FAT16/32 format to write MMC with PIC18F4520 Problem

[malimutlu]

Hello,

I am trying to write 4 channel analog data to MMC with PIC18F4520. Everything is fine for collecting data from A/D channels and write all 512bytes to buffer, however when buffer is reach 512 byte then spi is trying to write MMC with FAT format but it takes too much time (is about 60ms) for my 10ms interrupt routine. (because i could not collect 6 set of datas, they are all lost).

Could anybody suggest me how can i reduce MMC writing time problem with my microcontroller?

Possible Suggestions:
1. Another file format? (i try both fat16 and fat32)
2. Another type of microcontroller, which is faster then PIC18F4520
etc.

thanks for your attention.

[FvM]

You get a considerable overhead by updating FAT and directory data. Because a PIC18 hasn't sufficient memory to buffer these structures, read-modify-write has to be performed each time. Using a faster processsor with more RAM can speed up these operations. Alternatively, you can write the data to a predefined file area without accessing FAT data at all.

[asmallri]

[FvM]

I was under the assumption, that you have difficulties to achieve the required overall sustained write speed, but re-reading your post, I completely agree with Andrew that suitable buffering should do the trick. For your data rate, a PIC18 should work.

I also can confirm the good quality of the brushelectronics drivers.