add fixed circuitpython code for feather board + readme note

Author: jrpear

README.md

@@ -83,6 +83,10 @@ On the board you want to receive data, make sure you have CircuitPython installe
 
 Once you have CircuitPython running, upload the files from the ```circuit-python-lora-passthrough``` folder in this repo. Make sure to overwrite any existing ```boot.py``` and ```code.py``` files on your CircuitPython board with the ones from this folder.
 
+> [!NOTE]
+> If you're targeting a Feather rather than a flight controller board, then
+> copy `feather\_code.py`
+
 ```boot.py``` enables both virtual serial ports that the device presents over USB. This allows you to use one for the console and one for data. ```code.py``` acts as a LoRa radio forwarder over USB serial: The console port is used for logging and debugging, and is the first serial port that appears when the board is connected. The data port is used for actual data transfer, and is the second serial port.
 
 1. Open the console port on your computer. This is the first serial port that opens when you plug in the circuitpython board. It should start by printing:

circuit-python-lora-passthrough/feather_code.py

@@ -0,0 +1,41 @@
+"""
+CircuitPython Feather RP2350 LoRa Radio forwarder
+
+This code will forward any received LoRa packets to the serial console (sys.stdout). It cycles through neo pixel colors
+to indicate packet reception.
+"""
+
+import time
+
+import adafruit_rfm9x
+import board
+import digitalio
+import usb_cdc
+
+# Radio constants
+RADIO_FREQ_MHZ = 437.4
+CS = digitalio.DigitalInOut(board.RFM9X_CS)
+RESET = digitalio.DigitalInOut(board.RFM9X_RST)
+
+rfm95 = adafruit_rfm9x.RFM9x(board.SPI(), CS, RESET, RADIO_FREQ_MHZ)
+rfm95.spreading_factor = 8
+rfm95.signal_bandwidth = 125000
+rfm95.coding_rate = 5
+rfm95.preamble_length = 8
+# time_start = time.time()
+packet_count = 0
+print("[INFO] LoRa Receiver receiving packets")
+while True:
+    # Look for a new packet - wait up to 2 seconds:
+    packet = rfm95.receive(timeout=2.0)
+    # If no packet was received during the timeout then None is returned.
+    if packet is not None:
+        usb_cdc.data.write(packet)
+        packet_count += 1
+    # time_delta = time.time() - time_start
+    # if time_delta > 10:
+    #     print(f"[INFO] Packets received: {packet_count}")
+    #     time_start = time.time()
+    data = usb_cdc.data.read(usb_cdc.data.in_waiting)
+    if len(data) > 0:
+        rfm95.send(data)