Nexys4 Pmod 1.8Volt output?

[skyberrys]

Hello, 

I need to output a logic high signal of 1.8V through the pmod connectors on the Nexys4 Board. Right now I have set up my constraints file (.xdc) to LVCMOS18 as the IOSTANDARD, but still when I measure the output on the pmod pin the logic high signal is 3.3V instead of 1.8V.

set_property PACKAGE_PIN B13 [get_ports {jd[0]}]                    
    set_property IOSTANDARD LVCMOS18 [get_ports {jd[0]}]
    set_property PULLDOWN true [get_ports {jd[0]}]

I have the entire IO bank set to 1.8V and still only 3.3V output.

Is it possible to set the output to 1.8V? The datasheet seemed to indicate 1.8V is within the operating range of the Xilinx 7 series FPGA and the literature online for the Nexys4 states the io is from 1.8-3.3V. 

[Alex]

Hi, based on the Pmod spec http://www.digilentinc.com/Pmods/Digilent-Pmod_ Interface_Specification.pdf, it looks like you can't set the voltage below 3.3V right out of the FPGA. Perhaps, others can clarify with this as well. 

The power pins of the interface provide power from the host to the peripheral. The complete interface requires that the host provide the ability to switch the voltage on the power pins between 5.0V and 3.3V. A reduced functionality subset of the spec. allows the host to provide only 3.3V at the power supply pins, with no ability to switch. On the twelve-pin version of the interface, both power supply pins switch together and always supply the same voltage. These pins may be shorted together at either the host end or the peripheral end. 

 

 

 

 

 

[Commanderfranz]

Alex and skyberrys,

After reading through the Nexys 4 reference manual it doesn't look like the Pmod Connector VDD pin can supply any voltage other that 3.3V

Kaitlyn