I am very new to Alchitry, and was looking for some assistance in how to use the Br component. I want to use the Br’s pins to turn on the LEDs (the LED pins in bank D according to the pinout reference). How would I do this? I think I have to add .xdc constraints, but the file is read only? Please help, or show me some of your own projects with the Br!
You mean turn the LEDs on via external hardware connected through the Br board, instead of controlling them through the FPGA itself? You should only have to do two things:
- change the led ports in your au_top module to be input instead of output. If you leave them as output, they will drive against your external drivers of the lines and they will fight.
- wire up your external connections to the Br lines marked as connected to the LEDs, and either leave them low, or drive them high with 3.3V.
I’m not sure if the way the LEDs are implemented on the Au, whether you would need pulldowns or not. It also might depend on what you’re doing the external driving with.
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Assuming you’re using Alchitry Labs, you define pinouts with Alchitry Constraint files.
This is the easiest way to define connections. The LEDs are simply LEDx.
If you’re trying to drive the LEDs without the FPGA through the Br, you can do that as long as you make the FPGA pin an input or write bx to them so you’re not fighting the output.
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