SD Card Questions
Hello,
I was planning my designs and I was wondering how I could minimize the number of pins I would have to sacrifice in order to interface the propeller to an SD card. I understand that there is the Card Select, which cannot be omitted. As for the Clock (SCLK), can I just use an external oscillator?
The Data Output is needed because I want to pull data from the card, but can the Data Input be pulled to a rail if I do not intend to write anything to do the card, or is it necessary to communicate with this pin to have the SD card do stuff?
Thank you so much,
Sean
I was planning my designs and I was wondering how I could minimize the number of pins I would have to sacrifice in order to interface the propeller to an SD card. I understand that there is the Card Select, which cannot be omitted. As for the Clock (SCLK), can I just use an external oscillator?
The Data Output is needed because I want to pull data from the card, but can the Data Input be pulled to a rail if I do not intend to write anything to do the card, or is it necessary to communicate with this pin to have the SD card do stuff?
Thank you so much,
Sean
Comments
Is there anything wrong with using an external oscillator for the SD card's clock?
The clock (CLK) is how the SD card is synchronized with the microcontroller. An external oscillator would not work.
http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus
Rich H
Thanks.
Bill
I realized that 30 and 31 were available but I am a little concerned with doing things while the EEPROM is connected. Is there a chance it could accidentally be triggered to do something?
Use some kind of I/O expander. They're cheap and easy to use. The I2C ones can even be connected to the same I/O pins (28 and 29) as the EEPROM. You could easily use up to 8 PCA9554 I/O expanders for 8 I/O pins each, all on pins 28 and 29.
This should work on most spi devices, but I am not aware of the SD protocol.