Thank you very much. I DID IT !
Thanks to the Serial Input Basics tutorial and your advices, I managed to send my message using a Python code through the NRF modules, from one Arduino to another. Here's a little sum up of what I understood, if it can help other beginners :
- The Arduino runs in full autonomy with its uploaded sketch, and cannot interact with data on your computer
- You need to use a program to do so, using a programming language (here : Python)
- The tool allowing the communication between the computer and the Arduino is the "Serial monitor" (available in the Arduino IDE : Tools/Serial Monitor)
- The Python program will simulate the use of the Serial Monitor. The Arduino needs a downloaded sketch to use the data sent with the program
- Once the program is running, everything happens in the program. If Python commands to write in the Serial Monitor, the only way to see the message is Python commanding to print what's on the Serial monitor. Every interaction must be in the same program
- Basically use the code given in the Serial Input Basics Tutorial (previous answer) for your Arduino to deal with Serial Inputs.
Here 's my code, I think it can be helpful :
ArduinoUno = serial.Serial(port="COM3", baudrate=9600, bytesize=8, timeout=2, stopbits=serial.STOPBITS_ONE)
ArduinoNano = serial.Serial(port="COM4", baudrate=9600, bytesize=8, timeout=2, stopbits=serial.STOPBITS_ONE)
file = open('message.txt', 'r')
message = file.read() + '\n'
bits = 
chaine = ''
for i in range(len(message)//8 + 1) :
chaine = ''
chaine += message[8*i:8*i+8]
while True :
for i in range(len(bits)):
As you can see, I take my message in a txt file. I add '\n' because the downloaded sketch understands it as the end-of-line marker.
The maximum 'bytesize' length is 9. It will, therefore, cut every character further than the 8th position in a message sent to/from the serial monitor. Here's my syntax to end with the full original message, no matter its length.
For the question of the NRFs in particular, You can easily find a code to communicate with the NRFs on the web, and easily mix it with the codes in the Serial Input Basics tutorial. I'm not sure uploading these sketches, which are quite long though almost only literal copy/paste would be relevant, but do not hesitate to ask.
Thanks so much to everyone who took the time to answer me !