Send data from one Raspberry Pico to another by use of REYAX RYLR998 UARTs. There are two boards. One sender board and one receiver board. Each board has two modules placed on it: One Raspberry Pico and one REYAX RYLR998 UART. These two modules are connected in exactly the same way on both boards (pls. refer to the "Drawing.JPG" file). The only difference is in the software. The sender will run stand-alone, while the receiver is waiting to receive and display the data, once they come in.
On the receiver board the following files should be loaded in the main directory:
UART_check.py - This is to check the UART interface and the communication between the two modules on the same board, once they are connected.
INIT_Receiver.py - This will initiate the Pico UART and the RYLR998 module after power up.
RUN_Receiver.py - This will run the receiver board in an endless loop. It will wait for data to come in and display them on the computer screen.
On the sender board the following files should be placed in the main directory: UART_check.py - This is to check the UART interface and the communication between the two modules once they are connected. RUN_Sender.py - This one should be renamed to main.py once all initial tests are successfully completed. Then it can rund as a stand-alone device. Z_Numbers.txt - This is the text file, which contains the data, that will be read line per line and sent over the channel.
In this exercise we will experience how data can be transported from one Raspberry Pico to another Raspberry Pico. Data will be sent across via two REYAX RYLR998 UART modules, by use of the LoraWAN protocol. One board is configured as the "sender" and the other as the "receiver".
The LoraWAN transfer protocol allows for much greater distances compared to Bluetooth or WiFi. This is very useful for IoT projects. There are some limitations with bandwidth, so large data files cannot be sent over. But for small data amounts (like for sensors) Lora is very well suited.
In this example there are no sensors. All data is taken from a local text file (Z_Numbers.txt), which contains an indexed list of random 2-digits integer numbers. These records will be sent over the LoraWAN channel line by line, until all lines are transfered. Then the sender program just terminates.
Programs are kept very short and simple, such that also beginners will quickly unerstand and can start experimenting without running into too many troubles.
Here are the recommended steps to follow:
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Place two Raspberry Picos (I use Raspberry Pico W, but a normal Pico should also work...) on two seperate bread boards together with one REYAX RYLR998 UART, each.
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Load Micropython on both Pico boards. More information can be found on the https://micropython.org/ web site.
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Connect all jumper cables (as illustrated in the drawing - see "Drawing.JPG" file).
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Load the following programs on the receiver board: UART_check.py, INIT_receiver.py and RUN_receiver.py.
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Load the following programs on the sender board: UART_check.py, RUN_sender.py and Z_Numbers.txt.
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Test sender and receiver boards by entering simple AT commands on each board (make use of the UART_check.py program for that).
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On the receiver board start first the INIT_receiver.py program and once successfully finished, run the RUN_receiver.py program.
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Leave the receiver board alone. It will continue running and will wait until it receives some data from the sender board.
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On the sender board save the RUN_sender.py program as "main.py" on the Pico. It will automatically execute once re-connected.
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Now, disconnect the sender board and let it run autonomously (without computer), by simply connecting it to a power source (USB hub).
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Wait a few seconds....
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The sender should now propagate 5 bytes of data every few seconds. This will continue until the last line of the text file has been processed.
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On the sender board a quick LED flashing light indicates, that the sending process is ongoing. The receiver should now show the data received.
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Have fun!!
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Good luck.
One last hint: The programming of the internal LED is different for a Pico and a Pico W. For the Pico the initializaton is: led_onboard = Pin(25, Pin.OUT) For the Pico W the initializaton is: led_onboard = Pin("LED", Pin.OUT) Therefore a small adjustment in the code might be necessary if you run a normal Raspberry Pico device and not a Raspberry Pico W.