looking for advice

Forum 2005-2010 (read only) Hardware Interfacing
1

I want to know if it would be a good idea to use the Arduino nano for a particular application. I need a micro controller that can do the following routine: The controller should be in sleep mode the majority of the time; it will wake up every ten minutes and take two analog voltage readings, convert these readings into digital values, perform a few mathematical calculations on the digital values and then store them in some sort of memory that can be read on a monthly basis and downloaded onto a computer. The only concern that I have with using this board for this application is that I don't know if it will have enough memory to do what I need. If I assign each data value as a type float, then it takes up 4 bytes per data value. In a one month period I will have accumulated 12,960 readings, which is 51840 bytes of data, or about 52 kB.Does anyone have any suggestions whether it would be a good idea to use Arduino nano for this application? If I need more memory than what comes with the nano, then does anyone have any good suggestions of how I could go about this?

-Thanks

2

SD/MMC card, or I2C EEPROM.

Just a thought - why do you need to do the maths when you take the sample?
Samples are at most 10 bit - still too big, but less than a third the size of a float.

3

Yea I looked at the sizes for other data types like int, which will probably work because I don't really need super high precision on the data, and they are a lot smaller (1 byte). I need to do the maths because the voltage input readings correspond to pressure values, measured in mmHg, so I have to convert using a calibration equation that I am going to develop by just seeing how the pressures change as function of voltage to the micro controller. Are there any tutorials on how to add the extra memory? I don't really know where to start. I estimated that I will need about 50 kB of storage space just for the data though.

4

Using 24LC256 eeprom chips (32KB), you can connect 2, 4, 8 of them on I2C. This solution would be cheaper (cost-wise, work-wise) than SD card.

See this article:
http://www.arduino.cc/playground/Code/I2CEEPROM

5

24LC512 (64kb) also supports writing individual bytes and is slightly less than twice the price of a 24LC256

Using 24LC256 eeprom chips (32KB), you can connect 2, 4, 8 of them on I2C.

You can connect 1-8 of them on an i2c bus, so e.g. 1 or 3 would be okay.

I'm surprised theres no mention of timestamps

6

Are there tutorials on how to add the AT24C256 (EEPROM) chip to integrate with the Arduino board?

thanks for the link by the way, I have a feeling the code will be useful if I decide to go this route.

7

Not really a guide, but the page with the code has some instructions

Because this chip is I2C, it only uses the analog pins 4 & 5 (SDA and SCL), and of course the power (5V) and GND.

Hook the eeproms SDA to analog pin 4, and its SCL to analog pin 5, also wire up some power.

Mount the chip on a breadboard?

Sometimes pullup resistors are mentioned when using i2c chips but either the atmega or the eeprom may have that built in.

8

Why do you need to do the maths when you take the sample?
Simply log the parameters of the calculation, and then have the maths performed when you analyse the data, by a processor that is (almost certainly) better suited to it.
If you don't bother with a socket, and solder direct to the connectors, you may well find a cheap (look around your old MP3 player or cameras) SD card offers much lower cost than serial EEPROM, and much higher capacity.