The OpenKontrolGateway a board like an Arduino Uno, but with a SD card interface, three RF board interfaces, an Ethernet board module slot and a DS1307 Real Time Clock with battery backup. It’s a nice collection of all the stuff you need to make a datalogger.
The OKG bundle at £25 gives you everything needed to box it up but I added the RTC kit and SRAM which added £12 to the cost, since a data logger without an RTC is always going to be a pain, where you have to connect up a PC to set it. That’s OK at home but no fun at the farm.
The RTC gave me a hard time right off the bat. There are a few gotchas.
- You have to set the damn thing,
- you need to do that to even see it started, since it can need initialisation from the SPI bus before the oscillator will start
- You need a 2032 coin cell present for it to be able to work too, so no testing that without and thinking you’ll fit that later 😉
So if you ‘scope the crystal and think ‘ah, that’s why it isn’t working’ then not so fast, you may need to initialise and set it before you see any action there. I found all of this out the hard way. This is what I used to set it, which I largely pinched from LadyAda’s tutorial. One of the nice things about that is it lets you set the clock to the time the sketch was compiled, which save a whole load of faff. What you must not do then is to press reset, or switch off and on again, else it will do that all over again, setting the RTC back to the time it was compiled. You must comment out the line
// RTC.adjust(DateTime(__DATE__, __TIME__));
and re-upload it. This listing has that line commented out, so you must uncomment it to set the clock, then recomment it.