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i am now using lwip-1.4.1 and the modem is SIM900. I met with some trouble during NCP. Here is the data exchanged between the SIM900 and the MCU.

SEND: 7E FF 7D 23 C0 21 7D 21 7D 21 7D 20 7D 34 7D 22 7D 26 7D 20 7D 20 7D 20 7D 20 7D 25 7D 26 7D 2B 3F 7D 38 7D 3C 7D 27 7D 22 7D 28 7D 22 65 D9 7E //LCP

RECEIVE: 7E FF 7D 23 C0 21 7D 21 7D 21 7D 20 7D 2E 7D 22 7D 26 7D 20 7D 2A 7D 20 7D 20 7D 23 7D 24 C0 23 F3 4D 7E //LCP

RECEIVE: 7E FF 7D 23 C0 21 7D 24 7D 21 7D 20 7D 2E 7D 25 7D 26 7D 2B 3F 7D 38 7D 3C 7D 27 7D 22 7D 28 7D 22 9C B5 7E //LCP

SEND: 7E FF 7D 23 C0 21 7D 22 7D 21 7D 20 7D 2E 7D 22 7D 26 7D 20 7D 2A 7D 20 7D 20 7D 23 7D 24 C0 23 CD CE 7E //LCP

SEND: 7E FF 7D 23 C0 21 7D 21 7D 22 7D 20 7D 2A 7D 22 7D 26 7D 20 7D 20 7D 20 7D 20 5F AD 7E //LCP

RECEIVE: 7E FF 7D 23 C0 21 7D 22 7D 22 7D 20 7D 2A 7D 22 7D 26 7D 20 7D 20 7D 20 7D 20 36 D9 7E //LCP

SEND: 7E FF 03 C0 23 01 01 00 0E 04 6E 6F 6E 65 04 6E 6F 6E 65 DE 60 7E //PAP

RECEIVE: 7E FF 03 C0 23 02 01 00 0D 08 4C 6F 67 69 6E 20 4F 4B 67 DC 7E //PAP

SEND: 7E FF 03 80 21 01 01 00 16 03 06 00 00 00 00 81 06 00 00 00 00 83 06 00 00 00 00 6E DB 7E // IPCP

Then nothing happened...

The LCP negotiation is successful, and i have done the PAP authentication. The problem is that after sending the IPCP request the GPRS modem does not reply the IP address. However, the modem is still in GPRS state, in other words, GPRS does not send me the terminate request.

liangqiseu
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1 Answers1

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Now i have solved the problem. I got the IP address when i used another modem SIM808. The original modem itself is something wrong and i have no idea how to solve it. Maybe i did wrong settings and it can be fixed using AT commands.

liangqiseu
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