MC55 debugging problems

Recently, I am working on the MC55 module project. I think we should summarize some problems. At the beginning of preparation, I felt that the difficulty was not small, mainly because there was very little introduction to MC55 hardware on the Internet. Basically, it was software, and there was no way to do it. I had to follow the example given by hardware interface description, as a result, the project was actually started. This also gave us some inspiration. Don't do any projects and always want to find the ready-made items on the Internet. In fact, there is nothing at all, currently, all the ready-made items are derived from the module information provided by the official website. Therefore, it is best to first look at datasheet to get in touch with a new thing, which will be helpful for later development. By the way, I would like to practice English! I 've been working on this module for almost a month. There are other things in the middle. Now, simple functions are basically implemented, and there is no problem with GPRS and Chinese text messages, but now there is a problem. After each startup, the AT command cannot be used to shut down. The module will be restarted automatically once it is shut down, unless the PIN is configured again according to the startup sequence before shutdown, I don't know why. I'm searching ......