Electronic circuit design diagram of SD card file system implemented by ARM9 core μC/OS-II system

Based on the ARM9 embedded processor and μC/OS-II operating system, the SD card, a storage medium with large capacity, small size and high cost performance, is used to store long-term measurement data. The FAT32 is cropped and combined with the SD card. The underlying reading and writing program realizes the embedded SD card file system, which makes it easy to query, comprehensively analyze and back up the truck weighing data recorded on the SD card through the host computer. At the same time, this method provides a non-volatile memory solution for other data collection systems. The collected data will be recorded on the SD card in a standard file format to facilitate unified management of files. The system has the characteristics of strong real-time performance, high access rate, easy maintenance and easy transplantation.

1. Hardware circuit

The hardware development platform processor of this system is S3C2440A, which is a 16/32-bit RISC microprocessor launched by Samsung, ARM920T core, main frequency 400 MHz, up to 533 MHz, and has rich system peripheral controllers and various communications internally. interface. SD card supports two communication modes: SPI and SD. S3C2440A has an SD card interface and supports SD bus mode, so it no longer uses SPI mode like low-end ARM processors, but uses SD bus mode, which can greatly improve the performance of SD cards. reading and writing speed. The interface circuit between S3C2440A and SD card reader/writer is shown in Figure 1.

Figure 1 SD card interface circuit

The DAT0~DAT3, CLK (clock line) and CMD (command line) of the SD card are connected to the SDDATA0~SDDATA3, SDCLK ​​and SDCMD pins of the S3C2440A respectively. The SD card supports single-line and wide bus data transmission. The wide bus data is transmitted 4 bits at a time, which is several times faster. Therefore, this design adopts the wide bus method.