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Use calculated delays

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Some serial drivers don't handle draining the transmit buffer
correctly. This has been handled with a long delay so far, which might
be problematic. There's a race condition with some protocol versions.

Until STC15, the baud rate switch is initiated with a command sent by
stcgal, which is replied to by the MCU with the new baud rate. So the
switch of the baud rate has to be done after the command has finished
transmission, but before the MCU has started to transmit the response.

This change calculates the minimum delay needed (with some tolerance
added) so that it's unlikely that the baud rate switch will happen
too late.
This commit is contained in:
Grigori Goronzy 2017-10-10 22:11:07 +02:00
parent ebcfeb467c
commit 68d19f7b88
1 changed files with 21 additions and 9 deletions
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30
stcgal/protocols.py
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@ -238,6 +238,20 @@ class StcBaseProtocol:
return iap_wait
def delay_safely_written(self, length):
"""
Delay until data has been safely written and sent to device.
Some buggy serial drivers don't implement tcdrain/flush correctly.
That is, they wait until all data has been written to USB, but they
do not wait until the data has actually finished transmission.
Add additional delay to work around.
"""
bit_time = 1.0 / self.ser.baudrate
byte_time = bit_time * 11.0 # start, 8 data bits, stop, parity
clock_safety_factor = 1.05 # additional delay in case clock is slow
time.sleep(byte_time * length * clock_safety_factor)
def set_option(self, name, value):
self.options.set_option(name, value)
@ -448,7 +462,7 @@ class Stc89Protocol(StcBaseProtocol):
packet += struct.pack(">H", brt)
packet += bytes([0xff - (brt >> 8), brt_csum, delay, iap])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
self.ser.baudrate = self.baud_handshake
@ -462,7 +476,7 @@ class Stc89Protocol(StcBaseProtocol):
packet += struct.pack(">H", brt)
packet += bytes([0xff - (brt >> 8), brt_csum, delay])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
if response[0] != 0x8e:
@ -638,7 +652,7 @@ class Stc12AProtocol(Stc12AOptionsMixIn, Stc89Protocol):
sys.stdout.flush()
packet = bytes([0x8f, 0xc0, brt, 0x3f, brt_csum, delay, iap])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
self.ser.baudrate = self.baud_handshake
@ -650,7 +664,7 @@ class Stc12AProtocol(Stc12AOptionsMixIn, Stc89Protocol):
sys.stdout.flush()
packet = bytes([0x8e, 0xc0, brt, 0x3f, brt_csum, delay])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
if response[0] != 0x8e:
@ -835,7 +849,7 @@ class Stc12BaseProtocol(StcBaseProtocol):
sys.stdout.flush()
packet = bytes([0x8f, 0xc0, brt, 0x3f, brt_csum, delay, iap])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
self.ser.baudrate = self.baud_handshake
@ -847,7 +861,7 @@ class Stc12BaseProtocol(StcBaseProtocol):
sys.stdout.flush()
packet = bytes([0x8e, 0xc0, brt, 0x3f, brt_csum, delay])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
if response[0] != 0x84:
@ -1121,7 +1135,7 @@ class Stc15AProtocol(Stc12Protocol):
packet += struct.pack(">B", 230400 // self.baud_transfer)
packet += bytes([0xa1, 0x64, 0xb8, 0x00, iap_wait, 0x20, 0xff, 0x00])
self.write_packet(packet)
time.sleep(0.2)
self.delay_safely_written(len(packet))
self.ser.baudrate = self.baud_transfer
response = self.read_packet()
if response[0] != 0x84:
@ -1307,7 +1321,6 @@ class Stc15Protocol(Stc15AProtocol):
response = self.read_packet()
if response[0] != 0x01:
raise StcProtocolException("incorrect magic in handshake packet")
time.sleep(0.2)
self.ser.baudrate = self.baud_transfer
def switch_baud_ext(self):
@ -1324,7 +1337,6 @@ class Stc15Protocol(Stc15AProtocol):
response = self.read_packet()
if response[0] != 0x01:
raise StcProtocolException("incorrect magic in handshake packet")
time.sleep(0.2)
self.ser.baudrate = self.baud_transfer
# for switching back to RC, program factory values