I have been working with the 2.4Ghz nrf24L01 modules on a few projects. These modules are very inexpensive (about US $1.25 ea. when bought in quantities of 2 or more on eBay), and they seem to work well for short range, small payload data transmittal. This walk-through will show you how to wire them up, and then will demonstrate a pair of very basic sketches (one for the sender, and one for the receiver) used to verify that data is being sent wirelessly.
You will need (hardware):
(2) nrf24L01 2.4ghz wireless transcievers
(2) Arduino Uno (or compatible)
(2) LEDs: Red and Green (or whatever you have)
Recommended: male-female jumpers for connecting nrf24L01 modules to Arduino
You will need (software):
RF24 libraries by maniacbug (https://github.com/maniacbug/RF24)
The image below shows the view of the nrf24L01 from the top. Note: the pins are on the bottom-side. The image shows the top-side.
This drawing shows the basic connections from nrf24L01 to Arduino. For this sketch, the only difference between the sender and the receiver will be that two LEDs will need to be added on pins 3 and 5 (or whichever you choose, really).
Once you have the sender and receiver wired up, you will need to upload sketches to each. All the sender sketch does is send values 0 to 255 to the receiver, repeatedly.
On the receiver side, the sketch just reads the sent data and compares it to the last value received. If the value received is equal to the last value plus one, the green LED will light. If it is not, the red LED will light. This works pretty well to visually display how reliable the signal is. If you see lots of red, you know you are dropping packets. Note, though, that this sketch will blink the red LED once each cycle to indicate that a complete 0-255 cycle has taken place.
Again, the idea behind these two simple sketches is to get down to the most basic possible setup for use with nrf24L01. I hope this helps someone trying out the nrf24L01 transceivers for the first time. The video embedded below shows the behavior of the receiver when it experiences lost wireless packets.
Sketch for the sender:Sketch for the receiver: