From f4a6ea896f711f68e898e69e21d74118a44465f2 Mon Sep 17 00:00:00 2001
From: jaseg <git@jaseg.net>
Date: Mon, 27 Jan 2020 21:58:22 +0100
Subject: serial basically working

---
 gm_platform/fw/crctest.py | 79 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 gm_platform/fw/crctest.py

(limited to 'gm_platform/fw/crctest.py')

diff --git a/gm_platform/fw/crctest.py b/gm_platform/fw/crctest.py
new file mode 100644
index 0000000..5c97be9
--- /dev/null
+++ b/gm_platform/fw/crctest.py
@@ -0,0 +1,79 @@
+custom_crc_table = {}
+
+def generate_crc32_table(_poly):
+
+    global custom_crc_table
+
+    for i in range(256):
+        c = i << 24
+
+        for j in range(8):
+            c = (c << 1) ^ _poly if (c & 0x80000000) else c << 1
+
+        custom_crc_table[i] = c & 0xffffffff
+
+
+def crc32_stm(bytes_arr):
+
+    length = len(bytes_arr)
+    crc = 0xffffffff
+
+    k = 0
+    while length >= 4:
+
+        v = ((bytes_arr[k] << 24) & 0xFF000000) | ((bytes_arr[k+1] << 16) & 0xFF0000) | \
+        ((bytes_arr[k+2] << 8) & 0xFF00) | (bytes_arr[k+3] & 0xFF)
+
+        crc = ((crc << 8) & 0xffffffff) ^ custom_crc_table[0xFF & ((crc >> 24) ^ v)]
+        crc = ((crc << 8) & 0xffffffff) ^ custom_crc_table[0xFF & ((crc >> 24) ^ (v >> 8))]
+        crc = ((crc << 8) & 0xffffffff) ^ custom_crc_table[0xFF & ((crc >> 24) ^ (v >> 16))]
+        crc = ((crc << 8) & 0xffffffff) ^ custom_crc_table[0xFF & ((crc >> 24) ^ (v >> 24))]
+
+        k += 4
+        length -= 4
+
+    if length > 0:
+        v = 0
+
+        for i in range(length):
+            v |= (bytes_arr[k+i] << 24-i*8)
+
+        if length == 1:
+            v &= 0xFF000000
+
+        elif length == 2:
+            v &= 0xFFFF0000
+
+        elif length == 3:
+            v &= 0xFFFFFF00
+
+        crc = (( crc << 8 ) & 0xffffffff) ^ custom_crc_table[0xFF & ( (crc >> 24) ^ (v ) )];
+        crc = (( crc << 8 ) & 0xffffffff) ^ custom_crc_table[0xFF & ( (crc >> 24) ^ (v >> 8) )];
+        crc = (( crc << 8 ) & 0xffffffff) ^ custom_crc_table[0xFF & ( (crc >> 24) ^ (v >> 16) )];
+        crc = (( crc << 8 ) & 0xffffffff) ^ custom_crc_table[0xFF & ( (crc >> 24) ^ (v >> 24) )];
+
+    return crc
+
+poly = 0x04C11DB7
+buf = bytes(reversed([1, 2, 3, 4]))
+
+generate_crc32_table(poly)
+print(hex(crc32_stm(bytearray(buf))))
+
+from crccheck import crc
+import struct
+
+def rev_bits_in_word(w):
+    return sum( ((w>>i)&1) << (31-i) for i in range(32) )
+
+import zlib
+def crc32stm(inbytes):    
+    crc32 = crc.Crc32.calc(inbytes)^0xffffffff
+    #crc32 = zlib.crc32(inbytes)^0xffffffff
+    crc32 = rev_bits_in_word(crc32)
+    return crc32
+
+#data = [0x80,0x40,0xc0,0x20]
+data = [0x00, 0, 0, 0x80, 0, 0, 0, 0x80]
+print(hex(crc32stm(bytes(data))))
+print(hex(zlib.crc32(bytes([0, 0, 0, 1]))^0xffffffff))
-- 
cgit