Correct DC50 enum: 2 -> 50

[thennen]

PS6000a range changed the enum for DC50 coupling from 2 to 50.

[hmaarrfk]

is this true for all firmware versions? for all library versions? maybe we need to condition on the version of the library itself before making this change.

[thennen]

Good question. Hard to know for sure without trying it out on every old dll/firmware. I certainly wouldn't expect them to change the enum between versions. Do you know of any other instances of that happening?

I contacted support and they didn't know either. But they are checking it out.

You can see the information in Pico Technology\SDK\inc\ directory:

in PicoDeviceEnums.h (used by ps6000aApi.h):

typedef enum enPicoCoupling
{
  PICO_AC = 0,
  PICO_DC = 1,

  PICO_DC_50OHM = 50
} PICO_COUPLING;

vs. ps6000Api.h

typedef enum enPS6000Coupling
{
  PS6000_AC,
  PS6000_DC_1M,
  PS6000_DC_50R
} PS6000_COUPLING;

[hmaarrfk]

maybe this is why i broke my scope like 10 years ago..

[thennen]

Well, AndrewA at picoscope support confirmed: "PICO_DC_50OHM enum values were never changed"

So, I think it's safe to merge.

[hmaarrfk]

so which one is the correct value? 2 or 50?

[thennen]

For reference, here is the error I ran into that is fixed by this change.

In [4]: print(ps.getAllUnitInfo())
DriverVersion                 : ps6000a Windows Driver, 1.0.116.3546
USBVersion                    : 3.0
HardwareVersion               : 1.3
VariantInfo                   : 6426E
BatchAndSerial                : JY198/0032
CalDate                       : 07Jun23
KernelVersion                 : 1.0
DigitalHardwareVersion        : 1
AnalogueHardwareVersion       : 3
PicoFirmwareVersion1          : 1.7.16.0
PicoFirmwareVersion2          : 1.1.4.0

In [5]: ps.CHANNEL_COUPLINGS['DC50'] = 2
In [6]: ps.setChannel('A', 'DC50')
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
Cell In[6], line 1
----> 1 ps.ps.setChannel('A', 'DC50')

File ~\Anaconda3\lib\site-packages\picoscope-0.7.20+3.gce48c63-py3.8.egg\picoscope\picobase.py:296, in _PicoscopeBase.setChannel(self, channel, coupling, VRange, VOffset, enabled, BWLimited, probeAttenuation)
    292     # 20kHz Bandwidth Limiter for PicoScope 4444
    293 else:
    294     BWLimited = 0
--> 296 self._lowLevelSetChannel(chNum, enabled, coupling,
    297                          VRangeAPI["apivalue"],
    298                          VOffset / probeAttenuation, BWLimited)
    300 # if all was successful, save the parameters
    301 self.CHRange[chNum] = VRange

File ~\Anaconda3\lib\site-packages\picoscope-0.7.20+3.gce48c63-py3.8.egg\picoscope\ps6000a.py:461, in PS6000a._lowLevelSetChannel(self, chNum, enabled, coupling, VRange, VOffset, BWLimited)
    458 else:
    459     m = self.lib.ps6000aSetChannelOff(c_int16(self.handle),
    460                                       c_enum(chNum))
--> 461 self.checkResult(m)

File ~\Anaconda3\lib\site-packages\picoscope-0.7.20+3.gce48c63-py3.8.egg\picoscope\picobase.py:1153, in _PicoscopeBase.checkResult(self, errorCode)
   1151 ecName = self.errorNumToName(errorCode)
   1152 ecDesc = self.errorNumToDesc(errorCode)
-> 1153 raise IOError('Error calling %s: %s (%s)' % (
   1154     str(inspect.stack()[1][3]), ecName, ecDesc))

OSError: Error calling _lowLevelSetChannel: PICO_INVALID_COUPLING (An invalid coupling type was specified in psXXXXSetChannel.)

In [7]: ps.CHANNEL_COUPLINGS['DC50'] = 50
In [8]: ps.setChannel('A', 'DC50')
Out[8]: 2.0

[thennen]

so which one is the correct value? 2 or 50?

50

[hmaarrfk]

What is the meaning of the return value of 2.0 in:

In [7]: ps.CHANNEL_COUPLINGS['DC50'] = 50
In [8]: ps.setChannel('A', 'DC50')
Out[8]: 2.0

[thennen]

That is the "Actual range of the scope as double" returned by _PicoscopeBase.setChannel.

in this case, 2.0 is the default value.

https://github.com/colinoflynn/pico-python/blob/1747100291d2c3d86eee17e90de0abc633f947e6/picoscope/picobase.py#L306C11-L306C11

[hmaarrfk]

I see. can you add a release note

[hmaarrfk]

oh we have no release notes lol

[BenediktBurger]

Thanks for that fix. I encountered the error as well, but did not investigate further, as I did not need it.

When I created the ps6000a file, I took the enum from ps4000a (and there the value is 2) as I expected them to have the same enum values...

Finally it is solved, thanks a lot @thennen!

[hmaarrfk]

amazing. thank you for the confirmation that this works!!!