Frequently Asked Questions¶
Are the RFM12B radios transmitters or receivers?¶
Transceivers. Each module can both receive and transmit information.
What is the range of the RFM12B radios?¶
Easy answer: 100 meters line of sight.
This is a bit of complicated question, since walls, floors, vegetation and other “non-line of sight” situations will decrease range. The lower frequency 434MHz radio modules can have a slightly longer range than 868MHz / 915MHz modules. Additionally, as the modules approach the edge of their ranges the error rates tend to go up, so it’s possible to transmit further with lower data rates and/or with reduced success of packets getting through.
Do the radios support broadcasting?¶
Yes, they support both one-to-many and many-to-one transmissions, in fact.
These schemes are implemented with two software parameters labelled nodeID and netGroup. Only nodes that are in the same netGroup can “hear” each other. netGroup 0 is a special case and can hear all the other groups. Unique nodeIDs (in the same netGroup) can all “hear” each other, but can filter conversations. Nodes can switch netGroup and nodeID numbers on the fly if this is needed.
How many nodes can I address at one time?¶
There are 31 possible nodeIDs, and 250 possible netGroups.
nodeID (1-31 are valid nodeID parameters)
> Node ID’s should be unique within the netGroup in which this node is operating. ID 31 is special because it will pick up packets for any node (in the same netGroup). ID 0 is also special, it is used to transmit in a special “OOK” format.
netGroup (1-250 are valid netGroup parameters)
> netGroup 0 is a special case and can hear all netGroup numbers.
Will nodes in different groups interfere with each other?¶
If they are on the same or a close by frequency, sadly, they will interfere with each other’s broadcasts, even though they can’t “hear” each other.
Is there collision detection built into the software?¶
Yes, but it’s pretty basic. It looks to see if the “air is clear” and then starts transmitting.
The JeeLabs software will not ask for a retransmit if a packet does not come through as expected. It has been designed with the primary application in mind being home automation, where the reading sensor values at some reasonably regular interval is more important than receiving every packet intact.
What is the power consumption of a JeeNode?¶
- ~35 mA sending
- ~19 mA receiving
- ~7 mA idle - radio off attending to other chores - but this will depend on the other chores.
- ~6 uA sleeping - with the full suite of power saving tricks implemented in JeeLabs software.
What is the operating voltage of all JeeLabs modules.¶
+3.3 volts everywhere apart from the JeeNode Micro series which use +3.0 volts as part of the overall power-saving strategy.
Aren’t you running ATmega’s out of spec at 3.3 V / 16 mHz¶
Yes, a little. It hasn’t seemed to be a problem with many thousands sold.
Are there low-power modes implemented in software?¶
How do I get support for my JeeNodes?¶
Support is through the “online user forum” http://jeelabs.net/projects/cafe/boards/