In this article we will examine another product from a bundle sent for review by Snootlab, a Toulouse, France-based company that in their own words:
… designs and develops electronic products with an Open Hardware and Open Source approach. We are particularly specialized in the design of new shields for Arduino. The products we create are licensed under CC BY-SA v3.0 (as shown in documents associated with each of our creations). In accordance with the principles of the definition of Open Source Hardware (OSHW), we have signed it the 10th February 2011. We wish to contribute to the development of the ecosystem of “do it yourself” through original designs of products, uses and events.
Furthermore, all of their products are RoHS compliant and as part of the Open Hardware commitment, all the design files are available from the Snootlab website.
The subject of the review is the Snootlab Mémoire – an SD card data logging shield with on-board DS1307 real time clock [and matching backup battery] and prototyping area. It uses the standard SdFat library to write to normal SD memory cards formatted in FAT16 or FAT32. You can download the library from here. The real time clock IC is an easy to use I2C-interface model, and I have documented its use in great detail in this tutorial.
Once again, shield assembly is simple and quite straightforward. You can download an illustrated assembly guide from here, however it is in French. But everything you need to know is laid out on the PCB silk-screen, or the last page of the instructions. The it arrives in a reusable ESD bag:
… and all the required parts are included – including an IC socket and the RTC backup battery:
… the PCB is thick, with a very detailed silk-screen. Furthermore, it arrives with the SD card and 3.3V LDO (underneath) already pre-soldered – a nice touch:
The order of soldering the components is generally a subjective decision, and in this case I started with the resistors:
… and then worked my way out, but not fitting the battery nor IC until last. Intrestingly, the instructions require the crystal to be tacked down with some solder onto the PCB. Frankly I didn’t think it would withstand the temperature, however it did and all is well:
Which leaves us with a fully-assembled Mémoire shield ready for action:
Please note that a memory card is not included with the kit. If you are following along with your own Mémoire, the first thing to do after inserting the battery, IC and shield into your Arduino board and run some tests to ensure all is well. First thing is to test the DS1307 real-time clock IC. You can use the following sketch from chapter seven of my Arduino tutorial series:
reading and writing to the Maxim DS1307 real time clock IC
based on code by Maurice Ribble
17-4-2008 - http://www.glacialwanderer.com/hobbyrobotics
#define DS1307_I2C_ADDRESS 0x68
// Convert normal decimal numbers to binary coded decimal
byte decToBcd(byte val)
return ( (val/10*16) + (val%10) );
// Convert binary coded decimal to normal decimal numbers
byte bcdToDec(byte val)
return ( (val/16*10) + (val%16) );
// 1) Sets the date and time on the ds1307
// 2) Starts the clock
// 3) Sets hour mode to 24 hour clock
// Assumes you're passing in valid numbers
void setDateDs1307(byte second, // 0-59
byte minute, // 0-59
byte hour, // 1-23
byte dayOfWeek, // 1-7
byte dayOfMonth, // 1-28/29/30/31
byte month, // 1-12
byte year) // 0-99
Wire.send(decToBcd(second)); // 0 to bit 7 starts the clock
Wire.send(00010000); // sends 0x10 (hex) 00010000 (binary) to control register - turns on square wave
// Gets the date and time from the ds1307
void getDateDs1307(byte *second,
// Reset the register pointer
// A few of these need masks because certain bits are control bits
*second = bcdToDec(Wire.receive() & 0x7f);
*minute = bcdToDec(Wire.receive());
*hour = bcdToDec(Wire.receive() & 0x3f); // Need to change this if 12 hour am/pm
*dayOfWeek = bcdToDec(Wire.receive());
*dayOfMonth = bcdToDec(Wire.receive());
*month = bcdToDec(Wire.receive());
*year = bcdToDec(Wire.receive());
byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
// Change these values to what you want to set your clock to.
// You probably only want to set your clock once and then remove
// the setDateDs1307 call.
second = 0;
minute = 33;
hour = 22;
dayOfWeek = 2;
dayOfMonth = 4;
month = 07;
year = 11;
setDateDs1307(second, minute, hour, dayOfWeek, dayOfMonth, month, year);
byte second, minute, hour, dayOfWeek, dayOfMonth, month, year;
getDateDs1307(&second, &minute, &hour, &dayOfWeek, &dayOfMonth, &month, &year);
Serial.print(hour, DEC);// convert the byte variable to a decimal number when being displayed
Serial.print(" Day of week:");
// Serial.println(dayOfWeek, DEC);
If you are unsure about using I2C, please review my tutorial which can be found here. Don’t forget to update the time and date data in void setup(), and also comment out the setDateDS1307() function and upload the sketch a second time. The sketch output will be found on the serial monitor box – such as:
Those of you familiar with the DS1307 RTC IC know that it can generate a nice 1 Hz pulse. To take advantage of this the SQW pin has an access hole on the PCB, beetween R10 and pin 8 of the IC:
For instruction on how to activate the SQW output, please visit the last section of this tutorial.
The next test is the SD card section of the shield. If you have not already done so, download and install the SdFat libary. Then, in the Arduino IDE, select File > Examples > SdFat > SdFatInfo. Insert the formatted (FAT16/32) SD card into the shield, upload the sketch, then open the serial monitor. You should be presented with something like this:
As you can see the sketch has returned various data about the SD card. Finally, let’s log some data. You can deconstruct the excellent example that comes with the SdFat library titled SdFatAnalogLogger (select File > Examples > SdFat > SdFatAnalogLogger). Using the functions:
you can “write” to the SD card in the same way as you would the serial output (that is, the serial monitor).
If you have reached this far without any errors – Congratulations! You’re ready to log. If not, remove the battery, SD card and IC from your shield (you used the IC socket, didn’t you?). Check the polarised components are in correctly, double-check your soldering and then reinsert the IC, shield and battery and try again. If that fails, support is available on the Snootlab website, and there is also a customer forum in French (use Google Translate). However as noted previously the team at Snootlab converse in excellent English and have been easy to contact via email if you have any questions. Stay tuned for the final Snootlab product review.
As always, thank you for reading and I look forward to your comments and so on. Furthermore, don’t be shy in pointing out errors or places that could use improvement. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts, follow on twitter, facebook, or join our Google Group.
[Disclaimer – the products reviewed in this article are promotional considerations made available by Snootlab]