Let's Make Robots!

External Memory Reader

Oi all,

I was finally going to get my RFID chips (I hope... maybe) and I was thinking that I wanted a way to store a database for RFID tags and actions like a database storring the ID number and if they are level 1 allowance or level 2 allaowance, etc. that way I can not only select what I can allow the person to do in a situation, but I can also easilly add people from my computer or phone (if I use Micro SD). 

Basically I want a way to read a txt file from the root of a data storage device - I'd prefer SD but Thumb drive is my next preference.

does anyone know a site with a tutorial or maybe just post  a method? I would prefer the programming be in Basic or C++ but I can hopefully take any method and try to convert it.

your friendly neighborhood RFID proponent,


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What is the hardware - I mean you have a SD or thumb drive reader - what is the other end connected to? A microcontroller? A computer?

If its a computer I know a bit about databases and such, but I don't know if that is what you want... 

There are colde libraries for PICs which do FAT. They are definitely there. I could never get them to work. Memory cards arejust a bunch of contiguous memory addresses. They're perfectly happy to be used as such. They don't need a filing system (eg FAT). Of course this means that  when you stick 'em in your PC, it has no idea what to do with it and it'll probably recommend you format it.

I attached a PIC to a CompactFlash card. Great interface. IDENTICAL to an IDE hard drive. I could never get FAT to work, so I just used it as a bunch of extended memory and read/wrote through the PIC.

THIS application note from Microchip details the use of a PIC as a USB interface to an SD card.

Here's the low level SD card interface.

This is a book, which alledgedly explains how to code for FAT in cahpter 14.

Some open source PIC based MP3 players, which have FAT and various memory card interfaces... 

By the way, it's NOT easy.

what if i need to store only a very limited amount of digits, like one single byte? what would be the best, picaxe compatible, way to do that? (considering the fact that i want to erase and re-write this memory more and more times, quickly)