CN101968724A

CN101968724A - Method for storing and deleting data of SD card by using embedded ARM processor

Info

Publication number: CN101968724A
Application number: CN 201010532108
Authority: CN
Inventors: 赵祥模; 惠飞; 余腾; 史昕; 杨澜; 雷涛
Original assignee: Changan University
Current assignee: Changan University
Priority date: 2010-11-04
Filing date: 2010-11-04
Publication date: 2011-02-09
Anticipated expiration: 2030-11-04
Also published as: CN101968724B

Abstract

The invention discloses a method for storing and deleting data of a secure digital (SD) card by using an embedded advanced RISC machines (ARM) processor. The data is quantitatively or regularly stored and quickly deleted by a cache and a timer on an ARM-based data acquisition system. According to the characteristic of real-time data acquisition and data storage and deletion application, data operation with high randomness and burstiness is written into the SD card in a fixed size or fixed time mode through the cache and the timer, and a judgment mode is introduced into data delete operation, so that times for repeatedly reading and writing the data in a certain cluster are reduced, the resource occupancy rate of the processor in an event is greatly reduced, data storage and deletion speed is improved by over 400 percent; the method is independent of an operating system, and the data is easy to transplant; and the capability of the system of acquiring and processing the data in real time is improved.

Description

At embedded ARM processor to SD card data storage and delet method

Technical field

The present invention relates to a kind of computer data storage means, relate in particular to a kind of at embedded-type ARM (Advanced RISC Machines) processor to SD card data storage and delet method.

Background technology

Along with development of Embedded technique, especially aspect Industry Control, embedded system is strong with specificity, cost is low, performance is high, good stability and more and more widely being used.Based on the microprocessor of ARM kernel,, saving energy low with performance height, cost, abundant external expanded circuit, exploitation is convenient is being used widely aspect the embedded industry control.

The data acquisition storage is preserved the data of a large amount of embedded systems collection in real time and the data that system uses as a pith of built-in field.The SD card is used widely with its high capacity, high-performance, and it is integrated solid dielectric simultaneously, without any movable part, does not worry the damage of mechanical motion, becomes the first-selection of embedded memory device.In order effectively to visit the data of SD card storage, generally in the SD card, introduce embedded file system simultaneously.

Existing embedded real-time data acquisition system, general embedded ARM processor management data collection and the store tasks that adopts no operating system, when the SD card is operated, especially the real-time data acquisition class is used, can occur because excessive frequent small amount of data writes and the data deletion demand, make processor waste ample resources be used to handle the low speed peripheral hardware time, between collection and store tasks, switch repeatedly, cause real-time to be subjected to very big influence.

Being extensive use of of Windows operating system makes the FAT file system become first-selection.Because the FAT32 file system is subjected to rolling up the restriction of size and the restriction of file directory maximum number unlike FAT12, FAT16, is particularly suitable as embedded file system.At industrial control field, efficiently data storage, read, delete and can reduce the loss of peripheral hardware cpu resource, make the performance that improves embedded system in and the application that data storage is frequent less to greatest extent, especially in application facet such as real-time data acquisition, data processing in the single operation data volume.

Summary of the invention

The objective of the invention is to, provide a kind of at need not embedded ARM processor that operating system supports to SD card data storage and delet method, this method can increase substantially that its data write and deletion speed, be reduced in data acquisition use in SD card data storage operations to the occupation rate of system resource.

