[Original] experiences in debugging GPRS/WCDMA modules (Author: gooogleman)

By gooogleman (Www.gooogleman.comWebmaster) Time:

Experiences in debugging GPRS/WCDMA modules (by gooogleman)
Http://www.gooogleman.com/forum.php? MoD = viewthread & tid = 19095 & fromuid = 3

Yesterday, an electric power company sent the PDA back, and the 3G module exposed the problem again-often unable to connect. Once connected, the system prompts "the port is occupied ". Khan just returned a batch of antennas last week, solving the problem of "verified users" not moving-a good antenna was replaced.

For a long time, our GPRS and WCDMA both have such problems. Some machines seldom prompt "port occupied", and some frequently think that the telit 3G module is unstable, it also has some relationship with your own machine design. I also took this as a reason, or I made a conclusion to myself-this is a problem with hardware design and the 3G module itself, and I have come up with a lot of evidence: my previous GPRS and some 3G modules were relatively stable, and there were very few such tangle cases.

Yesterday, I took a returned machine and operated on it. I found an amazing rule: When the PDA was carrying a battery, it was put for one night and the next day it was able to connect to the 3G module for the first time, however, after the instance is shut down and then started, the connection fails. Or, you can unplug the battery and install the battery on the PDA for about one minute, and find that the instance can be used again, and then shut down and start again. I had no choice but to look at this terrible machine. Later I found that this rule proves the fact that the second time when the 3G module remains powered, it cannot be used normally! So I see the circuit diagram. The power supply of the GPRS/WCDMA module is from the battery through a power chip, which is controlled by the arm pin, according to the principle, the arm should be in a high-resistance state after the shutdown. Therefore, if the arm does not control the power source chip to cut off the power supply to GPRS/WCDMA, the power source chip will always work, dizzy, which not only wastes electricity, but also causes GPRS/WCDMA to work abnormally.

I added the gpio control power chip to the power supply key drive and the oempoweroff function.CodeCurrently, the GPRS/WCDMA module can be normally connected for dozens of consecutive power-on and power-off times. Finally, we have fixed this bug. The customer is already dissatisfied with our machine and will lose confidence. This time, we should have recovered some credibility.

From this case, it is sometimes easy to take it for granted. Many things are not impossible, but are not paid enough. It is not easy to make a product. In principle, the company should sell the product only when there are more tests, but the company will sell the product in large quantities after proofing. This is really unreasonable and we despise it!