March 14th, 2013, 04:53 AM
Help with choosing PIC
We are currently working on a project using GSM and RFID to lock and unlock a safe. Currently we are working with PIC18F4520 with C18. Now we want to implement a SD card function onto it. After much work, it seems that the SD card needs 55k of memory to make it work... Since the 4520 is just 32k of memory, we are considering changing PIC to make this work...
So we are planing to change to a 64k bit memory pic like the PIC18F4610...
We've done much research on the datasheets, but still we just wanted to make sure if all our requirements are available on this new PIC.
We use USART, both hardware and a software usart, and interrupts...
March 14th, 2013, 06:13 AM
You can get an SD card to work in far less memory than that! How did you determine that figure? What file system library are you using? Consider ELM's FatFs or even smaller Petit FAT library.
The memory usage for these on a variety of architectures is shown here and here respectively.
Given that your memory requirement estimate seems unlikly, you probably need not change your target at all, and even if you did it seems a simple case of getting the one with the necessary performance, peripherals and memory resources. Either way, I would avoid using PIC for pretty much anything, often you will find more powerful Cortex-M parts from a number of vendors for similar cost, and they are much nicer to work with. I have implemented a bootloader on Cortex-M3 that supports firmware update over SD, USB and UART and the whole thing comes in at less than 16K of ROM and 8K or RAM, and the USB support is responsible for most of that.
Last edited by clifford; March 14th, 2013 at 06:16 AM.
March 14th, 2013, 11:31 AM
Do you have any working examples on these file systems? And what library could I use for these?
Currently I'm using the Microchips MDD File System Library. There are many working examples on this. And given that I have to achieve this result within few days, I find the option of changing the microcontroller the easiest at this moment, unless I find a working example on this aswell and that would make it so much more easier for me.
March 14th, 2013, 04:26 PM
Wow, I took a look at the MDD app note and the memory usage is truely terrible, especially given the size of most PIC parts.
Originally Posted by samans
Regarding examples this may help, but all I did to find that was to Google it!