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Interfacing SD / MMC Card with SPI
Library to easily interface SD cards using the uFAT technique can be found here if you are interested in the development of it or want to request features, go to here.
As for 20090217 allows to easily read/write/append/delete contents from/to files.
Filesystem
SD-Card must be formatted with FAT-16 Filesystem with only a single partition on it.
SD / MMC Pinout
SD
Pinout
| SD Mode | SPI Mode | |||||
|---|---|---|---|---|---|---|
| Pin | Name | Type | Description | Name | Type | Description |
| 1 | CD/DAT3 | I,O | Card detection / Data Line 3 (Bit 3) | CS | I | Chip Select (Active low) |
| 2 | CMD | I,O | Command/Response | DataIn | I | Host to Card Commands and Data |
| 3 | VSS1 | S | Supply Voltage Ground | VSS1 | S | Supply Voltage Ground |
| 4 | VDD | S | Supply Voltage | VDD | S | Supply Voltage |
| 5 | CLK | I | Clock | CLK | I | Clock |
| 6 | VSS2 | S | Supply Voltage Ground | VSS2 | S | Supply Voltage Ground |
| 7 | DAT0 | I,O | Data Line 0 (Bit 0) | DataOut | O | Card to Host Data and Status |
| 8 | DAT1 | I,O | Data Line 1 (Bit 1) | RSV | - | Reserved |
| 9 | DAT2 | I,O | Data Line 2 (Bit 2) | RSV | - | Reserved |
Type: S=power supply; I=input; O=output using push-pull drivers.
MMC
Pinout
| MultiMediaCard Mode | SPI Mode | |||||
|---|---|---|---|---|---|---|
| Pin | Name | Type | Description | Name | Type | Description |
| 1 | RSV | NC | Not connected or Always "1" | CS | I | Chip Select (Active low) |
| 2 | CMD | I,O,PP,OD | Command/Response | DataIn | I | Host-to-card Command and Data |
| 3 | VSS1 | S | Supply Voltage Ground | VSS1 | S | Supply Voltage Ground |
| 4 | VDD | S | Supply Voltage | VDD | S | Supply Voltage |
| 5 | CLK | I | Clock | CLK | I | Clock |
| 6 | VSS2 | S | Supply Voltage Ground | VSS2 | S | Supply Voltage Ground |
| 7 | DAT0 | I,O,PP | Data0 | DataOut | O | Card-to-host Data and Status |
Type: S=power supply; I=input; O=output; PP: push-pull; OD: open-drain; NC: No connection or VIH.
Existing Shields
There are several shields for Arduino that handle the use of SD cards. Here some references on where to find them:
- the LadyAda wave shield
- the LadyAda GPS logger
- the official Arduino ethernet shield
- the microSD module from Libelium.com that can be purchased here
(c) 2008 picture courtesy of Libelium
(more to come...)
Author: illustrations and tables pixel::doc, SDuFAT library BlushingBoy