add python script to calculate touch IC config CRC

gateware/drivers/touch.py

@@ -0,0 +1,41 @@
+#!/bin/python3
+
+CY8CMBR3xxx_CONFIG_DATA_LENGTH = 126
+CY8CMBR3xxx_CRC_BIT_WIDTH = 2 * 8
+CY8CMBR3xxx_CRC_BIT4_MASK = 0x0F
+CY8CMBR3xxx_CRC_BIT4_SHIFT = 4
+CY8CMBR3xxx_CCITT16_DEFAULT_SEED = 0xffff
+CY8CMBR3xxx_CCITT16_POLYNOM = 0x1021
+
+
+def CY8CMBR3xxx_Calc4BitsCRC(value, remainder):
+    # Divide the value by polynomial, via the CRC polynomial
+    tableIndex = (value & CY8CMBR3xxx_CRC_BIT4_MASK) ^ (remainder >> (CY8CMBR3xxx_CRC_BIT_WIDTH - CY8CMBR3xxx_CRC_BIT4_SHIFT))
+    remainder = (CY8CMBR3xxx_CCITT16_POLYNOM * tableIndex) ^ (remainder << CY8CMBR3xxx_CRC_BIT4_SHIFT)
+    return remainder
+
+
+def CY8CMBR3xxx_CalculateCrc(configuration):
+    seed = CY8CMBR3xxx_CCITT16_DEFAULT_SEED
+
+    # don't make count down cycle! CRC will be different!
+    for byteValue in configuration:
+        seed = CY8CMBR3xxx_Calc4BitsCRC(byteValue >> CY8CMBR3xxx_CRC_BIT4_SHIFT, seed) & 0xffff
+        seed = CY8CMBR3xxx_Calc4BitsCRC(byteValue, seed) & 0xffff
+
+    return seed
+
+
+with open("touch-cfg.hex", "r") as f:
+    xs = []
+    for line in f.readlines():
+        raw = line.strip()
+        v = int(raw, 16)
+        print("hex", raw, "int", v)
+        xs.append(v)
+    print("total bytes in file", len(xs))
+    xs = xs[2:-2]
+    print("bytes to crc", len(xs))
+    crc = CY8CMBR3xxx_CalculateCrc(xs)
+    print("crc0", hex(crc & 0x00FF))
+    print("crc1", hex((crc & 0xFF00)>>8))