Cannot connect Thingy91 to NB-IOT or LTE-M network. Unable to load certificate due to buffer overflow

[John Buckley]

Hello,

I cannot connect Thingy91 to NB-IOT or LTE-M network. I am in the UK, so I am trying the NB-IoT with an O2 sim card. In LTE Link monitor I am unable to get a connection. LTE flashes between yellow to red.

I have tried creating a certificate on NRF cloud, but when I add the certificate, I receive the message:

at_host: Buffer overflow, dropping 'b'...

Which seems to indicate that the message is too long. As in the certificate manager, it gives the instructions:

Make sure your device runs a firmware with increased buffer to support long AT-commands.

However I am installing the default firmware. I have tried both thingy91_ltem_v0.2.2.hex and thingy91_nbiot_v0.2.2.hex, both giving the same results.

So my three questions are:

1) Do I need to load a certificate to get a connection?

2) If so, is there a compiled firmware (.hex) that allows the certificate length as an AT command by default?

3) If not, is there a template project that I can modify and compile so that I can load the certificate?

Thanks,

John

[Simon]

To start with, could you try to update to the newest modem firmware, and see if you are able to get a connection. Check out this link on how to do it.

John Buckley said:

1) Do I need to load a certificate to get a connection?

You don't need the certificates to get a connection to the network. You will need certificates to connect to nRF Cloud. If you want to connect to nRF Cloud, you only need to load the certificates if the old ones have been deleted, see this post.

John Buckley said:

2) If so, is there a compiled firmware (.hex) that allows the certificate length as an AT command by default?

Yes, you can load new certificate with thingy91_at_client_v0.2.3.hex. Can be download as part of firmware binaries found here  

John Buckley said:

3) If not, is there a template project that I can modify and compile so that I can load the certificate?

I will look into this

Also, could you provide the whole log, not only "at_host: Buffer overflow, dropping 'b'..."

Best regards,

Simon

[John Buckley]

Hello Simon,

Thank you for your reply. I think the initial problem is that the iBasis sim card does not work in the UK. I then tried a standard O2 PAYG SIM card, but I now think that I need a specific NB-IoT card for the UK. I have ordered a SIM card and if that connects, I will then try to set the certificate as above.

Thanks,

John