Telstra LTE Cat-M Working on FiPy .... Just..

[timh]

@ioag

Yes I am sending AT+COPS?
But I never see True returned from isattached.
Often the send_at times out when sending AT+COPS?
Following up with something like ATI returns the output of the COPS? plus the ATI response.

[timh]

@ioag

After more testing, I am finding the following.

1. Only the first call to AT+COPS=? works, though often returns with no value, and a subsequent call say ATI will return the scan results + ATI

   lte.send_at_cmd('AT+COPS=?')
   ''
   lte.send_at_cmd('ATI')
   '\r\n+COPS: (1,"Telstra Mobile","Telstra","50501",7),,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\n+CEREG: 4\r\n'

This suggests we should be able to set a timeout on send_at_cmd
After checking isattached for a while (loop with sleep)
I check a AT+COPS again. However from then on I get errors.

>>> lte.isattached()
False
>>> lte.send_at_cmd('AT+COPS=?')
''
>>> lte.send_at_cmd('ATI')
'\r\n+COPS: ,,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\n+CEREG: 4\r\n\r\nSEQUANS 
Communications\r\nVZM20Q\r\nUEUnknown\r\n\r\nOK\r\n'
 >>> lte.send_at_cmd('ATI')
 '\r\nSEQUANS Communications\r\nVZM20Q\r\nUEUnknown\r\n\r\nOK\r\n'
 >>> lte.send_at_cmd('AT+COPS=?')
 ''
 >>> lte.send_at_cmd('AT+COPS=?')
 '\r\n+COPS: ,,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n'
 >>> lte.send_at_cmd('AT+COPS=?')
 '\r\n+COPS: ,,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n'

[nathanh]

@timh said in Telstra LTE Cat-M Working on FiPy .... Just..:

@nathanh

I am trying a few different antenna (which support 700-960) range to see if they make any difference, but so far no improvements. Will try and get something specific to Band 28.

T

That's disappointing I was really hoping that might be the cause. I am still waiting for my new antenna to arrive to test here.

@ioag said in Telstra LTE Cat-M Working on FiPy .... Just..:

@timh according to Adafruit that Antenna is purpose built for LTE Band28, cf below spec.

If you look around at places that sell that antenna (core, e14, rs etc), they regurgitate the exact same details however have no link to the supplier, documentation or any specsheet, radiation patterns or testing, in fact same sites even show a different picture but deliver that antenna (for example I ordered this part specifically https://au.rs-online.com/web/p/semiconductor-development-kit-accessories/1466433/?searchTerm=146-6433 and got the antenna above) and finally if you look at the Wieson site, you can't even find that antenna listed.

Also when it comes to antennas, companies that don't list any documentation, specifically no spec sheet or gain reports at different frequencies is an indicator of dodgy equipment. Not saying this is the case here but the warning signs I have come to learn are definitely flagging here. Just compare any info you can find on that antenna vs a more well known company: https://www.telcoantennas.com.au/site/rfi-cd7194-3g4g4gx-mobile-antenna

@timh said in Telstra LTE Cat-M Working on FiPy .... Just..:

This suggests we should be able to set a timeout on send_at_cmd
After checking isattached for a while (loop with sleep)
I check a AT+COPS again. However from then on I get errors.

Looking through the firmware on github, it looks as if there is a timeout value being used (https://github.com/pycom/pycom-micropython-sigfox/blob/master/esp32/mods/modlte.c) and any result is posted to a global response value. So if you requested two AT commands in succession with the first one timing out, the response may come back in a subsequent command. Which is what you (and I also) see when calling COPS. If you look around on the net you will see calling COPS does take a while and most raw AT command examples put a wait command as it can take a while. Ideally, Pycom should pass through to us the ability to set the timeout and, personally, I would remove the use of a "global" response variable and ensure the correct response is returned for the correct command, which I find odd how it is being done since they are usingf a queue mechanism with a shared variables which kinda defeats the purpose of the queue. Seems like IPC/threading 101...

