The datalogger shield has a few things to make it an excellent way to track data. Here's a rough map of th shield:
Our latest version adds power rails for 5V, 3.3V and Ground:
The big SD card holder can fit any SD/MMC storage up to 32G and and small as 32MB (Anything formatted FAT16 or FAT32) If you have a MicroSD card, there are low cost adapters which will let you fit these in. SD cards are tougher to lose than MicroSD, and there's plenty of space for a full size holder.
Simply Push to insert, or Pull to remove the card from this slot
The SD Activity LED is connected to the clock pin, it will blink when data goes over SPI, which can help you detect when its ok to remove or insert the SD card or power down the Arduino.
The Level Shifter moves all signals from 3.3 or 5V down to 3.3V so you can use this shield with any Arduino safely and not damage cards. Cheaper shields use resistors to level shift, but this doesn't work well at high speed or at all voltage levels!
This is the time-keeping device. It includes the 8-pin chip, the rectangular 32KHz crystal and a battery holder
The battery holder must contain a battery in order for the RTC to keep track of time when power is removed from the Arduino! Use any CR1220 compatible coin cell
An on-board 3.3V LDO (low drop-out type) regulator keeps the shield's 3V parts running smoothly. Some old Arduinos did not have a full 3.3V regulator and writing to an SD card could cause the Arduino to reboot. To maintain compatibility we just keep it there. There's also a green PWR (Power) good LED to the right
We have two user-configuratble LEDs. Connect a wire from any Arduino pin to L1 or L2 marked pads and pull high to turn on LED1 or LED2
The reset button to the right of the LEDs, will reset the entire Arduino, handy for when you want to restart the board
The big middle section is filled with 0.1" grid prototyping holes so you can customize your shield with sensors or other circuitry.
The top two and bottom two rows of proto holes are power rails.
We also have some extra breakouts shown above, around the breakout board area.
To the right of the SD card holder:
- CD - this is the card detect pad on the SD card. When this is connected to ground, an SD card is inserted. It is open-drain, use a pullup (either physical resistor or enabled in software)
- WP - this is the Write Protect pad on the SD card, you can use this to detect if the write-protect tab is on the card by checking this pin. It is open-drain, use a pullup (either physical resistor or enabled in software)
- SQ - this is the optional Squarewave output from the RTC. You have to send the command to turn this on but its a way of optionally getting a precision squarewave. We use it primarily for testing. The output is open drain so a pullup (either physical resistor or enabled in software)
- 3V - this is the 3V out of the regulator. Its a good quality 3.3V reference which you may want to power sensors. Up to 50mA is available
Near Digital #10
- CS - this is the Chip Select pin for the SD card. If you need to cut the trace to pin 10 because it is conflicting, this pad can be soldered to any digital pin and the software re-uploaded
Near Digital #3 and #4
- L2 and L1 - these are optional user-LEDs. Connect to any digital pin, pull high to turn on the corresponding LED. The LEDs already have 470 ohm resistors in series.