What module to purchase

cjkogan111

Hello,
I am not sure exactly what I should purchase: Basic Stamp 2, Propeller Chip or the Javalin Chip.
I want want to use the chip to take periodic data from different instruments in various ways. For instance, I might want temperature measurements every 5 minutes, I might want pressure measurements when the user presses a certain button etc.
I would like enough space to store temperature measurements every 5 minutes for a week, however, if this is too difficult, temperature measurements every 5 minutes for 3-4 hours would suffice.
I want the temperature measurements to be stored with the exact time. Prefereably I would like to synchronize the time with a computer when I hook it up. The number of seconds after being initialized would suffice though.
Thanks!
-cjkogan111

Mike Green

Your measurements are relatively infrequent. You have 12/hour which is roughly 300/day or 2100/week. That's 2 bytes for the data and 3 to 4 bytes for a time stamp for a total of roughly 13K. I'd recommend the BS2pe model which has 32K of EEPROM available for program and data in 2K "slots". Your program would probably fit easily in one slot leaving 30K for data logging, enough for the temperature information and other, less frequent data. The BS2pe is also pretty low powered. It can take a set of measurements and go to sleep until the next measurement is to be taken. It could also sleep for shorter periods of time, awakening to check pushbuttons or other signals for other logging requests. I'd suggest using a DS1307 real time clock with a battery backup. SparkFun Electronics has a nice "breakout board" complete with the clock, backup battery, and crystal. This would let you accurately time stamp the data. There's plenty of sample code in the Nuts and Volts Columns from Parallax.

If 32K isn't enough, you can always attach another I2C EEPROM to a pair of I/O pins (0/1 or 8/9). These come as large as 128K these days. You can set them to different addresses and have a total of 4 x 128K = 512K attached to one pair of I/O pins.

Post Edited (Mike Green) : 12/30/2008 6:42:35 AM GMT

cjkogan111

Thanks Mike!