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Basys3 PMod voltage output



I start learning about FPGA some days ago but I have a problem with the "PMod". I want to simple turn an Arduino on/off, direct from the VIN (this support 3.3V) using a Basys 3, using the PMod connector. For simplicity I replace the Arduino for one led, for test propose.

When I connect the Arduino into the 3.3V + GND on FPGA the Arduino (and the led) work very well, as expected. However, when change the wire from “3.3V” to another port (K17 for instance) this fail.

The light of the led is weak and the Arduino not turn on. I not have a multimeter to see what is the voltage or more information about what is happening.


I think the pin (JC1, JC2…) is not working on 3.3V, however this is set to use LVCMOS33.


How I can fix that have another way to achieve that?

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This is my first try. I need a way to turn on/off one external device (in this case a Arduino, but I test with one LED) using the FPGA, so no matter what PIN is, only need a 3.3V.

When I saw the PMod I thought that all PINs are 3.3V output. In my mind, probably wrong, I can take any one (JC1/K17 of example) to connect into the VIN of the Arduino. But in reality this is under 3.3V, so I can't power up. When I tested it with a LED the light weaker than the JC6. So probaby the JC1 voltage is less than 3.3V.

Edited by Inkeliz
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The problem is most likely that the regular output pins can't deliver a high enough current to power the Arduino.

"Copied from Basys2 post"
First, the max output current varies depending on how the FPGA is configured. It can be configured to support a max of 16 mA output current.

I am pretty sure the same thing applies to the Basys3 as it does to most microcontrollers.
You should consider using the FPGA only to switch a power supply rail on and off.
There is plenty of posts on the internet how to do this, including this for example.

Good luck

PS: note that these I/O pins have a 200 ohm resistor in series. This will reduce the voltage on these I/O pins as you increase the current.

Edited by StudentAmsterdam
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