NRF24L01+
The antennas arrived!
Another layer of abstraction: Libraries.
First, I'm going to use the RF24 library by TMRh20 in the Arduino IDE. After which, if time permits, I'll learn to work with the NRF24L01 datasheet and do some low-level programming. For now, I just need to make sure these antennas work and understand the fundamentals.
I'll be using this tutorial to introduce me:
https://howtomechatronics.com/tutorials/arduino/arduino-wireless-communication-nrf24l01-tutorial/
I followed the instructions above, yet couldn't get the simple program to work: One antenna sends the message "Hello World!" And the receiver displays the message on the serial output in the Arduino IDE.
One comment the above link makes is that the nRF24L01+ is very sensitive to power fluctuations. I plugged in my Analog Discovery 2 (USB oscilloscope) and discovered this pattern:
Better, but somehow the problem persists.
I also discovered that this pattern is caused by the antenna module itself. Any time it sends a signal, the Arduino doesn't seem capable of supplying enough power. Let's test this theory by increasing the transmission rate from 1s to 10 messages per second.
That seems to be the case.
Something else I discovered: Since the antenna draws so much current, a typical 9 V battery isn't good enough. I tested my voltmeter on the power supply and it dropped from 8 V all the way down to 5.5 V. When I mount this antenna in my controller, we'll need to make sure the battery can handle the current demands.
Let's try to do everything we can to smooth out power. Below I have an external power source with two decoupling capacitors (low cap and high cap) to smooth out high frequency and low frequency fluctuations:
That helped some. But didn't solve the problem. Transmission still doesn't work and there are still some noticeable fluctuations. nRF24 seems to be highly sensitive to power noise. Let's figure this out.
6+ hours later
After adding an external power supply, capacitors, and trying just about everything (and testing the connection between the Arduino's and antennas and verifying a solid connection), I have concluded we need an even more stable power supply that can draw 200mA+ current (did a Google search to see the current demands). We'll need a voltage regulator:
I went with the LD1117V33 voltage regulator to output a steady 3.3 V (max for the antenna) and can draw up to 800 mA of current. Since the voltage dropout at 800 mA is only 1.2 V, I'll only need 4.5 V to power it, which is totally doable.
It'll arrive May 27th! In the meantime, I still want to practice interfacing with Brandon's on-board Arduino....