Sophomore time bought a MP3, has been used to the university, but for some time because of lost in the cupboard behind thought disappeared, so later changed a few MP3, then accidentally found this MP3, but found a lot of problems, today again to give a try, copy song no problem, But the song copy and then MP3 playlist inside unexpectedly let the song list, I guess this MP3 is completely flutter street, and then initiation of the idea of dismantling it, after all, I have done hardware, so can be a little analysis of this MP3 work principle, the following is my disassembly analysis.
The internal structure diagram looks like this
The most important of these are two parts, CPU and Flash
。 The following detailed analysis of the CPU,CPU use of the nano-core micro-chip, because the core micro is the best domestic chip, and the company is in the opposite of our company, so I am very interested in the micro-core of Rui, I went to the Rui-core micro of the official website to check the parameters of this chip:
Below I give you analysis of the meaning of the above parameters, the first is the kernel, the core is arm Cortex M3 Core, you can understand as a processor architecture, and I used the STM32 chip core is the same, the core of the chip's advantage is cheap, functional structure is very rich, Can be very good to meet the needs of ordinary embedded products, the main frequency of 100M, this value is of course the higher the better, we run the program is followed by this frequency in the walk, the higher the frequency of the program to run faster, but for the product this need to strictly control the cost of things, the requirements are the lowest cost, performance can be met, 100M speed has been able to support audio decoding, but the video support may not be too good, low resolution screen can still be able to carry, such as the introduction of single-chip 51 chips commonly used, the main frequency is 12M, high distribution version may be higher. Again come is the storage, where the RAM is put in the program, we often say that the memory of the notebook 4GB or 8GB, said that the ram, like the notebook RAM is outside the CPU, so can be replaced and added, but for the embedded products, in order to meet the product portability and thin demand, To make things as small as possible, and embedded products need RAM is not as large as the computer, so most of the RAM integrated into the CPU, two kinds of RAM plus 224KB, which is already very large, after all, the use of μcos2 such an operating system, the size of the program is only dozens of KB. RAM is a volatile type of storage, that is, after the power loss, the contents of the store will be gone, you may ask my MP3 there will always be no electricity, then I do not have power when the power of the MP3 can also use, this is to talk about nor flash and NAND flash, this is the place to put the program, After the power is not gone, the above icon does not indicate where nor flash and NAND flash is placed, is integrated in the internal CPU or through the circuit external connection, but it is certainly supported, the general program is stored in nor flash or NAND flash inside, If the NOR Flash program can run directly inside, but because nor flash may have a bit reversal, so the reliability is not high, if the use of NAND flash, the system will be used to copy the program into RAM, and then began to run the system.
The bottom line also shows that the CPU supports the operating system Rkos, the full name is Rockchip operation system, is the core micro-operating system, I understand the Internet, is the core of the micro-research and development of the embedded operating system, for the core micro chip provides a good support, For the operating system, we are more familiar with is windows, we use the computer is, we may be surprised, the computer and MP3 look bad, how to use the operating system, in fact, for the operating system this thing, we do not have to think it is mysterious, The operating system is actually to provide us with a software operating environment, a hardware interface, so that we want to run the program on the above we can not know how to operate the hardware, as long as the operating system under the framework of the program can be, greatly facilitate the development of our software, Windows is a popular one has the advantage is that it provides a good graphical interface, we open the computer to see is, blue sky and white clouds, very friendly, let us use very happy, plus a lot of development software such as QQ, Weibo, etc., these software is for Windows development, So it can only be run on a computer with Windows, which makes us more and more inseparable from the Windows computer. and MP3 use of the operating system for the embedded product development of the operating system, do not need to provide a good look at the graphical interface, just to be able to complete simple play songs and other operations can be, so it is very small, can realize the function is relatively simple, but it is also called the operating system, the so-called Rkos is this kind of, And another popular μcos2 very much like, μcos2 function is very rich and stability and reliability have experienced the proof of practice, so in the world is very popular, as for Rkos I understand, it's a lot of mechanism and μcos2 is very similar, but most is for the core micro-chip optimization of their own, So it doesn't get popular. From the operation of the MP3 can not see what operating system, but it is sure to use the operating system, because this MP3 support multi-tasking operations, such as when you play music can read the ebook, you can view the playlist, edit the list, since Rui Core Micro has developed operating system, So the use of Rkos should not run, many of the earlier MP3 do not support and use the operating system, so the use is very inefficient, such as you want to view the playlist when you have to tentatively play the current music, it is not possible to watch the E-book while playing music. At that time MP3 already very cheap, dozens of dollars can make one, but my this MP3 spent 125 of my ocean, I fancy one reason is that its operation and dozens of Yuan MP3 not the same, although I do not know what the chip operating system.
Then look at the flash chip, this is the place where you put the copy song and put MP3 program, we generally say your MP3 a few G said is this meaning, this MP3 specification is 2GB but if you use the computer to view the size, you see certainly only 1.7 1.8G appearance, said 2G? Here are two reasons, one is the program took up a part, is put into the operating system, just like your hard disk to score a disk dedicated to the Windows operating system, and the inside of the things can not be deleted, if you delete those files, that one day your computer even boot will not boot. MP3 is also the reason, need to open an area in Flash to put the operating system. Another reason is that the computer calculates the capacity of the way and manufacturers to produce flash computing capacity in a different way, the standard calculation is 1GB=1024MB 1mb=1024kb 1kb=1024b, that is, the standard capacity is calculated according to 1024, but the manufacturers in order to calculate the convenience, Directly according to the 1000 binary calculation, so the product above the nominal capacity is certainly greater than the computer calculated capacity. and in order to separate the program storage and data storage (your songs), so that the program more secure, also in the middle of the program and the song to open a physical interval, this part of the shield off, combined with the above several reasons, so that the computer display capacity is less than the nominal capacity of the product, the capacity of the phone is also a reason, Never seen a 16GB mobile phone to a computer to show that your phone capacity of 16GB.
