Jim, OK, back in the forum now.
There is a project here that i copied, so that i could learn more about avr's. Its the simplest mp3 player i could find as a project. Anyway it uses a lirbrary FAT.h to read from the SD card, (pretty sure it is anyway...)
So that i can learn a little more i am trying to change the mp3 player so that it now can give out warnings or messages based on sensor inputs.
I have succesfully got it to respond by playing mp3's based on sensor inputs such as it says too hot, when a thermometer readches over 30 degrees C.
This was pretty simple to be honest, I studied the code to work out how it decided what mp3 to play (its done on the index number of the actual mp3 file on the sd card), and modifed the code to play certain mp3's at certain times...
Now though I want to be able to store a number in a text file on the SD card, so that i can be called back if the machine was ever turned off.
So I can read from the card, but I am not sure how to write to the SD card.
In windows I know it is fopen, fprintf, and fclose,
but windows takes care of alot. How do i do the equivelent with the SD card, if all the libraries for FAT are there and FAT_Init() has been initiased.
To be honest i am not sure (and wouldnt bank on it) that it is FATfs, because the library is called FAT.h