ETT boards : Mini SD
So you need a gigabyte of storage for your microcontroller project. If I would have said something similar in
the 80's, they would have sent an ambulance with two nurses and a straightjacket. After a mild sedation I
would have woken up in nice big house in a woody area, occupied by other loonies. Never to come out again.
But this isn't the 1980's. This is 2008. Now people need to gather (and KEEP) lots of data. So a GB of data
storage for a micro controller isn't far fetched. And it's also quite easy to implement: just add a small SD
card to your project.
SD cards are cheap. So it's a challenge to interface them. And here comes the funny part: the SD card can be
controlled via SPI. And most serious microcontrollers of the time have SPI built in. On silicon. So just a
small interface board would do. And that's just what this board is about.
Some features:
ET Mini SD : manual
This card is to interface SD or MMC cards with your microcontroller project. Just connect it using the 10 pin SIL connector. This small card has many interesting features, such as Card Detect signal and LED and Pull up circuitry for Card Detect line.
ET Mini SD : with 5 Volt supply
When you need to use the Mini SD board with a microconbtroller running on 5 Volts, you need a level converter. ETT make a special board for this, the 'Logic Converter Mini Board'. It must be powered with 5 Volts and the onboard LDO will convert it to 3.3 Volts, with which you can then run the 'Mini SD' board. Take a look at the circuit drawing below:
ET Mini SD : Signal lines for SD cards
There are two methods to control the SD card:
| SD mode | SPI mode | ||||||
|---|---|---|---|---|---|---|---|
| Pin | Name | Type | Description | Name | Type | Description | |
| 1 | CD/Data3 | I/O PP | Card Detect or Data3 | CS | I | Chip Select (Active low) | |
| 2 | CMD | I/O PP | Command/Response | DataIn | I | Host to card commands and data | |
| 3 | Vss | S | Ground | Vss | S | Ground | |
| 4 | Vdd | S | 3.3 Volt | Vdd | S | 3.3 Volt | |
| 5 | CLK | I | Clock | CLK | I | Clock | |
| 6 | Vss | S | Ground | Vss | S | Ground | |
| 7 | Data2 | I/O PP | Data2 | DataOut | O | Card to host data | |
| 8 | Data1 | I/O PP | Data1 | Res | - | Reserved | |
| 9 | Data0 | I/O PP | Data0 | ||||
ET Mini SD : Signal lines for MMC cards
The MMC cards also have two modes of operation:
| MMC mode | SPI mode | ||||||
|---|---|---|---|---|---|---|---|
| Pin | Name | Type | Description | Name | Type | Description | |
| 1 | N/C | - | Not used, always "1" | CS | I | Chip Select (Active low) | |
| 2 | CMD | I/O PP OC | Command/Response | DataIn | I | Host to card data | |
| 3 | Vss | S | Ground | Vss | S | Ground | |
| 4 | Vdd | S | 3.3 Volt | Vdd | S | 3.3 Volt | |
| 5 | CLK | I | Clock | CLK | I | Clock | |
| 6 | Vss | S | Ground | Vss | S | Ground | |
| 7 | Data2 | I/O PP | Data2 | DataOut | O | Card to host data | |
Read more about SD cards here: http://en.wikipedia.org/wiki/Secure_Digital_card .
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