From 7fc0e7e349693ec2594aeeda01f3242cce1c5e42 Mon Sep 17 00:00:00 2001
From: Jimmy van den Bergh <jimmy.vandenbergh@admesy.com>
Date: Thu, 21 Nov 2024 12:54:47 +0100
Subject: [PATCH 1/4] updated to support partial usbtmc message reads from
device to support IEEE 488.2 arbitrary block reads fixes the requested data
to be send in the header instead of recv_chunk.
---
CHANGES | 2 ++
pyvisa_py/protocols/usbtmc.py | 21 ++++++++++-----------
2 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/CHANGES b/CHANGES
index 823fa5a6..2b38adaf 100644
--- a/CHANGES
+++ b/CHANGES
@@ -10,6 +10,8 @@ PyVISA-py Changelog
has been read (see specification), and only expects a header on the first packet received.
- fix usbtmc implementation to properly discard the alignment bytes
ensuring only the actual data (`transfer_size`) is retained in the message PR #465
+- Implemented partial USBTMC message functionality that allows reading the amount of bytes
+ specified by host.
- add support for VI_ATTR_SUPPRESS_END_EN for USB resources PR #449
0.7.2 (07/03/2024)
diff --git a/pyvisa_py/protocols/usbtmc.py b/pyvisa_py/protocols/usbtmc.py
index 8bbac953..6e7b3659 100644
--- a/pyvisa_py/protocols/usbtmc.py
+++ b/pyvisa_py/protocols/usbtmc.py
@@ -455,13 +455,6 @@ def write(self, data):
return size
def read(self, size):
- header_size = 12
- max_padding = 511
- recv_chunk = self.usb_recv_ep.wMaxPacketSize - header_size
-
- if size > 0 and size < recv_chunk:
- recv_chunk = size
-
eom = False
raw_read = super(USBTMC, self).read
@@ -473,12 +466,12 @@ def read(self, size):
received_transfer = bytearray()
self._btag = (self._btag % 255) + 1
- req = BulkInMessage.build_array(self._btag, recv_chunk, None)
+ req = BulkInMessage.build_array(self._btag, size, None)
raw_write(req)
try:
- resp = raw_read(recv_chunk + header_size + max_padding)
+ resp = raw_read(self.usb_recv_ep.wMaxPacketSize)
response = BulkInMessage.from_bytes(resp)
received_transfer.extend(response.data)
while (
@@ -491,15 +484,21 @@ def read(self, size):
# is sent (one whose length is less than wMaxPacketSize)
# wMaxPacketSize may be incorrectly reported by certain drivers.
# Therefore, continue reading until the transfer_size is reached.
- resp = raw_read(recv_chunk + header_size + max_padding)
+ resp = raw_read(self.usb_recv_ep.wMaxPacketSize)
received_transfer.extend(resp)
# Detect EOM only when device sends all expected bytes.
if len(received_transfer) >= response.transfer_size:
eom = response.transfer_attributes & 1
+ if not eom and len(received_transfer) >= size:
+ # Read asking for 'size' bytes from the device.
+ # This may be less then the device wants to send back in a message
+ # Therefore the request does not mean that we must receive a EOM.
+ # Multiple `transfers` will be required to retrieve the remaining bytes.
+ eom = True
# Truncate data to the specified length (discard padding)
# USBTMC header (12 bytes) has already truncated
- received_message.extend(received_transfer[: response.transfer_size])
+ received_message.extend(received_transfer[: response.transfer_size])
except (usb.core.USBError, ValueError):
# Abort failed Bulk-IN operation.
self._abort_bulk_in(self._btag)
From ca8df6c9e0d7b76f3d56c6c1bb125b5fa26a7eab Mon Sep 17 00:00:00 2001
From: Jimmy van den Bergh <jimmy.vandenbergh@admesy.com>
Date: Mon, 2 Dec 2024 11:06:28 +0100
Subject: [PATCH 2/4] Speedoptimazation for read, we now use large chuck sizes.
---
pyvisa_py/protocols/usbtmc.py | 56 +++++++++++++++++++++++++----------
1 file changed, 40 insertions(+), 16 deletions(-)
diff --git a/pyvisa_py/protocols/usbtmc.py b/pyvisa_py/protocols/usbtmc.py
index 6e7b3659..ddcad088 100644
--- a/pyvisa_py/protocols/usbtmc.py
+++ b/pyvisa_py/protocols/usbtmc.py
@@ -12,6 +12,7 @@
"""
import enum
+import math
import struct
import time
import warnings
@@ -455,6 +456,7 @@ def write(self, data):
return size
def read(self, size):
+ usbtmc_header_size = 12
eom = False
raw_read = super(USBTMC, self).read
@@ -467,25 +469,23 @@ def read(self, size):
self._btag = (self._btag % 255) + 1
req = BulkInMessage.build_array(self._btag, size, None)
-
raw_write(req)
try:
- resp = raw_read(self.usb_recv_ep.wMaxPacketSize)
+ # make sure the data request is in multitudes of wMaxPacketSize.
+ # + 1 * wMaxPacketSize for message sizes that equals wMaxPacketSize == size + usbtmc_header_size.
