errors · bitdewfpga bit, nextpnr

design.sv:2: ERROR [empty-module]: the module blinker (design.sv:2), instantiated as u_blink, has no body (no assign, no always), so yosys kept it as a black box, and nextpnr has no cell of that type to place. Not a size problem. Fix: write the body of blinker, or comment the instance u_blink out until it is written.

ERROR: Unable to place cell 'u_blink', no Bels remaining of type 'blinker'
design.sv:2: ERROR [empty-module]: the module blinker (design.sv:2), instantiated as u_blink, has no body (no assign, no always), so yosys kept it as a black box, and nextpnr has no cell of that type to place. Not a size problem. Fix: write the body of blinker, or comment the instance u_blink out until it is written. https://nosey-dewdrop.github.io/dewfpga/errors/empty-module/

Why does it happen?

A module skeleton written first, its body later: yosys treats a module with no logic as a black box (a cell to be supplied elsewhere), and place and route finds nothing to supply it.

What is the fix?

Write the body, or comment the instance out until then.

// blinker u_blink(.clk(clk), .led(led[0]));

Which command prints it?

• dewfpga bit

Which probes in test/sv print this code?

• a submodule declared with its ports and no body (a lab part not written yet), its output used by top

Every probe, with what Vivado does and what each stage does here: the probes, stage by stage.