In order to realize above-mentioned task, the present invention takes following technical solution to be achieved:

A kind of at embedded ARM processor to SD card data storage and delet method, it is characterized in that, this method writes SD card by buffer memory and timer in the mode of fixed size or set time with randomness and sudden strong data manipulation, specifically carries out according to the following steps:

1) arm processor sticks into the foundation of capable initialization and FAT32 file to SD;

2) in internal memory, set up the data buffer area of one 512 byte;

3) clock timer is set, makes clock timer count 500ms and produce interruption;

4) the SD card data operation request based on arm processor is judged:

A is if data write request is then carried out following operation:

(1) as data volume less than buffer size, then deposit buffer area in and start timer;

(2) if before timer interrupts taking place, there is not data write operation for the second time, the data in the buffer area are write in the SD card;

(3), continue to deposit data in buffer area if before timer interrupts, still have data to write request;

(4) if data volume more than or equal to buffer size, then in time writes in the SD card;

B is if following operation is then carried out in the data deletion request:

(1) only take a document cluster when file, this document bunch is the 2KB byte, reads corresponding bunch number and writes 0XFF, 0XFF, 0XFF, 0X0F;

(2) take two document clusters or greater than two document clusters when file, each document cluster is the 2KB byte, judge that whether this bunch number be in the same data block with last one bunch number, continue to handle this bunch number if be in the same data block, if this bunch number and last not being in for one bunch number with in the cluster number, amended document cluster number is write the SD card, and from newly reading another blocks of data, bunch whole set of number quilt that take until file.

The present invention preserves and the deletion required time significantly reducing data in and the single data volume smaller applications higher in embedded data acquisition field frequency, reduces data preservation and the deletion demand to processor resource.

Method of the present invention has been introduced judgment mode in the data deletion operation, reduced the number of times of read-write repeatedly to data in certain cluster, realized not relying on embedded ARM processor efficiently the writing and deletion action of operating system to the SD card, thereby reduced the resources occupation rate of processor in this type of incident significantly, data are preserved and deletion speed has improved more than 400%, increase substantially data access speed, and do not rely on operating system, transplant simple.

Description of drawings

Fig. 1 is a file write operation process flow diagram;

Fig. 2 is the file delete operational flowchart.

The present invention is further detailed explanation below in conjunction with accompanying drawing.

Embodiment

Acquiescence entered the SD communication pattern after the SD card powered on, at this moment to stick into capable initialization to SD, initialization procedure is mainly finished the obtaining of information such as size of capacity, the card of setting, the card of SD card frequency of operation, the most important thing is the setting of SD card data block length, at the general setting of built-in field one block size is 512 bytes, and this is consistent with the allocation units size that Windows operating system is given tacit consent to also.This process is finished by writing the SD card command to the SD card.

The English full name of FAT is File Allocation Table, means file allocation table, and bunch number 32 bits of use of 32 each document cluster of expression come addressing.Bunch be the least unit of file access, file system by bunch dividing and manage, bunch is the base unit of allocation of space and recovery to the storage space of data field.Be generally 2 times, 4 times, 8 times, 16 times of block size (promptly 2 ⁿDoubly).From statistics, the average space of 0.5 bunch of each file wastes both, bunch big more, the waste of storage file time space is many more, utilization factor is low more, therefore built-in field a document cluster should be provided with excessive, be generally 4 times or 8 times of block size.

The FAT32 file system is three parts with the spatial division of Logical Disk, is boot section (BOOT district), file allocation list area (FAT district), data field (DATA district) successively.

The information such as entry address in the parameter that boot section (BOOT district) log file system is the most basic and FAT1, FAT2 table and DATA district.FAT1 and FAT2 are writing down duplicate document cluster chain index structure, because these district's data are extremely important, therefore use FAT2 as backup.Root directory area writes down filename, file attribute, the establishment visit of each file and revises date and position and file size in the FAT table.Creating a file and will operate this district and revise corresponding TAT concordance list simultaneously, also is will revise this district equally to delete index record in the TAT table simultaneously and delete a file.

For the efficient that improves CPU, reduce the loss of peripheral hardware to cpu resource, reduce the number of times that CPU reads SD card data block to greatest extent.This is to improving system real time performance significant role.

