drivers/sdcard/sdcard.py: Fixes per PR discussion.

Merged crc7.py into sdcard.py, fixed many little things per suggestions.
Removed hardwired crcs from cmd, always recompute.

Signed-off-by: Marcus Mendenhall <[email protected]>

Author: mendenm

micropython/drivers/storage/sdcard/sdcard.py

@@ -43,32 +43,12 @@
     b"\xe4\xd2\xc0\x1c\x0e8*TFpb\x8c\x9e\xa8\xba\xc4\xd6\xe0\xf2"
 )
 
-# ruff: noqa: F821 - @asm_thumb and @viper decorator adds names to function scope
-try:
-    from uctypes import addressof
-
-    @micropython.viper
-    def crc7(buf) -> int:
-        n = int(len(buf))
-        table = ptr8(addressof(crc7_be_syndrome_table))
-        bp = ptr8(addressof(buf))
-        idx = 0
-        crc = 0
-        while idx < n:
-            crc = table[crc ^ bp[idx]]
-            idx = idx + 1
-        return crc
-
-    # test to make sure this works!
-    # print(f"{crc7('abcde'):02x}")
-    assert crc7(b"abcde") == 0x34
-except:
-    # non-viper version if viper can'r be built
-    def crc7(buf) -> int:
-        crc = 0
-        for b in buf:
-            crc = crc7_be_syndrome_table[crc ^ b]
-        return crc
+
+def crc7(buf) -> int:
+    crc = 0
+    for b in buf:
+        crc = crc7_be_syndrome_table[crc ^ b]
+    return crc
 
 
 def gb(bigval, b0, bn):