Hi, I use a MicroSD breakout board from Cool Component with my MBED. {{/media/uploads/okaydjo2/transflash_breakout_board.jpg}} I make the wiring between the MicroSD Breakout Board and the MBED RSV : unconnected CS\ : P8 DI : P5 (MOSI) VDD : P40 (VOUT = 3.3V) CLK : P7 (SLK) VSS : P0 (GND) DO : P6 (MISO) RSV : unconnected S1 and S2 unconnected I use the programm SDFileSystem_Hello_World-main.cpp with the SDFileSystem Library (SPI mode for the Micro SDcard). ************************************************************ include "mbed.h" include "SDFileSystem.h" SDFileSystem sd(p5, p6, p7, p8, "sd"); // Broche en fonction de la maquette de test int main() { printf("Hello World!\n"); mkdir("/sd/votredir", 0777); // Creation du repertoire votredir FILE *fp = fopen("/sd/votredir/fichier.txt", "w"); // Creation d'un fichier texte nomme fichier if(fp == NULL) { error("Le fichier ne peut pas etre ouvert pour ecrire dedans \n"); } fprintf(fp, "Bonjour les gars !\n\r La partie programmation est difficile !\n\r on va ecrire dans la microSD de 2 Go de Marque DANE ELEC\n\r"); // fclose(fp); // printf("Goodbye World!\n"); } *************************************************************** My microSD card is Dane Elec with capacity : 2 Go My problem : I can't write a file in the MicroSD card with this Breakout Board. So, I try this programm with the same MicroSD card associated with a workshop breakout board (Cool Component) and it's ok for writing the file ! {{/media/uploads/okaydjo2/workshop_dev_board.jpeg}} Someone can help me for the MicroSD breakout board ? Thanks

Try decoupling capacitors soldered NEAR the sd card, between VCC ( +3.3V) and ground. If you follow the experience of http://www.roland-riegel.de/sd-reader/index.html , solder 50microF and 100nF Look at the schema. Robert