Modifying Arty A7 board for PMOD 1.8V I/O

[swc2]

Hello,

Is there any way to easily modify Arty A7 board such that I can change PMOD I/O voltage from 3.3V  to 1.8V?

Board schematic looks like there are no jumpers between main 3.3V supply line and Artix-7 FPGA bank 14/15 VDD, so that the PMOD I/O voltage is fixed to 3.3V.

I was think to completely disconnect the 3.3V DC/DC converter output on the board and hook up a wire into it to externally supply 1.8V, but wanted to ask if this may work or if there is an easy fix.

In case if there is no easy fix, is there an alternative FPGA board from digilent that supports 1.8V I/O?

Your advice will be much appreciated. 

Thanks,

SW

[xc6lx45]

Hi,

just having a quick look at the Arty schematic, there are for example a current sense monitors on the 3.3 V line (IC15, IC16), the regulator for the XADC (IC14), the 100 MHz oscillator and, most importantly, the flash memory (which usually exists in a 3.3 V and a 1.8 V variant). So I guess the answer is mostly "no", unless you fix a few things (among them probably the FTDI chip IO, which may be impossible).

The 1.8 V supply topic is one I know only too well... The one Digilent board I'm aware of with variable IO voltage is FMC carrier S6. It's not exactly cheap with the FMC IO expander but I've used that one successfully. Also comes with an xc6lx45 component, where have I seen that name ? I'm sure there are others but most likely not the compact / cheap ones.

My "go-to" board would be Trenz TE0725, still semi-breadboard-ish (hint, you can grab 1.8 V from one of the on-board regulators. Attach a wire to the large 1.8 V supply capacitor and route it to one bank's VIO pin). The modules with high density connectors usually require external VIO anyway so you are free to choose.

Another candidate is Lattice ICE40-HX8K, they have 0 ohms resistors in the bank supplies.

 

 

 

 

[zygot]

2 hours ago, xc6lx45 said:

The one Digilent board I'm aware of with variable IO voltage is FMC carrier S6.

The Nexys Video and Genesys2 boards have truly user selectable Vadj. bank Vccio voltages though the only GPIO available are connected to the FMC connector. The FMC carrier S6 is, as far as I know, no longer available for purchase, for a number of very good reasons. I had two at one time. Both self-immolated in spectacular fashion blowing a hole in a corner of the FPGA device.  But I do concur with the advice to find a board that suits your needs rather than try and modify one that doesn't. A good general rule is that if you need to ask for advice as to whether or not you can modify a board the answer is NO. Even if you have the knowledge to analyze the circuit design and figure out a way to change it you still need to have the skill and equipment to do reliable PCB re-work.