Trying to solve what is going on here, I try and put on my House MD hat and look at the symptoms which are:

a. Can connect but appears to be random with no sure way to repeat. There appears to be no real reason why this sometimes works and sometimes doesn't. Time of day, location and signal strength to towers all seem to have no visible change on this behaviour.

b. When we do connect, is it crashes the modem after some time. Leaving the modem connected after lte.connect() and doing nothing will have the modem disconnect and/or crash in a relative short time. Sending data over a socket while connected or setting lte.disconnect() after connecting/sending a payload will keep the modem alive longer but eventually will still lose cellular connection/crash.

c. Trying to reset the modem and connect is hit and miss as well. lte.reset lte.deinit do not always work or if the modem is crashed has no effect. Reset often requires a full power on/off.

To me this points at a few potentials:
a. Bad firmware on the Sequans modem itself that is having issues talking on the LTE CAT-M network on Band 28.
b. Antenna issues that are not allowing consistent/proper radiation for the signal to work
c. Heat/circuitry issues with the Pycom or chips involved.
d. Bad Pycom firmware. (I add this here but looking through it, there does not seem to be anything obvious wrong or unusual so I don't think it is Pycom's use of the lte library, however, more access to some of the functions and their parameters would be useful).

And some of the things we can tick off are:
a. The Pycom unit is clearly able (to some extent) connect to Telstra regardless of certification
b. The Telstra LTE CAT-M network is actually functioning in the first place
c. The SIM cards are working
d. Testing in multiple locations and getting similar results would seem to indicate it is not an LTE/Band28 coverage issue

My question to @daniel @seb @jmarcelino would be, have you had any success attaching the Pycom units to a real-world LTE CAT-M network on Band 28 anywhere in the world? And is there any leverage you can put on Sequans and/or Telstra to look into this issue.

[timh]

@nathanh

Having read through the code an intersting observation is that

lte_attach sets up explicit scanning frequencies

    lte_push_at_command("AT!=\"clearscanconfig\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=3 dl-earfcn=1575\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=4 dl-earfcn=2175\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=12 dl-earfcn=5095\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=13 dl-earfcn=5230\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=20 dl-earfcn=6300\"", LTE_RX_TIMEOUT_MIN_MS);
    lte_push_at_command("AT!=\"RRC::addscanfreq band=28 dl-earfcn=9435\"", LTE_RX_TIMEOUT_MIN_MS);

Then performs

  "AT+CFUN=1"

Given a known country with only a single band it would seem that scanning all those frequencies is redundant.
However a showphys after clearing and only setting band 28 seems to never see a different state than OFF maybe it's scanning faster.

[nathanh]

@timh said in Telstra LTE Cat-M Working on FiPy .... Just..:

Given a known country with only a single band it would seem that scanning all those frequencies is redundant.
However a showphys after clearing and only setting band 28 seems to never see a different state than OFF maybe it's scanning faster.

Haha, I saw the same thing last week and had the exact same thought and did the same test with the same results. Great minds? :). I also tried playing with the dl-earfcn value but did not have any luck either.

[timh]

@nathanh Just tried the new firmware.

Some observations. The only way I can get AT+COPS=? to show Telstra network is

 >>> from network import LTE
 >>> lte = LTE()
 >>> import time
 >>> lte.send_at_cmd('AT+CGDCONT=1,"IP","telstra.m2m"')
 '\r\nOK\r\n'
 >>> lte.send_at_cmd('AT+CFUN=1')
 '\r\nOK\r\n'
 >>> lte.attach()
 >>> lte.send_at_cmd('AT+COPS=?')
 ''
 >>> lte.send_at_cmd('ATI')
 '\r\n+COPS: (1,"Telstra Mobile","Telstra","50501",7),,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\nSEQUANS Communications\r\nVZM20Q\r\n'

I have tried various other combinations but I cannot see Telstra without sending the following commands between instantiating the lte entity and calling attach

 lte.send_at_cmd('AT+CGDCONT=1,"IP","telstra.m2m"')
 lte.send_at_cmd('AT+CFUN=1')

Examples (each session has a power cycle resetting everything).

	>>> from network import LTE
	>>> import time
	>>> lte = LTE()
	>>> lte.send_at_cmd('AT+CGDCONT=1,"IP","telstra.m2m"')
	'\r\nOK\r\n'
	>>> lte.send_at_cmd('AT+CFUN=1')
	'\r\nOK\r\n'
	>>> lte.attach(band=28)
	>>> lte.send_at_cmd('AT+COPS=?')
	''
	>>> lte.send_at_cmd('ATI')
	'\r\n+COPS: (1,"Telstra Mobile","Telstra","50501",7),,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\nSEQUANS Communications\r\nVZM20Q\r\n'
	>>> lte.isattached()
	False
	>>> Disconnected. Press any key to reconnect.
	> Failed to connect (Error: Port is not open). Press any key to try again.
	Connecting on COM5...

