I have 3-6 microcontrollers, up to 2m apart. One of them is designated the server and will be fed sensor data from the others, at least at 100 Hz. (Each data point is just a couple of bytes)
Since the microcontrollers move around, I can't connect them with wires. What's a good wireless solution here?
My initial idea was Bluetooth, mainly because that's the one solution I'm familiar with, but Bluetooth consumes much power (my circuits will be battery-powered) and Bluetooth modules are expensive.
Best Answer
For communicating within a couple of meters range, these nRF24L01+ modules, at around $1.42 apiece on eBay, would suit the requirements:
The module has a PCB trace antenna, which does a pretty reasonable job.
The range seems to be stable at around 6-7 meters during the day, and I have occasionally seen as much as 20-25 meters late at night when most other electronic devices in the vicinity are off.
Sparkfun sells a similar module but with an SMA connector for an external antenna, which claims as much as 100 meters range at 250 kbps data rate. Of course, at nearly $20 plus the cost of an antenna, that may be overkill for the required 2 meter range.
Relevant to the specific application:
The key improvement of the nRF24L01+ over the now obsolete nRF24L01 is the implementation of an auto-retransmit feature, which addresses the collision detection complexity concern raised in comments on the question.