Hello,
I'm going to try this experiment to learn uC development.
I would like to build a simple system with two boards.
The first board collects date and time of an on-off signal (20 reads a day) that will be transferred over Zigbee to the other board. If Zigbee connection is not available, data are temporarily buffered into the eeprom of arduino.
The second board will be equipped with another Zigbee receiver and will be used to receive the data, store them on an SD card and when connected to a PC, data will be transferred.
The boards must be equipped with an Xbee shield for communication and a proto-shield with the RTC logic for the first board and the SD Card interface for the second bord: is this possible, or the Xbee shield doesen't allow another shield to be mounted ?
Does this kind of application sounds possible to realize with two simple Duemilanove ?
What kind of accuracy do you need for the RTC? If you periodically set the
time on the Arduino the Arduino could track the time using the counter timer and an interrupt. This would save you a RTC circuit.
Since I do not the details of your system these ideas may not make sense --
Could the Arduino that is tracking the events have the SD card?
Could the Arduino that is tracking the events transmit to a PC that
has an XBee interface attached? If the PC wasn't available then the
data would be cached.
I make a single board uC system, the ZB1, that has an ATmega168 + XBee.
I burn the Arduino bootloader and use the Arduino tools to program it.
You would need do add the RTC and SDC using the expansion connector.
I also have a protoboard and an LCD board.
The datasheet and schematic are at Loading...
One board, call it the Satellite, must be cheap, and must log data on your own to be sent to the master board.
Must have an RTC with a backup battery, so in case of a power failure, date and time are retained.
Must have a little local buffer, in case of unavailability of the master board.
The other board, call it the Master, have to receive the data from the satellite, and store them on an SD card for further reading.
Tha last part is a PC that connects to the master board (locally via USB or using a Zigbee interface) when I need to work with the data stored on the SD Card.
Your original question was "Does this kind of application sounds possible to realize with two simple Duemilanove ?"
There are a number of ways I could see to do this with Arduino compatible boards.
As was mentioned you may want to check out the capabilities of the XBee. You may
be able to add a RTC and have it be the satellite node.
If you added a battery to the Arduino the Arduino could switch to a low power
operating mode on power failure and just maintain the RTC counts. Could save you some money on the satellite. This is what I do in some MSP430 designs.
It sounds like there is no chance to make the PC the master.
If you are able to do a RTC using low-power mode and work through details
like the interrupt servicing in low-power mode please post back to the list if
possible.
I am curious about the details. This kind of thing is trivial on an MSP430.
I am interested in seeing the differences between the two devices.