+ # This to be able to retrieve a short package to end communication
+ # (see USB 2.0 Section 5.8.3 and USBTMC Section 3.3)
+ chunck_size = (
+ math.floor(
+ (size + usbtmc_header_size) / self.usb_recv_ep.wMaxPacketSize
+ )
+ + 1
+ ) * self.usb_recv_ep.wMaxPacketSize
+ resp = raw_read(chunck_size)
+
response = BulkInMessage.from_bytes(resp)
received_transfer.extend(response.data)
- while (
- len(resp) == self.usb_recv_ep.wMaxPacketSize
- or len(received_transfer) < response.transfer_size
- ):
- # USBTMC Section 3.3 specifies that the first usb packet
- # must contain the header. the remaining packets do not need
- # the header the message is finished when a "short packet"
- # is sent (one whose length is less than wMaxPacketSize)
- # wMaxPacketSize may be incorrectly reported by certain drivers.
- # Therefore, continue reading until the transfer_size is reached.
- resp = raw_read(self.usb_recv_ep.wMaxPacketSize)
- received_transfer.extend(resp)
# Detect EOM only when device sends all expected bytes.
if len(received_transfer) >= response.transfer_size:
@@ -496,8 +496,32 @@ def read(self, size):
# Therefore the request does not mean that we must receive a EOM.
# Multiple `transfers` will be required to retrieve the remaining bytes.
eom = True
- # Truncate data to the specified length (discard padding)
- # USBTMC header (12 bytes) has already truncated
+ else:
+ while (
+ (len(resp) % self.usb_recv_ep.wMaxPacketSize) == 0
+ or len(received_transfer) < response.transfer_size
+ ) and not eom:
+ # USBTMC Section 3.3 specifies that the first usb packet
+ # must contain the header. the remaining packets do not need
+ # the header the message is finished when a "short packet"
+ # is sent (one whose length is less than wMaxPacketSize)
+ # wMaxPacketSize may be incorrectly reported by certain drivers.
+ # Therefore, continue reading until the transfer_size is reached.
+ chunck_size = (
+ math.floor(
+ (size - len(received_transfer))
+ / self.usb_recv_ep.wMaxPacketSize
+ )
+ + 1
+ ) * self.usb_recv_ep.wMaxPacketSize
+ resp = raw_read(chunck_size)
+ received_transfer.extend(resp)
+ if len(received_transfer) >= response.transfer_size:
+ eom = response.transfer_attributes & 1
+ if not eom and len(received_transfer) >= size:
+ eom = True
+ # Truncate data to the specified length (discard padding)
+ # USBTMC header (12 bytes) has already truncated
received_message.extend(received_transfer[: response.transfer_size])
except (usb.core.USBError, ValueError):
# Abort failed Bulk-IN operation.
From 4286e5647cd95c352e484f42b836869caa056c02 Mon Sep 17 00:00:00 2001
From: Jimmy van den Bergh <93945571+Jimmyvandenbergh@users.noreply.github.com>
Date: Sat, 7 Dec 2024 23:29:58 +0100
Subject: [PATCH 3/4] Fix typo in chunck VS chunk
---
pyvisa_py/protocols/usbtmc.py | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/pyvisa_py/protocols/usbtmc.py b/pyvisa_py/protocols/usbtmc.py
index ddcad088..da0cc888 100644
--- a/pyvisa_py/protocols/usbtmc.py
+++ b/pyvisa_py/protocols/usbtmc.py
@@ -476,13 +476,13 @@ def read(self, size):
# + 1 * wMaxPacketSize for message sizes that equals wMaxPacketSize == size + usbtmc_header_size.
# This to be able to retrieve a short package to end communication
# (see USB 2.0 Section 5.8.3 and USBTMC Section 3.3)
- chunck_size = (
+ chunk_size = (
math.floor(
(size + usbtmc_header_size) / self.usb_recv_ep.wMaxPacketSize
)
+ 1
) * self.usb_recv_ep.wMaxPacketSize
- resp = raw_read(chunck_size)
+ resp = raw_read(chunk_size)
response = BulkInMessage.from_bytes(resp)
received_transfer.extend(response.data)
@@ -507,14 +507,14 @@ def read(self, size):
# is sent (one whose length is less than wMaxPacketSize)
# wMaxPacketSize may be incorrectly reported by certain drivers.
# Therefore, continue reading until the transfer_size is reached.
- chunck_size = (
+ chunk_size = (
math.floor(
(size - len(received_transfer))
/ self.usb_recv_ep.wMaxPacketSize
)
+ 1
) * self.usb_recv_ep.wMaxPacketSize
- resp = raw_read(chunck_size)
+ resp = raw_read(chunk_size)
received_transfer.extend(resp)
if len(received_transfer) >= response.transfer_size:
eom = response.transfer_attributes & 1
From 6a0c720ea44d0bd45620c113051de35a0966023f Mon Sep 17 00:00:00 2001
From: Matthieu Dartiailh <marul@laposte.net>
Date: Tue, 17 Dec 2024 08:50:28 +0100
Subject: [PATCH 4/4] Update release notes
---
CHANGES | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/CHANGES b/CHANGES
index 2b38adaf..91133c39 100644
--- a/CHANGES
+++ b/CHANGES
@@ -11,7 +11,7 @@ PyVISA-py Changelog
- fix usbtmc implementation to properly discard the alignment bytes
ensuring only the actual data (`transfer_size`) is retained in the message PR #465
- Implemented partial USBTMC message functionality that allows reading the amount of bytes
- specified by host.
+ specified by host PR #470
- add support for VI_ATTR_SUPPRESS_END_EN for USB resources PR #449
0.7.2 (07/03/2024)