BG600L-M3 problems establishing PPP link

[hrm]

Hi!

I have problems setting up PPP link with BG600. I’m using Zephyr running on nrf52840 uC. If I swap the BG600 board with Ai Thinker A9 GPRS board, the PPP works reliably every time. At first I thought that the problem may be hardware related, but the board works using QIOPEN and QISEND commands. Also from time to time, the board establishes PPP link but then fails again in the subsequent attempts.

I’m not familiar with the PPP protocol and it’s hard for me to figure out where the problem really is.
Before I invoke ATD*99#, here’s the status of CGREG, CEREG and CSQ:
+CGREG: 0,1
+CEREG: 0,4
+CSQ: 17,0

and now here’s the hexdump of the PPP setup. I think the module fails in the early LCP initialization from what I can see:

bg600-ppp.txt.zip (924 Bytes)

Is there anyone who is well familiar with PPP and could suggest ways to debug the problem? Any tools for that? Do you see anything wrong with the comunication between the uC and the BG600 module? Is there any new firmware releases after BG600LM3LAR02A04 addressing similar issues?

[Stephen.Li-Q]

1. Based on your decription , I can not know the detail of your network topology . ( how to connect nrf52840 /PC and BG600L
   2 .for BG600l connect to PC ,. and make PPP connection from the PC , pls follow the below docs

Quectel_BG95&BG77&BG600L_Series_PPP_Application_Note_V1.0.pdf
https://cnquectel-my.sharepoint.com/:f:/g/personal/america-fae_quectel_com/Eh9bhvi0CxNMtR4-jAL9ZfEBMaCTqCQFz0H6_6cg8axJrA?e=8zDfef

[hrm]

I just figured the problem.
The DTR pin on my board was floating and while configuring PPP, the RF interference caused it to change levels which disconnected the data call.

AT&D0 fixed my issue

Also I should note that it’s not good practice to leave that pin floating especially if there’s trace that can act as antenna. In future designs I’ll probably also add small capacitor (1nF) close to the pin to filter unwanted RF interference.