adding software spi and spi hw/sw autodetection

lib/oven.py

@@ -7,6 +7,7 @@ import config
 import os
 import digitalio
 import busio
+import bitbangio
 import statistics
 
 log = logging.getLogger(__name__)
@@ -117,9 +118,29 @@ class TempSensorReal(TempSensor):
         TempSensor.__init__(self)
         self.sleeptime = self.time_step / float(config.temperature_average_samples)
         self.temptracker = TempTracker() 
-        self.spi = busio.SPI(config.spi_sclk, config.spi_mosi, config.spi_miso)
+        self.spi_setup()
         self.cs = digitalio.DigitalInOut(config.spi_cs)
 
+    def hw_spi(self):
+        import board
+        if(hasattr(board,'SCLK') and
+           hasattr(board,'MOSI') and 
+           hasattr(board,'MISO')):
+            if(board.SCLK == config.spi_sclk and
+               board.MOSI == config.spi_mosi and
+               board.MISO == config.spi_miso):
+               return board.SPI();
+        return None
+
+    def spi_setup(self):
+        self.spi = self.hw_spi()
+        if self.spi is None:
+            self.spi = bitbangio.SPI(config.spi_sclk, config.spi_mosi, config.spi_miso)
+            log.info("Software SPI selected for reading thermocouple")
+        else:
+            log.info("Hardware SPI selected for reading thermocouple")
+
+
     def get_temperature(self):
         '''read temp from tc and convert if needed'''
         try: