better doc string

1 files changed, 22 insertions, 1 deletions

diff --git a/qolab/hardware/scope/rigolds1054z.py b/qolab/hardware/scope/rigolds1054z.py
index a97db67..8a7d9a5 100644
--- a/qolab/hardware/scope/rigolds1054z.py
+++ b/qolab/hardware/scope/rigolds1054z.py
@@ -171,7 +171,7 @@ class RigolDS1054z(ScopeSCPI):
         chunk_size = 70_000  # unfortunately large chunk size prone to read errors
         errCnt = 0
         strt = 1
-        stp = min(maxreadable, Npnts)
+        stp = min(chunk_size, Npnts)
         errorFreeChunkSize = []
         errorProneChunkSize = []
         while strt <= Npnts:
@@ -182,6 +182,17 @@ class RigolDS1054z(ScopeSCPI):
             self.write(f":WAVeform:STOP {stp}")
             qstr = ":WAVeform:DATA?"
             try:
+                """
+                All this caraziness with tuning chunk_size
+                is because Rigol usbtmc connection is bugy.
+                It present itself as high speed device over USB,
+                but set incompatible packet size of 64
+                while the USB standard dictates 512.
+                In linux dmesg complains:
+                kernel: ... bulk endpoint 0x3 has invalid maxpacket 64
+
+                Seel
+
                 wfRawChunk = self.query_binary_values(
                     qstr,
                     datatype="b",
@@ -192,6 +203,16 @@ class RigolDS1054z(ScopeSCPI):
                 if len(wfRawChunk) == 0:
                     continue  # we need to repeat chunk read
                 wfRaw[strt - 1 : stp] = wfRawChunk
+                """
+                All this craziness with tuning chunk_size
+                and catching VisaIOError
+                is because Rigol usbtmc connection is bugy.
+                It present itself as high speed device over USB,
+                but set incompatible packet size of 64
+                while the USB standard dictates 512.
+                In linux dmesg complains:
+                'bulk endpoint 0x3 has invalid maxpacket 64'
+                """
                 errorFreeChunkSize.append(chunk_size)
                 chunk_size = min(maxreadable, int(chunk_size * 1.1))
                 strt += chunk_size