MicroSD / Transflash SPI Initialization

[bishopd]

microsd spi

I am interfacing a MCU to a microSD / transflash card using the SPI bus, but ran into some problems. I start by sending 160 clock with the chip select de-asserted (high) and the asserted the chip select and send CMD0 and correctly got the reponse 0x01. I then followed up by sending a CMD1 to take the card out of idle mode, but the idle bit is still set when I get the reponse 0x01. I then send another CMD1 to try to get the idle bit set to 0, and card stops talking. I have also tried send CMD55 and the ACMD41, but it does the same. I noticed the current draw is raised from ~1mA to ~20mA when I send the CMD1. Sending any command will again drop the current to ~1mA. Any ideas on what I am doing wrong????

 

[mgf]

microsd initialization

Hello bishopd,

After CMD1 send a dummy byte out , say $FF, then check if the card is out of idle in the next spi bus interrogation.

Use somenting like this:

Repeat
Low SD_PIN_CS ; select card
CMD1
SPI $FF ; send a dummy byte on spi bus
SPI $FF ; send again and
Until Inbyte = 0 ; you NOW check for $00
SPI $FF ; dummy byte again
High SD_PIN_CS ; release card

That should work.
HTH

Best regards,
mgf