	>>> from network import LTE
	>>> lte = LTE()
	>>> lte.attach(band=28)
	>>> lte.send_at_cmd('AT+COPS=?')
	'\r\n+COPS: ,,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\n+CEREG: 4\r\n'
	>>> Disconnected. Press any key to reconnect.
	> Failed to connect (Error: Port is not open). Press any key to try again.
	Connecting on COM5...

	>>> from network import LTE
	>>> lte = LTE()
	>>> lte.send_at_cmd('AT+CGDCONT=1,"IP","telstra.m2m"')
	'\r\nOK\r\n'
	>>> lte.attach(band=28)
	>>> lte.send_at_cmd('AT+COPS=?')
	'\r\n+COPS: ,,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\n+CEREG: 4\r\n'
	>>> Disconnected. Press any key to reconnect.
	> Failed to connect (Error: Port is not open). Press any key to try again.
	Connecting on COM5...



	>>> from network import LTE
	>>> lte = LTE()
	>>> lte.send_at_cmd('AT+CFUN=1')
	'\r\nOK\r\n'
	>>> lte.attach(band=28)
	>>> lte.send_at_cmd('AT+COPS=?')
	''
	>>> lte.send_at_cmd('ATI')
	''
	>>> lte.send_at_cmd('ATI')
	'\r\nSEQUANS Communications\r\nVZM20Q\r\nUEUnknown\r\n\r\nOK\r\n'
	>>>
	
	>>> from network import LTE
	>>> lte = LTE()
	>>> lte.send_at_cmd('AT+CGDCONT=1,"IP","telstra.m2m"')
	'\r\nOK\r\n'
	>>> lte.send_at_cmd('AT+CFUN=1')
	'\r\nOK\r\n'
	>>> lte.attach(band=28)
	>>> lte.send_at_cmd('AT+COPS=?')
	''
	>>> lte.send_at_cmd('ATI')
	'\r\n+COPS: (1,"Telstra Mobile","Telstra","50501",7),,(0,1,2,3,4),(0,1,2)\r\n\r\nOK\r\n\r\nSEQUANS Communications\r\nVZM20Q\r\n'
	>>> lte.isattached()
	False
	>>> Disconnected. Press any key to reconnect.
	> Failed to connect (Error: Port is not open). Press any key to try again.
	Connecting on COM5...

[nathanh]

@timh that is disappointing...

I am currently with clients overseas at the moment but have purchased some proper LTE antennas that have been delivered and also purchasing a separate LTE cat-m modem to compare. These will be the last things I try.

Like you I am building for commercial devices and given @administrators seem to respond to every forum thread except this one and I even had a server with a device ready for them to test/play with since my first post and they still have not gotten back to me does not instill me with confidence. If I get no luck next week I will most likely go with another micro controller or the esp32 on it's own.

[daniel]

Hello everyone,

Apologies for the delays here. We have a session with the Telstra team this week to sort this out with their help. We'll update everyone after that.

Cheers,
Daniel

[IOAg]

@daniel i have been able to connect consistently to LTE Telstra using below band settings:
lte.send_at_cmd('AT!="addscanfreq band=28 dl-earfcn=9410"')

In comparaison, latest firmware v 1.17.2.b1 is not working when I calling attach(band=28); Do you mind checking with telstra about your earfcn parameter?

[daniel]

@ioag said in Telstra LTE Cat-M Working on FiPy .... Just..:

9410

That's interesting... I'll ask Telstra. How did you come up with the value of 9410? The central value should be 9435 according to the specs...

[IOAg]

@daniel Telstra staff gave me this value to try, worked first go :)

[robert-hh]

@timh The Pycom firmware times out 10 seconds after sending a command. "AT+COPS=?" takes longer to respond. I've seen that by hooking on a pair UART/USB bridges to the link between the ESP32 and the Sequans modem. I just wanted to see what's going on there.

[John Baird]

@ioag Any chance you could share your Telstra connect code? I must be doing something wrong...
Does anyone have an update on the stability issues?