            pycom.rgbled(BLACK)
            time.sleep(0.1)
    
    #####################################################################
    print("CAT M1 Test - V0.6 - 4/20/18")
    
    # input("")
    # r = input("Enter anything to abort...")  # allow opportunity to stop program
    # if r != "":
    #    sys.exit(0)
    
    print("disable MicroPython control of LED")
    pycom.heartbeat(False)
    pycom.rgbled(WHITE)
    
    print("instantiate LTE object")
    lte = LTE(carrier="verizon")
    print("delay 4 secs")
    time.sleep(4.0)
    
    print("reset modem")
    try:
        lte.reset()
    except:
        print("Exception during reset")
        
    print("delay 5 secs")
    time.sleep(5.0)
    
    if lte.isattached():
        try:
            print("LTE was already attached, disconnecting...")
            if lte.isconnected():
                print("disconnect")
                lte.disconnect()
        except:
            print("Exception during disconnect")
        
        try:
            if lte.isattached():
                print("detach")
                lte.dettach()
        except:
            print("Exception during dettach")
    
        try:
            print("resetting modem...")
            lte.reset()
        except:
            print("Exception during reset")
    
        print("delay 5 secs")
        time.sleep(5.0)
    
    # enable network registration and location information, unsolicited result code
    at('AT+CEREG=2')
    
    # print("full functionality level")
    at('AT+CFUN=1')
    time.sleep(1.0)
    
    # using Hologram SIM
    at('AT+CGDCONT=1,"IP","hologram"')
    
    print("attempt to attach cell modem to base station...")
    # lte.attach()  # do not use attach with custom init for Hologram SIM
    
    at("ATI")
    time.sleep(2.0)
    
    i = 0
    while lte.isattached() == False:
        # get EPS Network Registration Status:
        # +CEREG: <stat>[,[<tac>],[<ci>],[<AcT>]]
        # <tac> values:
        # 0 - not registered
        # 1 - registered, home network
        # 2 - not registered, but searching...
        # 3 - registration denied
        # 4 - unknown (out of E-UTRAN coverage)
        # 5 - registered, roaming
        r = at('AT+CEREG?')
        try:
            r0 = r[0]  # +CREG: 2,<tac>
            r0x = r0.split(',')     # ['+CREG: 2',<tac>]
            tac = int(r0x[1])       # 0..5
            print("tac={}".format(tac))
        except IndexError:
            tac = 0
            print("Index Error!!!")
    
        # get signal strength
        # +CSQ: <rssi>,<ber>
        # <rssi>: 0..31, 99-unknown
        r = at('AT+CSQ')
    
        # extended error report
        # r = at('AT+CEER')
        
        # if lte.isattached():
        #    print("Modem attached (isattached() function worked)!!!")
        #    break
    
        # if (tac==1) or (tac==5):
        #    print("Modem attached!!!")
        #    break
    
        i = i + 5
        print("not attached: {} secs".format(i))
    
        if (tac != 0):
            blink(BLUE, tac)
        else:
            blink(RED, 5)
    
        time.sleep(2)
    
    at('AT+CEREG?')
    print("connect: start a data session and obtain an IP address")
    lte.connect(cid=3)
    i = 0
    while not lte.isconnected():
        i = i + 1
        print("not connected: {}".format(i))
        blink(GREEN, 1)
        time.sleep(1.0)
    
    print("connected!!!")
    pycom.rgbled(BLUE)
    
    s = socket.socket()
    s = ssl.wrap_socket(s)
    print("get www.google.com address")
    addr = socket.getaddrinfo('www.google.com', 443)
    print(addr)
    print("connect to {}".format(addr[0][-1]))
    s.connect(addr[0][-1])
    print("GET 50 bytes from google")
    s.send(b"GET / HTTP/1.0\r\n\r\n")
    print(s.recv(50))   # receive 50 bytes
    print("close socket")
    s.close()
    
    try:
        lte.disconnect()
    except:
        print("Exception during disconnect")
    
    try:
        lte.dettach()
    except:
        print("Exception during dettach")
    
    # end of test, Red LED
    print("end of test")
    
    while True:
        blink(GREEN,5)
        time.sleep(1.0)
    
    


  • @chrisgammell

    It WORKED!!!

    The problem I'm having now is after I run the program once successfully the program will hang in the "lte=LTE(carrier="verizon") line at the start of the program. Unfortunately you can't reset the modem without instantiating the LTE object and instantiating the object is what gets hung up. There needs to be some command to say let's start all over and reset everything.



  • @tlanier Could you define "Crash"? Like did the REPL return? No, it's still stuck at the "end of test" message like in that image. But if I CTRL+C, I'm able to escape to the REPL.



  • @chrisgammell

    Were you able to download data from google or did it crash?

    I'm waiting my mandatory 180 secs to post on the forum again. There's got to be a better way to prevent SPAM.



  • @tlanier said in GPy with Hologram.io SIM:

    Attach/Connect Success!!!

    Awesome!

    I verified it's working on mine as well, thank you for sharing the code

    0_1524238255161_Screenshot 2018-04-20 10.28.56.png


 

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