MP3 the internal structure of the more obvious there is a FM module, called RDA5807, for the radio function, from the picture just see, this module and MP3 other modules is independent, that is, as long as the MP3 to it to power its own can work, then MP3 to read its pin voltage value, This voltage value is converted into a digital amount that can be processed by the MP3 and then processed by the OP amp to output the sound of the headset. We're surrounded by all kinds of signals, and you're going to read these signals. What do you mean you have to know the format to get the stuff out of it, we can simply take these signals as a wave, where the waves have low, high places in high places, 1, low places that represent 0, The space is full of these 010110 signals, if you do not know the format of the signal encoding, then these signals do not make any sense to you, so if you want to get the information contained in these signals, you need to have a special device area to receive and modulation, the equivalent of the translation of our language, We can not understand the language translated into the language that we hear, RDA5807 is specialized in this kind of thing, it can receive and modulate the FM signal in the space, so-called FM signal, you just need to know that it is a signal format is enough. Some mobile phones also have the function of FM, there are two main ways to achieve, one is in the hand with the FM module like RDA5807, another implementation is to do this module tight CPU inside, the latter is now the majority of mobile phone implementation, mainly to meet the needs of mobile phone miniaturization, After all, the space inside the phone is also a small amount of gold, can save a little space is a bit.
The back of the MP3 is a small lithium-ion battery, which is provided by a Shenzhen company called HuanYu Technology. The input voltage is 3.7V, the capacity is unknown, but from the personal use, this MP3 is very good, the normal use of strength to listen to a one weeks enough, especially to my surprise is that it has no power loss of basic, you may have such experience, cell phone or battery after the electricity if not used, over a period of time the battery will be less or even Disappeared, why will not see, there are two possible reasons, one is the cause of the internal battery, this is the reason for the manufacturers, the other is the reason for the appliance itself, for example, after the shutdown of some parts of the internal circuit is still connected, the continued weak consumption of electricity, although very slow, but the time is long enough or can be exhausted, And this MP3 surprised me is that in the Senior High college entrance examination after the end of throwing one side no longer listen to the song, freshman that will be picked up again when the boot, surprised to find as much as possible two grid of power, so that this MP3 "power-off" ability is very amazing. As for the battery voltage why is 3.7V instead of 4V to take the whole, this is related to electronic products, after a lot of practice has proved that in this voltage can not only meet the use of the circuit, but also to minimize the power consumption, so we agreed to produce the product as far as possible to design in this voltage work, so with the whole number does not matter, like The use of a crystal oscillator frequency is 11.0592Mhz, is calculated in order to maximize the need to meet the convenience of computing, another electronic product is often used voltage is 5V, a lot of cell phone battery is 5V.
This MP3 uses a normal two-color LCD screen, the use of the method is very simple, while the manufacturer of this product will provide drivers, driver is a program, through this program you can use it, I personally use a liquid crystal called 1602, need to display something on it, As long as the corresponding command can be sent, the general display of this kind of things need to consume a lot of CPU resources, so the simpler the display screen, the less color, the less CPU resources needed, such as Rui-core micro This can support 320* The CPU of the 240 screen (which is the screen of most phones two years ago) shows enough of a low-end screen.
The above is my analysis of the internal structure of this MP3, the price of these modules plus a resistor capacitor and other discrete components, if the production, the cost is probably only 60 yuan is enough, and I bought 125, to remove the profit of the dealer, Taiwan Electric technology to do this MP3 at least to earn a dozens of yuan, which is quite high profit.
To personal software and hardware strength, as long as there is enough time, to make a music can play the MP3 is enough, as for the rich features, sound quality, which involves many areas of the problem, temporarily still do not understand.
Now many mobile phone manufacturers are promoting their phone's sound quality how, take out a lot of parameters, for these phenomena my point of view there are a few, one is how the sound quality is very subjective things, different people on the same phone with the sound quality of the view may vary greatly, and then there is audio decoding and ordinary data processing is not the same, Therefore, although the general CPU has audio decoding ability, but after all, it is not as special audio decoding chip, so long as your phone does not have independent audio decoding chip can not speak of the sound quality of the phone is much better, the most important point is the headset, generally the device can play music is called the front end, the headset is called the back end, The front-end can only guarantee the original sound quality, and we finally hear the voice through the headphones, although the front-end each has a difference, but the gap between each other is not big, just like the Apple phone never dare to promote their sound quality is how ahead of others, so a good headset is far more important than a good player, Only say that the sound quality of the phone is much better than the need to use what headphones propaganda are bullying, with my side is dozens of dollars to stall the goods of the headphones, the sound quality of the phone for them is meaningless.
The above is my disassembly MP3 analysis and my understanding of the sound quality, a little humble opinion, please light spray, the last tribute to the spirit of craftsmen!
"Science articles" My MP3 disassembly analysis
