Mixed HDL on Fomu¶

Hint

It is strongly suggested to get familiar with Verilog on Fomu and VHDL on Fomu examples before tinkering with these mixed language use cases.

“Hello world!” - Blink a LED¶

The canonical “Hello, world!” of hardware is to blink a LED. The directory hdl/mixed/blink contains a VHDL + Verilog example of a blink project. This takes the 48 MHz clock and divides it down by a large number so you get an on/off pattern.

Enter the hdl/mixed/blink directory and build the demo by using make:

make FOMU_REV=$FOMU_REV

You can then load blink.dfu onto Fomu by using make load or the same dfu-util -D command we’ve been using so far. You should see a blinking pattern of varying color on your Fomu, indicating your bitstream was successfully loaded.

If you take a closer look at the sources in hdl/mixed/blink, you will find that modules/components blink and clkgen are written both in VHDL and Verilog. The Makefile uses blink.vhd and clkgen.v by default. However, any of the following cases produce the same result:

blink.vhd + clkgen.v
blink.v + clkgen.vhdl
blink.vhd + clkgen.vhdl
blink.v + clkgen.v

You can modify variables VHDL_SYN_FILES and VERILOG_SYN_FILES in the Makefile for trying other combinations. For a better understanding, it is suggested to compare these modules with the single file solutions in Verilog on Fomu and VHDL on Fomu.