def receive(conn):
"""
Attempt to read messages from a serial connection
"""
data = bytearray()
while True:
buf = conn.read(READ_BYTES)
if buf:
if DEBUG: print(">>> RAW RECEIVE:", buf)
data.extend(buf)
if (not buf) or len(buf) < READ_BYTES:
break
idx = 0
while idx + 9 <= len(data):
if data[idx] != STX:
idx += 1
continue
stx, req, addr, size = struct.unpack('>BBBB', data[idx:idx + 4])
if req not in (ENQ, ACK, NAK):
print(
"Bad req value: {:02x} (should be one of ENQ/ACK/NAK)".format(
req))
idx += 1
continue
if idx + 4 + size >= len(data):
print("Can't read %d bytes from buffer" % size)
idx += 1
continue
msg, lsb, msb, etx = struct.unpack('>%dsBBB' % size,
data[idx + 4:idx + 7 + size])
if etx != ETX:
print("Bad ETX value: {:02x}".format(etx))
idx += 1
continue
crc_calc = crc16.calcData(data[idx + 1:idx + 4 + size])
crc_msg = msb << 8 | lsb
if crc_calc != crc_msg:
print("Bad CRC check: %s <> %s" %
(binascii.hexlify(crc_calc), binascii.hexlify(crc_msg)))
idx += 1
continue
if DEBUG:
print(">>> RECV:", binascii.hexlify(data), "=>",
binascii.hexlify(msg))
yield {
"stx": stx,
"req": req,
"addr": addr,
"size": size,
"msg": msg,
"lsb": lsb,
"msb": msb,
"etx": etx,
}
idx += 4 + size
def send(conn, req, cmd, subcmd, data=b'', addr=1):
"""
Send cmd/subcmd (e.g. 0x60/0x01) and optional data to the RS485 bus
"""
assert req in (ENQ, ACK, NAK) # req should be one of ENQ, ACK, NAK
msg = struct.pack('BBBBB', req, addr, 2 + len(data), cmd, subcmd)
if len(data) > 0:
msg = struct.pack('5s%ds' % len(data), msg, data)
crcval = crc16.calcData(msg)
lsb = crcval & (0xff)
msb = (crcval >> 8) & 0xff
data = struct.pack('B%dsBBB' % len(msg), STX, msg, lsb, msb, ETX)
if DEBUG: print(">>> SEND:", binascii.hexlify(msg), "=>", binascii.hexlify(data))
conn.write(data)
conn.flush()
def send_request(connection, inv_id, cmd):
""" Send command (e.g. b'\x60\x01') to the inverter with id inv_id """
# Borrowed from DeltaPVOutput
length = len(cmd)
msgbody = struct.pack('BBB%ds' % length, 5, inv_id, length, cmd)
crcval = crc16.calcData(msgbody)
lsb = crcval & (0xff)
msb = (crcval >> 8) & 0xff
data = struct.pack('BBBB%dsBBB' % length, 2, 5, inv_id, length, cmd, lsb,
msb, 3)
if debugging:
print("Sending data query to inverter", inv_id)
connection.write(data)
connection.flush()
def decode_response(data):
"""
Try to decode an inverter-messages from serial data and return
a dictionary with message parameters (including length, inverter_id,
command, subcommand).
Checks message validity, consistency and CRC, and returns None
if a message is not valid. Request-messages are parsed, but are
currently not returned.
"""
try:
stx = data[0]
enqack = data[1]
if stx != 0x02:
if verbose:
print("Invalid message, STX =", stx)
return None
if enqack != 0x05 and enqack != 0x06:
if verbose:
print("Invalid message, ENQ/ACK =", enqack)
return None
inv_id = data[2]
length = data[3]
if (
len(data)
) < length + 4 + 3: # should be 4 bytes (STX + ACK + ID + LEN) + data length + 3 bytes (CRC16 + ETX)
if verbose:
print("Incomplete data block of", len(data),
"bytes, should be", length + 7, "bytes")
return None
cmd = data[4] # Command ID
subcmd = data[5] # Subcommand ID
data_offset = 6 # Start of data
data_length = length - 2 # Length of data
crc_lsb = data[
4 +
length] # Least-significant byte of CRC-16 over preceding bytes after STX
crc_msb = data[
4 + length +
1] # Most-significant byte of CRC-16 over preceding bytes after STX
etx = data[4 + length +
2] # ETX-byte to signify end of message, should be 0x03
rvals = {'enqack': enqack, 'inv_id': inv_id, 'length': length, 'cmd': cmd, 'subcmd': subcmd, \
'data_offset': data_offset, 'data_length': data_length}
if etx != 0x03: # ETX isn't 0x03, data probably isn't valid
if verbose:
print("ETX at", length + 2, "is", etx, "but should be 3")
print(rvals)
return None
else: # ETX is 0x03, we probably have a valid data block
crc_calc = crc16.calcData(
data[1:4 +
length]) # Calculate CRC-16 over message, excluding STX
crc_msg = crc_msb << 8 | crc_lsb # Compare with CRC transmitted at end of message
if crc_calc != crc_msg:
print("WARNING: CRC-16 is", hex(crc_calc), " but should be",
hex(crc_msg))
return None
else:
if enqack == 0x05: # ENQ, marks start of request message
if debugging:
print("Found request-message for inverter", inv_id,
"with length", length, "and CMD", cmd, "SUB",
subcmd)
return None # Currently we do not return requests, only replies
if debugging:
print("Found valid response:", rvals)
return rvals
except:
print("Error decoding response:", str(sys.exc_info()[0]))
return None