PmodSD Reference Manual
The Digilent PmodSD (Revision B) allows system boards to read from and write to SD cards. With no limitation on the file system or memory size of the SD card, users will be able to store and access large amounts of data from their system board.
- Full size SD card slot
- Store and access large amounts of date from your system board
- No limitation on file system or memory size of SD card used
- 1-bit and 4-bit communication
- Small PCB size for flexible designs 1.8“ × 1.8” (4.6 cm × 4.6 cm)
- 12-pin Pmod port with SPI interface
The PmodSD is a great way to store and access information on a device that can then be accessed by outside devices such as a phone or computer.
Interfacing with the Pmod
The PmodSD is designed to communicate with the host board primarily through the SPI protocol. By default, the SD card itself is defined to boot up in SD mode, but will enter into SPI mode when the Chip Select line is pulled low. The actual technique of writing to and reading from specific locations on an SD goes beyond the scope of this document, but the complexity of the process is nicely abstracted away within the chipKIT SD library. More details about how the SD library works can be found in our PmodSD user guide (once I create the user guide anyway; I am finishing all of the reference manuals first).
A pinout description table and diagram for the 2×6 pin header on the PmodSD can be found below:
|Connector J1- Pin Descriptions|
|1||~CS||Chip Select / Data3||7||DAT1||Data 1|
|2||MOSI||MOSI / Command||8||DAT2||Data 2|
|3||MISO||MISO / Data0||9||CD||Card Detect|
|4||SCK||Serial Clock||10||WP||Write Protect|
|5||GND||Power Supply Ground||11||GND||Power Supply Ground|
|6||VCC||Power Supply (3.3V)||12||VCC||Power Supply (3.3V)|
Any external power applied to the PmodSD must be within the specifications of the inserted SD card. As determined by the SD card association, this voltage range must be within 2.7 to 3.6 volts. The 3.3 operating voltage on Digilent system boards nicely complies with this standard.
The pins on the pin header are spaced 100 mil apart. The PCB is 1.8 inches long on the sides parallel to the pins on the pin header and 1.8 inches long on the sides perpendicular to the pin header.
The schematics of the PmodSD are available here. Additional information about the standard SD protocol can be found from the SD Card Association here in the Physical Layer Simplified Specification (Version 4.0)
If you have any questions or comments about the PmodSD, feel free to post them under the appropriate section (“Add-on Boards”) of the Digilent Forum.