Temperature-Sensor Network with RTC and LCD Part II

XBee on perfboard

Part II of the temperature-sensor network starts with the Base Station.
The XBee Series 2 sitting on the base station connected to the Arduino UNO is configured in Coordinator API mode. I use the following settings (all other settings are the default Coordinator API setttings of the firmware) which are programmed via the X-CTU software from digi:

•  AT ID 2001 (PAN ID) (see #1)
•  AT DH 0 (see #2)
•  AT DL 0 (see #2)
•  AT AP 1 (see #3)
•  AT SP AF0 (see #4)

1. The extended PAN ID for my network (AT ID = 2001) is 2001 (I hope it will be no "Space Odyssey" though)  - but you can take any 64-bit value up to 0xFFFFFFFFFFFFFFFF or even leave it to 0 where the Coordinator would select a random PAN ID. Be sure to set the same ID to the other devices which should join the network.
2. The Destination High and Low Address is both set to 0 (AT DH = 0, AT DL =  0) which defines the coordinator.
3. API mode (AT AP) is set to enable (=1) because we want to receive and parse packets instead of just routing the traffic via the serial port like you would do in transparent mode.



Perfboard back side




4. The last setting is for the sleep period according to longest sleep period on a/ the End Device(s) (AT SP = AF0). This is to take care that the Coordinator (or any Router which is configured to this length of sleep period) will buffer the messages for the End Device long enough to get them transferred when the End Device awakens (no snooze allowed!). The sleep period is set to 28 seconds on my End Device because the sleep period is multiplied by 10 the value is 2800ms in Decimal or AF0 in Hex.

Unfortunately and for the sake of formality I have to say that my wiring seen in the following picture could be of risk to damage your XBee! As the Arduino UNO runs on 5 volts and the level on the TX pin (digital pin 1) is about 5 volts when HIGH, the DIN pin of the XBee (pin 3) could be exposed to more power than allowed. So I give no guarantee that your XBee is as robust as mine - take care of it and use a level shifter in any case!

XBee with level shifter

Update: For the last days I tested a very simple level shifter, which works for me. I have very low traffic though and there may be problems with higher data transmit rates, but for the time being I just added two resistors (22kohm and 33kohm) as a simple voltage divider and now have maximum roughly 3 volts on DIN of the XBee. So that may be a quick workaround.



Part III will continue with the base station.