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Configure Rising/Falling Edge trigger
Description of issue
Hi, this is regarding this closed issue: https://github.com/ni/nimi-python/issues/902 Here, the reasoning for the removal of configurable Rising/Falling edge trigger functionality is given as: "One piece of functionality we removed is configuring the trigger edge (rising vs falling). We did this after careful consideration because all our SMUs are PXI / PXIe, which per the PXI spec defines triggers going over the trigger bus as rising edge. If this is a problem for your application, we'd love to hear more about it" But all the other NI Modular Instruments' Python API have this functionality available. Moreover, there are ways to configure this using the LabVIEW DCPower API. Could you elaborate on why exactly this reasoning is given? By all accounts, it seems that the PXI bus can handle both rising and falling edge triggers.
In short: we couldn’t come up with a real world use case for it, so decided to err on the side of keeping the API smaller. Negative logic triggering is more commonly used for interfacing with third party instruments outside of PXI via the front panel connectors.
Do you have a need for configuring the triggers on SMUs as falling edge?
Hi, I need this functionality to be able to trigger on the Failing edge. Is there a work around for this?
In short: we couldn’t come up with a real world use case for it, so decided to err on the side of keeping the API smaller. Negative logic triggering is more commonly used for interfacing with third party instruments outside of PXI via the front panel connectors.
Do you have a need for configuring the triggers on SMUs as falling edge?
I really need this functionality. Can you please add it back to the library
I would like to hear about your use case and why you need triggers configure in this manner so that the work can be prioritized ahead of other things.
There is an easy workaround.
You can call _set_attribute_vi_int32(self, attribute_id, attribute_value)(https://github.com/ni/nimi-python/blob/a94b20c47624b4b91e2b7e3befa313c76543c03d/generated/nidcpower/nidcpower/session.py#L6389) directly to configure any attribute.
I attach nidcpower.h header file which has the attribute definitions.
For calculating attribute_id, use 1,150,000 for NIDCPOWER_ATTR_BASE.
For attribute_value use NIDCPOWER_VAL_BASE of 1,000.
I would like to hear about your use case and why you need triggers configure in this manner so that the work can be prioritized ahead of other things.
There is an easy workaround.
You can call
_set_attribute_vi_int32(self, attribute_id, attribute_value)(https://github.com/ni/nimi-python/blob/a94b20c47624b4b91e2b7e3befa313c76543c03d/generated/nidcpower/nidcpower/session.py#L6389
) directly to configure any attribute. I attach
nidcpower.hheader file which has the attribute definitions.For calculating
attribute_id, use 1,150,000 forNIDCPOWER_ATTR_BASE. Forattribute_valueuseNIDCPOWER_VAL_BASEof 1,000.
Thanks for the quick reply, but is the NIDCPOWER_ATTR_BASE and NIDCPOWER_VAL_BASE values common for all SMUs devices?
Hi @marcoskirsch, our user case is to trigger on the falling edge, because that is where the response to the input is taking place. Our DUT measures system changes on the Raising edge while on the Falling edge it applies its response to the system changes.
By the way, is it possible to configure back panel triggers of the chassis to be used for measuring triggers? I have tried to use the back panel for this purpose but it fails while the front panel trigger on the controller works.
Thanks for the quick reply, but is the NIDCPOWER_ATTR_BASE and NIDCPOWER_VAL_BASE values common for all SMUs devices?
Yes, these constants are for the NI-DCPower API regardless of which SMU model you are using.
By the way, is it possible to configure back panel triggers of the chassis to be used for measuring triggers? I have tried to use the back panel for this purpose but it fails while the front panel trigger on the controller works.
To make sure I understand, let me paraphrase what you are asking:
What "back panel triggers of the chassis" are you referring to? What is the model of PXIe chassis that you are using? Some NI chassis have a connector in the back for getting triggers across the PXI Trigger bus from one chassis to another one. But I don't know which specific connectors you are referring to.
NIDCPOWER_VAL_BASE
Hi Marcoskirsch, the advice you gave me last time worked for the PXIe-4141 and now we migrated to the PXIe-4163 SMUs, but now this feature is not working since the migration. I get the error -1074097882: Requested value is not a supported value for this property. Can you help me here.
While the API is common for NI-DCPower, that does not mean that all instruments support all the same configuration options.
In this case, it appears the NI PXIe-4163 SMU does not support the setting you want. Can you tell me, using the C symbol names from nidcpower.h what attribute you are configuring to what value? Maybe a code snippet?
`
self.__smu._set_attribute_vi_int32(
attribute_id=(NIDCPOWER_ATTR_BASE + 35),
attribute_value=(NIDCPOWER_VAL_BASE + 17))
`
bases are `
NIDCPOWER_ATTR_BASE = 1150000
NIDCPOWER_VAL_BASE = 1000
`
After further internal discussion, we determined that this property is not currently supported by any of our newer architecture NI-DCPower devices. Given the complexity and size of the nidcpower API and the fact that the set_attribute workaround is readily available, we've decided not to add this property to our public API.
This is in line with our API Design Guidelines which say "If there's debate on whether a function should be included or not, then don't include it". (Properties, enums, etc aren't mentioned in that line, but they're implied).
If support for the property is added for a new device, we will revisit that decision. If the workaround is untenable to a particular user, please comment to let us know.
