Extract reusable device protocols, ports and logic analyzers from SETGUI

python/logic_analyzer/decoders/pm35_uart.py

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+"""PM35 MODBUS 03/06, including the legacy 128-word/zero-byte-count reply."""
+from .set_uart import crc16, number
+
+
+def parse_pm35(raw, role):
+    raw = bytes(raw)
+    if len(raw) < 5:
+        raise ValueError('Incomplete PM35 frame')
+    if crc16(raw[:-2], True) != number(raw[-2:]):
+        raise ValueError('PM35 CRC mismatch')
+    address, function = raw[:2]
+    result = dict(protocol='PM35', controller=address, function=function, raw=raw)
+    if function in (0x83, 0x86):
+        if len(raw) != 5 or role == 'request':
+            raise ValueError('Invalid exception response')
+        result['summary'] = 'PM35 node=%d exception fn=%02X code=%d' % (address, function, raw[2])
+    elif function == 6 or function == 3 and role == 'request':
+        if len(raw) != 8:
+            raise ValueError('PM35 request/06 must contain 8 bytes')
+        register, value = number(raw[2:4], 'big'), number(raw[4:6], 'big')
+        if register >= 128 or function == 3 and not 1 <= value <= 128 - register:
+            raise ValueError('PM35 register range outside 0..127')
+        result.update(register=register, value=value)
+        result['summary'] = 'PM35 node=%d %s R%d %s=%d' % (address,
+            'READ' if function == 3 else 'WRITE/echo', register,
+            'count' if function == 3 else 'value', value)
+        if function == 6 and register == 127:
+            result['summary'] += ' command_bits=%04X' % value
+    elif function == 3:
+        count = raw[2] or 256
+        if count % 2 or len(raw) != count + 5:
+            raise ValueError('Invalid PM35 response byte count')
+        result['values'] = [number(raw[i:i+2], 'big') for i in range(3, len(raw)-2, 2)]
+        result['summary'] = 'PM35 node=%d READ response %d words: %s' % (address,
+            len(result['values']), ' '.join('%04X' % v for v in result['values']))
+    else:
+        raise ValueError('Unsupported PM35 function')
+    return result
+
+
+class PM35Parser:
+    def __init__(self, role):
+        self.role = role
+        self.buffer = []
+
+    def flush(self):
+        if not self.buffer:
+            return []
+        ss, es = self.buffer[0][1], self.buffer[-1][2]
+        self.buffer = []
+        return [(ss, es, None, 'Incomplete PM35 frame')]
+
+    def feed(self, value, ss, es):
+        self.buffer.append((value, ss, es))
+        events = []
+        while len(self.buffer) >= 3:
+            raw = bytes(item[0] for item in self.buffer)
+            fn = raw[1]
+            if fn not in (3, 6, 0x83, 0x86):
+                del self.buffer[0]
+                continue
+            role = self.role
+            total = 5 if fn & 128 else 8
+            if role == 'auto' and fn == 3:
+                candidates = [(8, 'request'), ((raw[2] or 256) + 5, 'response')]
+                found = None
+                for length, candidate_role in candidates:
+                    if len(raw) >= length:
+                        try:
+                            found = (length, candidate_role, parse_pm35(raw[:length], candidate_role))
+                            break
+                        except ValueError:
+                            pass
+                if found:
+                    length, candidate_role, result = found
+                    events.append((self.buffer[0][1], self.buffer[length-1][2], result, None))
+                    del self.buffer[:length]
+                    continue
+                if len(raw) < max(length for length, _ in candidates):
+                    break
+                events.append((self.buffer[0][1], self.buffer[-1][2], None, 'Invalid PM35 frame/CRC'))
+                del self.buffer[0]
+                continue
+            if fn == 3 and role == 'response':
+                total = (raw[2] or 256) + 5
+            if len(raw) < total:
+                break
+            result, error = None, None
+            try:
+                result = parse_pm35(raw[:total], role)
+            except ValueError as exc:
+                error = str(exc)
+            events.append((self.buffer[0][1], self.buffer[total-1][2], result, error))
+            del self.buffer[:1 if error else total]
+        return events