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[WIP] Add 485 deadtime enforcement #61

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[WIP] Add 485 deadtime enforcement #61

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74c23e2
Add 485 deadtime enforcement
altendky Dec 7, 2018
debd303
Fix use of time.monotonic() for py2 compatibility
altendky Dec 12, 2018
799b739
Make sure to wait at least the deadtime
altendky Dec 14, 2018
99685d1
Remove erroneous space
altendky Dec 14, 2018
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109 changes: 71 additions & 38 deletions sunspec/core/modbus/client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@
import struct
import serial
import sys
import time

try:
import xml.etree.ElementTree as ET
Expand All @@ -34,6 +35,10 @@

import sunspec.core.modbus.mbmap as mbmap


deadtime_clock = getattr(time, 'monotonic', time.clock)


PARITY_NONE = 'N'
PARITY_EVEN = 'E'

Expand All @@ -56,6 +61,16 @@ class ModbusClientTimeout(ModbusClientError):
class ModbusClientException(ModbusClientError):
pass


def wait_until(target, clock):
while True:
remaining = target - clock()
if remaining > 0:
time.sleep(remaining)
else:
break


def modbus_rtu_client(name=None, baudrate=None, parity=None):

global modbus_rtu_clients
Expand Down Expand Up @@ -148,6 +163,8 @@ def __init__(self, name='/dev/ttyUSB0', baudrate=9600, parity=None):
self.timeout = .5
self.write_timeout = .5
self.devices = {}
self.deadtime = 44 / int(self.baudrate)
self.last_receive_completion = -self.deadtime

self.open()

Expand Down Expand Up @@ -235,32 +252,40 @@ def _read(self, slave_id, addr, count, op=FUNC_READ_HOLDING, trace_func=None):
s += '%02X' % (ord(c))
trace_func(s)

wait_until(
target=self.last_receive_completion + self.deadtime,
clock=deadtime_clock,
)

self.serial.flushInput()
try:
self.serial.write(req)
except Exception as e:
raise ModbusClientError('Serial write error: %s' % str(e))

while len_remaining > 0:
c = self.serial.read(len_remaining)
if type(c) == bytes and sys.version_info > (3,):
temp = ""
for i in c:
temp += chr(i)
c = temp
try:
while len_remaining > 0:
c = self.serial.read(len_remaining)
if type(c) == bytes and sys.version_info > (3,):
temp = ""
for i in c:
temp += chr(i)
c = temp

len_read = len(c);
if len_read > 0:
resp += c
len_remaining -= len_read
if len_found is False and len(resp) >= 5:
if not (ord(resp[1]) & 0x80):
len_remaining = (ord(resp[2]) + 5) - len(resp)
len_found = True
else:
except_code = ord(resp[2])
else:
raise ModbusClientTimeout('Response timeout')
len_read = len(c);
if len_read > 0:
resp += c
len_remaining -= len_read
if len_found is False and len(resp) >= 5:
if not (ord(resp[1]) & 0x80):
len_remaining = (ord(resp[2]) + 5) - len(resp)
len_found = True
else:
except_code = ord(resp[2])
else:
raise ModbusClientTimeout('Response timeout')
finally:
self.last_receive_completion = deadtime_clock()

if trace_func:
s = '%s:%s[addr=%s] <--' % (self.name, str(slave_id), addr)
Expand Down Expand Up @@ -354,6 +379,11 @@ def _write(self, slave_id, addr, data, trace_func=None):
s += '%02X' % (ord(c))
trace_func(s)

wait_until(
target=self.last_receive_completion + self.deadtime,
clock=deadtime_clock,
)

self.serial.flushInput()
try:
if sys.version_info > (3,):
Expand All @@ -362,25 +392,28 @@ def _write(self, slave_id, addr, data, trace_func=None):
except Exception as e:
raise ModbusClientError('Serial write error: %s' % str(e))

while len_remaining > 0:
c = self.serial.read(len_remaining)
if type(c) == bytes and sys.version_info > (3,):
temp = ""
for i in c:
temp += chr(i)
c = temp
len_read = len(c);
if len_read > 0:
resp += c
len_remaining -= len_read
if len_found is False and len(resp) >= 5:
if not (ord(resp[1]) & 0x80):
len_remaining = 8 - len(resp)
len_found = True
else:
except_code = ord(resp[2])
else:
raise ModbusClientTimeout('Response timeout')
try:
while len_remaining > 0:
c = self.serial.read(len_remaining)
if type(c) == bytes and sys.version_info > (3,):
temp = ""
for i in c:
temp += chr(i)
c = temp
len_read = len(c);
if len_read > 0:
resp += c
len_remaining -= len_read
if len_found is False and len(resp) >= 5:
if not (ord(resp[1]) & 0x80):
len_remaining = 8 - len(resp)
len_found = True
else:
except_code = ord(resp[2])
else:
raise ModbusClientTimeout('Response timeout')
finally:
self.last_receive_completion = deadtime_clock()

if trace_func:
s = '%s:%s[addr=%s] <--' % (self.name, str(slave_id), addr)
Expand Down