Is there an SDK interface for the DigitalIn voltage thresholds?

[Pseudonym1]

In the Device manager for the AD2, there's an option for 1V8 Digital inputs. Is there an SDK function equivalent to set/get this, or otherwise adjust to the 1V8 range?

Are there specifications on the voltage thresholds (and any other parameters such as setup & hold timing) for both settings?

Does using the 1.8V setting impact the 5V tolerance of the pins, or the pin current if > VIO > 3.3V?

-Thanks

[attila]

Hi @Pseudonym1

On AD1-2 the 5th device configuration provides ~0.6V digital input logic threshold suitable for 1.2-1.8V signals.
FDwfDeviceConfigOpen(int idxDev, int idxCfg = 4, HDWF *phdwf) // 4 = 5th

For further details see the following post:

 

[Pseudonym1]

Is there any chance there are specs for the VIH and VIL voltage levels in this 1.8V and the 3.3V input mode?

It's implied that the pins are still 3.3V tolerant (since some could be setup as outputs), but can you confirm?

-Thanks

[attila]

Hi @Pseudonym1

The high level digital output of Analog Discovery 1&2 and Electronics Explorer is 3.3V, only the input threshold can be changed from 1.5V to 0.5V with the 5th and 7th configurations.

You can find the specifications in the following document, see LVCMOS33 and LVCMOS18: https://www.xilinx.com/support/documentation/data_sheets/ds162.pdf

Here you can see the 1.5V threshold in action:

and the 0.5V threshold with 5th device configuration:

[Pseudonym1]

Thanks for the information @attila

What is this 7th configuration? Are the configurations documented somewhere other than the waveform GUI?

[JColvin]

Hi @Pseudonym1,

I think the 7th configuration is for the Electronics Explorer board. The Analog Discovery 2 (as you noted) does not have a 7th configuration option, but does have the 0.5V threshold option in the 5th configuration.

Thanks,
JColvin

[Pseudonym1]

Thanks for the replies.

I am calling the FDwfDeviceConfigOpen function now, but I'm not sure the call is having an impact. Is there a way to verify the setting? In mode 4 (larger Digital buffers, but no analog buffers) will FDwfAnalogInConfigure still return a meaningful result? It would be great if it does, but seeing it return a value makes me think the mode setting didn't work. I am using the Python interface on Ubuntu 14.04 with DWF Version 3.7.5

[attila]

Hi @Pseudonym1

The 4th configuration, FDwfDeviceConfigOpen( , 3, ), supports digital in, out, io and analog io. Analog in/out are not supported in this configuration.

[Pseudonym1]

Indeed, I had an off by 1 error.

In the 4th mode, FDwfAnalogInStatusSample( ) yields 0 in the voltage parameter for both AD2 Analog In channels.

[attila]

Hi @Pseudonym1

The WF v3.7.13 adds Scope and Wavegen support for 4th configuration of AD 1&2
https://forum.digilentinc.com/topic/8908-waveforms-beta-download/

 

[Pseudonym1]

Great! This tool gets better and better.