<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> </head> <body> First of all, thank you for the instant answer :-) See comments below. <blockquote type="cite" cite="mid:250df31cf1adf33ec988d348b00fea921b380174.camel@redhat.com"> <blockquote type="cite"> <pre class="moz-quote-pre" wrap="">Hi there, I got a Telit LE910C1-EU attached to an embedded device, using ModemManager 1.19.0 (main branch, 2 commits behind) and libmbim 1.27.3 (main branch, 1 commit behind). Linux Kernel is v5.12. I was able connect successfully to an LTE network using both PPP (USB profile 0x1201, 3 AT ports) and MBIM (USB profile 0x1252, MBIM + 2AT ports). Both configurations seem to work -- I was able to ping a server using those interfaces. But there are some inconsistencies that I see: * While PPP shows a signal quality of 85%, MBIM only shows between 9 and 19 % signal quality. (When I use a AT+CSQ command in MBIM mode, the result is 20 which is in the middle of the range, so I that should be more than 20%) </pre> </blockquote> <pre class="moz-quote-pre" wrap=""> AT+CSQ and MBIM are different ways of measuring, so it depends on what the numbers you get are. Are you able to run mbimcli's "query-signal- state" option on the device? What do you see? What is the raw value from CSQ?</pre> </blockquote> <ul> <li>CSQ gives a value of 20, which maps to -73 dBm according to the documenation. </li> <li>The MBIM command returns a value of 3 for the rssi, which maps to -117 dBm according to the MBIM spec (which matches the 9% I see). </li> <li>I also checked the CIND command, that gives an rssi value of 3 as well, but here the range is 0 to 5, so indicating -68dBm. </li> </ul> <blockquote type="cite" cite="mid:250df31cf1adf33ec988d348b00fea921b380174.camel@redhat.com"> <pre class="moz-quote-pre" wrap="">In the end, it may just be a difference in how the firmware calculates and reports the value. </pre> </blockquote> To me, that looks a little bit like its a bug in the MBIM implementation in the modem: The returned the rssi in the wrong scaling when using MBIM (Just guessing....) <blockquote type="cite" cite="mid:250df31cf1adf33ec988d348b00fea921b380174.camel@redhat.com"> <blockquote type="cite"> <pre class="moz-quote-pre" wrap=""> * While PPP does not show any sim lock, MBIM shows a SimPin2 lock (although we are connected). </pre> </blockquote> <pre class="moz-quote-pre" wrap=""> This is normal, the PIN2 lock controls stuff that isn't necessary for normal operation.</pre> </blockquote> That is good, so I can ignore it. Is that PIN2 lock something specific to MBIM? Or is it just again that the implementation differs from PPP to MBIM? <blockquote type="cite" cite="mid:250df31cf1adf33ec988d348b00fea921b380174.camel@redhat.com">[...] <pre class="moz-quote-pre" wrap=""> * What limitations do I get when I use PPP instead MBIM? </pre> <pre class="moz-quote-pre" wrap=""> Mostly speed. PPP will be pretty bandwidth limited and you won't be able to achieve anywhere near full LTE speeds without MBIM. MBIM is also typically more reliable than AT+PPP since it talks to the modem more directly and the control path is simpler.</pre> </blockquote> Ok, that matches my expectations. Thank you! <blockquote type="cite" cite="mid:250df31cf1adf33ec988d348b00fea921b380174.camel@redhat.com"> <pre class="moz-quote-pre" wrap=""> Dan </pre> </blockquote> Uli </body> </html>