failed to place HFOSC

[olegendo]

Hi,

I'm trying to build some simple test logic for the smaller iCE40 devices that uses the built-in oscillator and I'm getting

fatal error: failed to place HFOSC

for "-d 384 -P qn32" and "-d 1k -P qn84". It's OK for "-d 5k -P sg48" though.

Am I missing something?

Cheers, Oleg

Reproducer verilog:

module top (output clkout);

wire clk;

SB_HFOSC #(.CLKHF_DIV("0b10")) hfosc (
  .CLKHFPU(1'b1),
  .CLKHFEN(1'b1),
  .CLKHF(clk)
);

reg [7:0] counter;

always @(posedge clk) begin
  counter <= counter + 1;
end

assign clkout = counter[7];
endmodule

[daveshah1]

There is no built-in oscillator in those devices. The only supported device with an internal oscillator is the UltraPlus 5k.

[olegendo]

According to official documentation ...

The iCE40TM family, specifically iCE40 UltraTM, iCE40 UltraLiteTM and iCE40 UltraPlusTM, features two on-chip oscillators. [...] Two oscillators are available to users: • SB_LFOSC – Low Frequency Oscillator • SB_HFOSC – High Frequency Oscillator with output divider

Or do you mean, it's just not supported by YosysHQ/arachne-pnr tools (yet)?

[daveshah1]

Neither the Ultra nor the UltraLite are supported at all by the tools. The 1k and 384 refer to LP/HX series ice40s

[olegendo]

Ouch. I totally confused all the iCE40 variants. Thanks for the clarification and sorry for the noise.

[mithro]

@olegendo - @awygle has been looking into support for the Ultra and UltraLite devices if I understand?

[olegendo]

It'd be certainly great if there was support for Ultra and UltraLite. iCE5LP1K-SG48ITR looks like an appealing device for some designs.

In my particular case here, it doesn't matter though. I totally goofed it. I was expecting HFOSC to work on an iCE40-LP384-SG32, because I didn't realize that there is this significant difference between LP/HX, Ultra, UltraLite, UltraPlus ... it'd be helpful if they just put everything on one website, not on 3, and did not scatter the information across a bazillion of documents ... oh well :)

[kernelcolton]

So how does one program the ultralight if you can't use yosys? is there another toolchain somewhere?

[olegendo]

AFAIK support for iCE5 devices has been added to yosys and nextpnr upstream not long ago.

[daveshah1]

Support for iCE5 (iCE40 Ultra) devices is in Yosys and nextpnr, and I believe this includes the internal oscillators. There is no support for the iCE40 UltraLite yet.