pavel-kirienko

/// Stateless, purely combinational sin(x) look-up table. Can be used as the phase-to-amplitude converter of an NCO.
/// It stores 256 9-bit items in a look-up table representing the first quarter of the wave.
/// The input x is expected to be normalized into [0, 1024) that maps to [0, 2 pi).
/// The signed output is normalized into [-511, +511] (sic! -512 not used).
module sine_lookup_1024(
    input wire [9:0] x,
    output wire signed [9:0] out
);
    reg [8:0] entry;  // Not an actual register, just a wire assignable from the always block.
    assign out = x[9] ? -$signed({1'b0, entry}) : $signed({1'b0, entry});  // The MSb represents the half-wave index.

pavel-kirienko

/// A numerically controlled oscillator (NCO) that outputs a sawtooth wave, whose frequency is a function of
/// clk rate and frequency_control_word, and the amplitude spans the range [0, 2**OUTPUT_WIDTH).
/// The output frequency is defined as:
///
///     f_out = (f_clk * frequency_control_word) / (2**PHASE_ACCUMULATOR_WIDTH)
///
/// Solve for frequency_control_word:
///
///     frequency_control_word = ((2**PHASE_ACCUMULATOR_WIDTH) * f_out) / f_clk
///

pavel-kirienko

#include <cassert>
#include <cstdint>
#include <cstdlib>

namespace stack_canary
{

/// Do not use this directly; see the StackCanary definition below.
template <std::size_t n_bytes, std::uint8_t seed = 0xC9>
class StackCanary_Impl final

pavel-kirienko

# This script will disable most of the Windows security-related features.
# It is mostly intended for use in disposable VMs, such as simulation and CI/CD runners.
# Read the source to see what exactly is done.
# Author: Pavel Kirienko <[email protected]>

# Relaunch elevated if needed
$IsAdmin = ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()
           ).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)

if (-not $IsAdmin) {

pavel-kirienko

#!/bin/sh

ln -fs /dev/serial/by-id/usb-*Black*Magic*-if00 .bmp.tmp

# Replace arm-zephyr-eabi-gdb with the correct toolchain prefix.
# Update the end address depending on the SRAM size.
arm-zephyr-eabi-gdb --batch -ex 'tar ext .bmp.tmp' -ex 'mon swdp_scan' -ex 'attach 1' -ex 'dump bin mem ram.bin 0x20000000 0x20008000'

# To read all Cortex-M4 core peripheral registers:
#   mem 0xE000E000 0xE000F000 rw 32  # This is not necessary if "set mem inaccessible-by-default off"

pavel-kirienko

#!/usr/bin/env python3

"""
A simple script for extracting numerical data from plots: load an image and click on it to record point coordinates.
Usage example:

    ./trace_image.py my_plot.jpg

Copyright (C) 2025 Pavel Kirienko <[email protected]>
"""

pavel-kirienko

/// Pseudo-inverse of a matrix. There may be a more efficient solution for square matrices; this is a general one.
/// Tolerance less than epsilon*10 may cause numerical instability.
template <auto R, auto C, typename S>
[[nodiscard]] Eigen::Matrix<S, C, R> pinv(const Eigen::Matrix<S, R, C>& a, const S tolerance = std::numeric_limits<S>::epsilon() * 10)
{
    const Eigen::JacobiSVD<Eigen::Matrix<S, R, C>> svd(a, Eigen::ComputeFullU | Eigen::ComputeFullV);
    Eigen::Matrix<S, C, R>                         si;
    si.setZero();
    for (int i = 0; i < svd.singularValues().size(); ++i)
    {

pavel-kirienko

#!/bin/bash
# https://gist.github.com/pavel-kirienko/32e395683e8b7f49e71413aebf5e1a89
# Pavel Kirienko <[email protected]>

HELP="Register slcan-enabled serial-to-CAN adapters as network interfaces.
Usage:
    `basename $0` [options] <tty0> [[options] <tty1> ...]

Interface indexes will be assigned automatically in ascending order, i.e., the
first device will be mapped to slcan0, second to slcan1, and so on.

pavel-kirienko

#!/usr/bin/env python
# Bulk usage:
#   find . -name '*.[ch]pp' -exec bash -c 'recomment.py < "{}" > "{}.out" ; mv "{}.out" "{}"' \;

import sys, re

RE_REPLACE = re.compile(r"(?m)^(\s*?) ?\*(.*)")

def replace_one(match) -> str:
    use_doc = bool(match[1])

pavel-kirienko

# Capture high-frame-rate, high-resolution video of the desktop using ffmpeg.
# The key options are: -c:v libx264 -f flv -vb 1000M -deadline realtime -cpu-used 12
# Without these, the output video peaks at ~5 fps or so.

ffmpeg -video_size 3840x2080 -f x11grab -i :0.0+3840,0 -c:v libx264 -f flv -vb 1000M -deadline realtime -cpu-used 12 output.mp4 -y