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Implement some details of USBTMC specification - helps to recover from read timeout #50

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Implement some details of USBTMC specification - helps to recover from read timeout #50

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e52b91e
Read Bulk-IN data during abort_bulk_in sequence
Jan 9, 2019
3ae28c5
Clear Bulk-OUT endpoint after abort_bulk_out
Jan 9, 2019
15343d4
Ignore EOM flag when device sends partial data
Jan 9, 2019
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47 changes: 39 additions & 8 deletions usbtmc/usbtmc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -264,6 +264,11 @@ def __init__(self, *args, **kwargs):

self.timeout = 5.0

# Separate timeout for abort sequences. It is reasonable to wait
# longer during an abort sequence, to avoid leaving the device
# in an unusable state.
self.abort_timeout = 5.0

self.bulk_in_ep = None
self.bulk_out_ep = None
self.interrupt_in_ep = None
Expand Down Expand Up @@ -704,7 +709,14 @@ def read_raw(self, num=-1):
else:
eom = False
else:
eom = transfer_attributes & 1
# Only consider EOM flag when transfer_size bytes received.
# See USBTMC v1.00 3.3.1.1:
# "The host must ignore EOM if the device does not
# send TransferSize message data bytes."
if len(data) >= transfer_size:
eom = (transfer_attributes & 1) != 0
else:
eom = False
read_data += data

# Advantest devices never signal EOI and may only send one read packet
Expand Down Expand Up @@ -869,14 +881,16 @@ def _abort_bulk_out(self, btag=None):
if btag is None:
btag = self.last_btag

abort_timeout_ms = int(1000 * self.abort_timeout)

# Send INITIATE_ABORT_BULK_OUT
b = self.device.ctrl_transfer(
bmRequestType=usb.util.build_request_type(usb.util.CTRL_IN, usb.util.CTRL_TYPE_CLASS, usb.util.CTRL_RECIPIENT_ENDPOINT),
bRequest=USBTMC_REQUEST_INITIATE_ABORT_BULK_OUT,
wValue=btag,
wIndex=self.bulk_out_ep.bEndpointAddress,
data_or_wLength=0x0002,
timeout=self._timeout_ms
timeout=abort_timeout_ms
)
if (b[0] == USBTMC_STATUS_SUCCESS):
# Initiate abort bulk out succeeded, wait for completion
Expand All @@ -888,14 +902,17 @@ def _abort_bulk_out(self, btag=None):
wValue=0x0000,
wIndex=self.bulk_out_ep.bEndpointAddress,
data_or_wLength=0x0008,
timeout=self._timeout_ms
timeout=abort_timeout_ms
)
time.sleep(0.1)
if (b[0] != USBTMC_STATUS_PENDING):
break
else:
# no transfer in progress; nothing to do
pass
if (b[0] == USBTMC_STATUS_SUCCESS):
# Abort request completed. Clear endpoint.
# See USBTMC v1.00 4.2.1.3:
# "The host must send a CLEAR_FEATURE control endpoint
# request to clear the Bulk-OUT halt."
self.bulk_out_ep.clear_halt()

def _abort_bulk_in(self, btag=None):
"Abort bulk in"
Expand All @@ -906,16 +923,30 @@ def _abort_bulk_in(self, btag=None):
if btag is None:
btag = self.last_btag

abort_timeout_ms = int(1000 * self.abort_timeout)

# Send INITIATE_ABORT_BULK_IN
b = self.device.ctrl_transfer(
bmRequestType=usb.util.build_request_type(usb.util.CTRL_IN, usb.util.CTRL_TYPE_CLASS, usb.util.CTRL_RECIPIENT_ENDPOINT),
bRequest=USBTMC_REQUEST_INITIATE_ABORT_BULK_IN,
wValue=btag,
wIndex=self.bulk_in_ep.bEndpointAddress,
data_or_wLength=0x0002,
timeout=self._timeout_ms
timeout=abort_timeout_ms
)

if (b[0] == USBTMC_STATUS_SUCCESS):
# Read remaining data from bulk in endpoint.
# This is a required step before the abort request can complete.
#
# See USBTMC v1.00 4.2.1.4:
# "The host should continue reading from the Bulk-IN endpoint
# until a short packet is received."
# USBTMC v1.00 4.2.1.5:
# "The host should not send CHECK_ABORT_BULK_IN_STATUS until
# a short Bulk-IN packet has been received."
resp = self.bulk_in_ep.read(self.max_transfer_size, timeout=abort_timeout_ms)

# Initiate abort bulk in succeeded, wait for completion
while True:
# Check status
Expand All @@ -925,7 +956,7 @@ def _abort_bulk_in(self, btag=None):
wValue=0x0000,
wIndex=self.bulk_in_ep.bEndpointAddress,
data_or_wLength=0x0008,
timeout=self._timeout_ms
timeout=abort_timeout_ms
)
time.sleep(0.1)
if (b[0] != USBTMC_STATUS_PENDING):
Expand Down