MC8700 Detach problems?


We’ve been changing lately out modems from MC8780 (which run perfectly) to the new ones: MC8700. When we first encountered problem we put the blame on our hardware and revised it. It happened on double-checked device, so we put MC8700 into devel-kit and then into laptop which had embedded mini PCIe connector – nothing helped.

Problem occurs mostly during AT+CGATT=0 command, but have been spotted also during some earlier disconnect stages or even during AT+CGATT=1. We checked that our software runs right, then made another test using some Python scripts.

After issuing AT+CGATT=0 the modem just stops responding to AT commands, it just sends nothing, not even echo. It sits still until we close the AT port and open it again, sometimes hard reset is required.

Our script tries to perform following actions 100 times:
*dial-up using win32ras
*get a WWW page,
*get a file using FTP
*hang-up using win32ras

Using MC8700 it never reaches 100th time, well, to be honest, the mean number of iterations is about 15. We run those tests also on MC8780 and we completed 300 cycles without failure.

It has been suggested somewhere to use “direct ip” approach, using AT+SCACT and it did work. We repeated tests and it worked flawlessly.

Unfortunately we need dial-up interface, because we use it to measure some connection times. Does anybody have any clue what could be wrong? Any help appreciated…


I think the problem is coming from AT+CGATT.
You can simply skip doing AT+CGATT or replace it with AT+CGACT=0 if you want to sure the completation of dropping data call.

AT!SCACT instead do not involve AT+CGATT so that’s maybe the reason it works prefectly in your test.