doof.me.uk

Xcowsay fans rejoice! Xcowsay is now officially supported on the Raspberry Pi!

In other news I’ve started updating xcowsay to use Gtk3 and Cario. Expect version 1.4 later in the year!

I thought managing over two years without washing machine malfunction was too good to be true. And lo it was. This time a mysterious banging noise was caused by these as yet unidentified components:

Foolishly I forgot to ask the engineer what the problem was so washing machine lore has not grown. I’m pretty sure they’re not the infamous Carbon Brushes anyway. Answers on a postcard…

For reasons vaguely connected with my day job I found myself at a soiree at a certain marketing suite on the Olympic Park last Thursday. The less said about the event itself the better but I did manage to get a look at the nearly finished venues:

Photo sucks as I only had my phone with me. I suspect this is the closest I’ll be getting to the Olympics this year.

A small nugget of information that might be useful to someone:

The standard timestamps in struct stat have type time_t which only gives a resolution of seconds which is less than required in many situations. Luckily most operating systems provide a higher resolution timestamp within struct stat but the field name differs among Linux, BSD, etc. On Linux you can get at this with st_mtim.tv_nsec and on BSD it is st_mtimespec.tv_nsec (this also works for OS X).

With autoconf you can use something like:

AC_CHECK_MEMBERS([struct stat.st_mtimespec.tv_nsec])
AC_CHECK_MEMBERS([struct stat.st_mtim.tv_nsec])

And then later you can pull the nanoseconds out of the timestamp with:

#if defined HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC
   ns = st.st_mtimespec.tv_nsec;
#elif defined HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
   ns = st.st_mtim.tv_nsec;
#else
   ns = 0;
#endif

This works the same way for atime and ctime as well as mtime. Make sure to handle the #else case as some systems (Cygwin?) don’t have this at all.

A while ago I posted about a VHDL compiler I’d started writing. Well I’ve been working on it a bit during the evenings and weekends and it’s acquired several new features. Probably the most significant is that it can now compile the standard IEEE std_logic_1164 and numeric_std packages as well the Synopsys std_logic_arith and std_logic_unsigned packages. If you clone the latest version from GitHub these will be built and installed for you automatically. Note that the original IEEE sources cannot be redistributed due to copyright restrictions so you’ll have to faff about downloading them from the IEEE standards website first – see lib/ieee/README for details.

NVC also now supports a wider range of concurrent statements, including selected and conditional assignments.

This means we can rewrite the counter example from before in a more normal way:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
entity counter is
    generic ( WIDTH : integer );
    port (
        clk   : in std_logic;
        reset : in std_logic;
        count : out unsigned(WIDTH - 1 downto 0) );
end entity;
 
architecture rtl of counter is
    signal count_r : unsigned(WIDTH - 1 downto 0);
begin
    count <= count_r;
 
    process (clk) is
    begin
        if rising_edge(clk) then
            if reset = '1' then
                count_r <= (others => '0');
            else
                count_r <= count_r + 1;
            end if;
        end if;            
    end process;
end architecture;

And similarly for the top-level test bench:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
entity counter_tb is end entity;
 
architecture test of counter_tb is
    constant WIDTH : integer := 16;
    signal clk     : std_logic := '0';
    signal reset   : std_logic := '1';
    signal count   : unsigned(WIDTH - 1 downto 0);
begin
    clk   <= not clk after 5 ns;
    reset <= '0' after 10 ns;
 
    uut: entity work.counter
        generic map ( WIDTH )
        port map ( clk, reset, count );    
end architecture;

Next we have to analyse and elaborate the design:

$ nvc -a counter.vhd
$ nvc -e counter_tb
/usr/lib/llvm-3.0/bin/llvm-ld -r -b /home/nick/nvc/build/work/_WORK.COUNTER_TB.final.bc /home/nick/nvc/build/work/_WORK.COUNTER_TB.elab.bc /home/nick/share/nvc/ieee/_IEEE.NUMERIC_STD-body.bc /home/nick/share/nvc/ieee/_IEEE.STD_LOGIC_1164-body.bc

The long llvm-ld line at the end is a new stage that links together the LLVM bitcode for the elaborated design with the bitcode for any referenced packages – the IEEE standard libraries in this case. This allows LLVM’s link time optimisation to optimise across package boundaries. For example, inlining trivial functions like rising_edge directly into the process.

$ nvc -r --stop-time=1ms --stats counter_tb
** Note: setup:28ms run:104ms maxrss:17872kB

LLVM JIT compilation accounts for most of the memory usage and 28ms setup time. However this overhead should be insignificant for any long-running simulation.

Just running the above simulation is fairly boring so I’ve also started adding a basic VCD dumper. This only works for a small set of data types but includes std_logic and std_logic_vector so should hopefully be quite useful in practice.

$ nvc -r --stop-time=100ns --vcd=out.vcd counter_tb

The output can then be opened in a VCD viewer such as GTKWave.

Note that writing out a VCD will slow the simulation considerably. In the future I’d like to be able to selectively dump signals and support other formats such as GHW or LXT2.

I went to Munich for a few days last week with my friend Kelly. Mostly it rained so thankfully there were plenty of indoor museums to do. But on the one sunny day we went to this awesome castle at Neuschwanstein in the Alps.

Unfortunately one whole side of the castle was covered in scaffolding but thankfully not the side with the “classic” view:

There’s a few more photos here.

Yesterday while I was out exploring I discovered this beautiful pink tree. Is it a cherry blossom? Maybe a tree scientist would know. Anyway, the tree was full of bees! Which is a bit of rarity these days I think. Tried to take some photos of them but unfortunately they don’t much like posing. Also some pigs for good measure.

Some genius from the intertubes has invented a recipe for bacon milkshake!!! Me and friend Winni made some yesterday and it is tasty meaty goodness. Here are some action shots to go along with the recipe.

First step: fry the bacon! Bacon is the most important ingredient. We used one whole pack.

Put the ice cream and banana in a blender. Banana is to make it look healthy.

Put some bacon and milk into the blender. Probably need quite a bit of milk or it gets too thick. Some syrupy stuff is added around here too.

Blend into bacon paste!!!

Add the rest of the bacon and some cow bisquits. Then blend it all together again. Recipe suggests adding bacon fat here but we skipped that.

Tada! The finished elixir! Filled with nutritious protein. Mmm.

I’m so excited about Eurovision this year. Not only will it be hosted in the glorious nation of Azerbaijan, but our entry will be veteran crooner Engelbert Humperdinck! This could only be improved by him singing his classic hit Lesbian Seagull.

…oh wait, it just got better.

Just received a 32GB SanDisk microSD from Amazon for just twenty cash monies. Bargain! Stock up before someone notices. Still not as big as a coal lump though.