SD卡和图片有底端吗？

我使用了一个18F45 J50与MLA USB堆栈+MDD。我似乎记得它有点紧内存，但OK（我想我不得不离开FSFPrftff（），但没有太多其他）。



      以下为原文

    I used an 18F45J50 with the MLA USB stack + MDD.
I seem to recall it being a bit tight on memory, but OK (I think I had to leave out FSfprintf(), but not much else).

不，SD卡不是USB。所以我需要一个文件系统。它需要什么大小的缓冲区512字节或完整的集群。



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    No, SD Cards not USB.
So I need a file system. what size buffer does it need 512 bytes or a full cluster.

旧的MLA文件系统的内存使用详见AN1045。http://www. McCyp.com….ASPX？AppNeNo.En5340



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    The memory usage of the old MLA filesystem is detailed in AN1045.
http://www.microchip.com/....aspx?appnote=en532040
 

我有一个PIC24的原因有几个，但是PIC18确实可以处理它们，只要有3-4KB的RAM在那里。



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    I'd go with a PIC24 for several reasons, but indeed a PIC18 can handle them, provided some 3-4KB RAM are there

您好，我建议Elm Chan FatFs文件系统图书馆。HTTP://ELMCHAN.OF/FSW/FF/00索引x.HMLYU可能需要提供一些SDI硬件接口功能。我的PIC18F26K22的原型项目是附加的，它确实是建立的，但没有被测试。K22、K40或K42都应该能够做到这一点，F25设备。如果程序中还需要其他代码，则32字节的程序内存可能变得紧张，但是有可能修整文件系统的配置，而ELM Chann网站也有小型微控制器的实现。PIC18F25K42具有不同的SPI模块。Pic18F26K42和PIC18F27 K42仍然在未来，从我在Microchip网站上可以看到的。问候，Mysil



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    Hi,
I'd suggest Elm Chan FatFs filesystem library.
http://elm-chan.org/fsw/ff/00index_e.html
You may need to provide some SDI hardware interface functions.
 
My prototype project for PIC18F26K22 is attached, it does build, but isn't tested at all.
K22, K40 or K42 should all be able to do this, F25 devices with 32kByte program memory may become tight if there is also other code needed in the program, but there are possibilities to trim the configuration of the filesystem, and the Elm ChaN website also have implementations for smaller microcontrollers.
 
PIC18F25K42 have a different SPI module from the predecessors.
PIC18F26K42 and PIC18F27K42 are still in the future, from what I can see in Microchip website.
 
Regards,
   Mysil
   Attachment(s)

SD_Card.zip (72.61 KB) - downloaded 358 times

谢谢大家。



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    Thanks all.

我使用ELM Chan-FATFS文件系统库。它在PIC32项目上，但它用于引导加载程序，所以大小是很重要的。该库是可配置的大小与功能。在PIC32上，只读大约10K，读写12K，其他特征是目录和长文件名，两者都占用更多内存，不确定有多少。



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    I use Elm Chan FatFs filesystem library.  Its on a PIC32 project, but its used for the bootloader, so size is important.   The library is configurable for size vs features.  On a PIC32 it takes about 10K for read only, 12K for read/write, the other features are directories and long filenames, both take more memory, not sure how much.

SD卡通常一次读取512字节（扇区读取）。取决于所需的功能（读、写、目录等），程序的大小会有很大的变化。我有一个16F1829从SD卡读取文件，剩余的ROM空间很多，但是在可用的功能中非常受限。这决定了PIC的使用：您需要哪些文件系统功能以及执行这些文件需要多快。



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SD cards are normally read 512 bytes at a time (sector reads). Depending on the functions needed (read,write, directory, etc) the size of the program will vary greatly. I have a 16F1829 that reads files from an SD card with lots of ROM space left over but it is very restricted in the available functions. That is what determines the pic to use: which file system functions you need and how FAST do you need to perform them.

简单地说，如果你只阅读，你可以通过最小的RAM，但如果你需要写，那么你需要一个部门缓冲区在本地RAM。



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    Plainly if you're only reading, you can get by on minimal RAM, but if you need to write at all, then you will need a sector buffer in local RAM.
 

我可以在PIC18上确认FATFS读写良好，使用~20KB Flash和2LB RAM。你不需要特别壮观的照片。



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    I can confirm FatFS read/write works fine on a PIC18, using ~20KB flash and < 2KB RAM.  You don't need an especially beefy PIC.

我假设SPI上的DMA会有帮助。这是一个可能需要的特性，但是它似乎在推动设计。



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    I assume DMA on the SPI would help.
It is a might need feature, but it seems to be driving the design.

FatFS结构严谨。接口层在文件MMC.C中，至少需要为SPI和计时器提供硬件接口。如果需要速度，也可以用DMA替换DISKYRADE和DISKYX写函数。



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    FatFS is well structured.  The interface layer is in the file mmc.c.  At a minimum you need to provide the hardware interface for the SPI and the timer.  You can also replace the disk_read and disk_write functions with a DMA if you need the speed.