adding examples for microsd bff

Adding a read and write example for the microsd bff

microSD_BFF_Examples/read_sd/code.py

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+# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
+# SPDX-License-Identifier: MIT
+
+import os
+import busio
+import digitalio
+import board
+import storage
+import adafruit_sdcard
+
+# The SD_CS pin is the chip select line.
+
+SD_CS = board.TX  # setup for microSD BFF
+
+# Connect to the card and mount the filesystem.
+spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
+cs = digitalio.DigitalInOut(SD_CS)
+sdcard = adafruit_sdcard.SDCard(spi, cs)
+vfs = storage.VfsFat(sdcard)
+storage.mount(vfs, "/sd")
+
+# Use the filesystem as normal! Our files are under /sd
+
+# This helper function will print the contents of the SD
+def print_directory(path, tabs=0):
+    for file in os.listdir(path):
+        stats = os.stat(path + "/" + file)
+        filesize = stats[6]
+        isdir = stats[0] & 0x4000
+
+        if filesize < 1000:
+            sizestr = str(filesize) + " bytes"
+        elif filesize < 1000000:
+            sizestr = "%0.1f KB" % (filesize / 1000)
+        else:
+            sizestr = "%0.1f MB" % (filesize / 1000000)
+
+        prettyprintname = ""
+        for _ in range(tabs):
+            prettyprintname += "   "
+        prettyprintname += file
+        if isdir:
+            prettyprintname += "/"
+        print("{0:<40} Size: {1:>10}".format(prettyprintname, sizestr))
+
+        # recursively print directory contents
+        if isdir:
+            print_directory(path + "/" + file, tabs + 1)
+
+
+print("Files on filesystem:")
+print("====================")
+print_directory("/sd")

microSD_BFF_Examples/write_to_sd/code.py

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+# SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+import time
+import adafruit_sdcard
+import board
+import busio
+import digitalio
+import microcontroller
+import storage
+
+# default CS pin for the microSD bff is TX
+SD_CS = board.TX
+
+# Connect to the card and mount the filesystem.
+spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
+cs = digitalio.DigitalInOut(SD_CS)
+sdcard = adafruit_sdcard.SDCard(spi, cs)
+vfs = storage.VfsFat(sdcard)
+storage.mount(vfs, "/sd")
+
+# Use the filesystem as normal! Our files are under /sd
+
+print("Logging temperature to filesystem")
+# append to the file!
+while True:
+    # open file for append
+    with open("/sd/temperature.txt", "a") as f:
+        t = microcontroller.cpu.temperature
+        print("Temperature = %0.1f" % t)
+        f.write("%0.1f\n" % t)
+    # file is saved
+    time.sleep(1)