Import YEEP-144 library 1.2 sources

Source-only snapshot of the 1.2 release. Drivers/ (the vendored ST HAL and
CMSIS) is excluded at 173 MB; fetch it from STMicroelectronics/STM32CubeH5 to
build.

yeepi.py

@@ -0,0 +1,67 @@
+import spidev
+import RPi.GPIO as GPIO
+
+global spi
+
+PISPI_BUFFER_SIZE = 256 # Buffer size must match between Pi and STM32
+
+# Pin number for our CS pin repurposed as a ready pin
+ReadyPin = 8
+
+# Initialise the SPI communications
+# You must pass in the pigpio handle
+# Speed is optional, defaults to 1MHz
+def YEEPiInit(speed=1000000):
+    
+    # Global these so they can be used later
+    global spi
+    
+    spi = spidev.SpiDev() # Create SPI object
+    spi.open(0,0) # Open SPI bus 0 device 0
+    spi.max_speed_hz = speed # Set speed to inputted speed
+    spi.mode = 0 # Set SPI mode to 0
+    spi.no_cs = True # Disable chip select
+    
+    GPIO.setmode(GPIO.BCM)
+    GPIO.setup(ReadyPin, GPIO.IN, pull_up_down=GPIO.PUD_OFF)
+
+
+# Execute a transfer to YEEP, exchanging buffers
+# Takes a bytearray of values and returns a bytearray
+# with the received data
+#
+# Input data smaller than the buffer size will be padded to correct size
+# with null bytes. Input data larger will be truncated
+# Warnings will be printed in the cases of an array being truncated
+# or if received data is blank
+  
+def YEEPiTransfer(TXBuf):
+    # Check that the input data is a byte array, error if not
+    if not isinstance(TXBuf, bytearray):
+        raise TypeError("Data must be byte array")
+    
+    # Check if the array is larger, and delete extra entries
+    if len(TXBuf) > PISPI_BUFFER_SIZE:
+        print("Warning: Array larger than buffer size, truncating")
+        del TXBuf[PISPI_BUFFER_SIZE:] # Delete entries beyond buffer size
+    
+    # Pad the array to the full size if required
+    TXBuf = TXBuf.ljust(PISPI_BUFFER_SIZE, b'\0') #Pad to buffer size with null bytes
+    
+    # Wait until ready pin is asserted
+    while not GPIO.input(ReadyPin):
+        pass # Pass immediatly restarts the loop with no delay - we don't want to wait any longer than we have to
+    
+    # Execute the transfer
+    RXBuf = spi.xfer(TXBuf)
+    
+    # If the received buffer is all 0, warn the user
+    if sum(RXBuf) == 0:
+        print("Warning: Empty message received")
+    
+    # Convert returned list to bytearray
+    return bytearray(RXBuf)
+    
+# This should be called when the program exits    
+def YEEPiExit():
+    GPIO.cleanup()