When file is carried out write operation, according to this document in the FAT district, write down bunch number, calculate the address that file data is stored in the data field, under the general situation, file data is very little when writing, information such as tens bits, if at this moment trigger write operation one time, this can cause cpu resource to expend in a large number in peripheral hardware operation at a slow speed, here, need to introduce the buffer area of a blocks of files size and clock timer is set, the value of timer is according to the data acquisition rate of data system and definite, the time interval of general timer is set to 500ms, and timer is counted 500ms and promptly produced interruption.

Writing fashionablely when file, is in time to write the data field or leave buffer area in according to the size decision file that writes file, simultaneously the timer value of She Dinging and start timer.If the second time, data did not write before timer interrupted taking place, in time the data with buffer zone deposit in, if still have request of data to write before timer interrupts, these data are continued to deposit in buffer area.

Its write operation flow process is as shown in Figure 1: the size of judgment data piece at first, if data block is less than 512 bytes, deposit data buffer area in, and startup timer, judge then whether timer arrives the time of setting (500ms), if before timer interrupts, still have data to write request, continue to deposit data in buffer area; If do not have then in time deposit the data of data buffer area in the SD card, on the contrary, when timer does not also reach the timing value of 500ms, when memory data output has reached the data buffer area size, should in time deposit data in the SD card, prevent that data from overflowing.

When file is carried out deletion action, the lot of data operation will occur in removes FAT bunch number that this document takies, when file relatively hour, as long as read corresponding bunch number and write 0XFF, 0XFF, 0XFF, 0X0F, but when file is big, reading of need not stopping revised and to be write document cluster number, can waste a large amount of system resource.Whether the number of times that reduces read-write piece number can be in the same data block with last one bunch number by judging this bunch number, continue to handle bunch number if be in the same data block, if be not in in the cluster number, amended document cluster number is write the SD card, and from newly reading another blocks of data, bunch whole set of number quilt that take until file.Can infer that file is big more, the efficient of this deleted file method is just high more.

Its deletion action flow process is as shown in Figure 2: at first file is used the number of clusters amount to subtract 1, if the result is 0, continue to judge the operation of having read FAT, if the result is not 0, read a bunch number access site data block and be revised as 0X00, read down cluster number, judge then to be in the same data block for new bunch number, if return; If not, data block is write a bunch number place FAT1, FAT2 position, read the storaging position data piece new bunch number, return.If, then being revised as 0X00, data block writes a bunch number place FAT1, FAT2 position then, and file delete successfully returns.If not, read a bunch number access site data block, be revised as 0X00 then.

Claims

One kind at embedded ARM processor to SD card data storage and delet method, it is characterized in that, this method writes SD card by buffer memory and timer in the mode of fixed size or set time with randomness and sudden strong data manipulation, specifically carries out according to the following steps:

1) arm processor sticks into the foundation of capable initialization and FAT32 file to SD;

2) in internal memory, set up the data buffer area of one 512 byte;

3) clock timer is set, makes clock timer count 500ms and produce interruption;

4) the SD card data operation request based on arm processor is judged:

A is if data write request is then carried out following operation:

(1) as data volume less than buffer size, then deposit buffer area in and start timer;

(2) if before timer interrupts taking place, there is not data write operation for the second time, the data in the buffer area are write in the SD card;

(3), continue to deposit data in buffer area if before timer interrupts, still have data to write request;

(4) if data volume more than or equal to buffer size, then in time writes in the SD card;

B is if following operation is then carried out in the data deletion request:

(1) only take a document cluster when file, this document bunch is the 2KB byte, reads corresponding bunch number and writes 0XFF, 0XFF, 0XFF, 0X0F;

(2) take two document clusters or greater than two document clusters when file, each document cluster is the 2KB byte, judge that whether this bunch number be in the same data block with last one bunch number, continue to handle this bunch number if be in the same data block, if this bunch number and last not being in for one bunch number with in the cluster number, amended document cluster number is write the SD card, and from newly reading another blocks of data, bunch whole set of number quilt that take until file.