diff --git a/build_lchm_clock_counter.sh b/build_lchm_clock_counter.sh
new file mode 100755
index 0000000..7210fd8
--- /dev/null
+++ b/build_lchm_clock_counter.sh
@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+CXX="${CXX:-g++}"
+OUT="${OUT:-lchm_clock_counter.exe}"
+
+CXXFLAGS=(
+  -std=c++17
+  -O2
+  -Wall
+  -Wextra
+  -pedantic
+)
+
+SOURCES=(
+  lchm_clock_counter.cpp
+)
+
+LDFLAGS=(
+  -ldl
+)
+
+"$CXX" "${CXXFLAGS[@]}" "${SOURCES[@]}" "${LDFLAGS[@]}" -o "$OUT"
+
+echo "Built $OUT"
diff --git a/lchm_clock_counter.cpp b/lchm_clock_counter.cpp
new file mode 100644
index 0000000..5ac743c
--- /dev/null
+++ b/lchm_clock_counter.cpp
@@ -0,0 +1,883 @@
+#ifdef _WIN32
+    #ifndef NOMINMAX
+        #define NOMINMAX
+    #endif
+    #include <windows.h>
+#else
+    #include <csignal>
+    #include <dlfcn.h>
+#endif
+
+#ifdef _MSC_VER
+    #pragma warning(push)
+    #pragma warning(disable: 4995)
+#endif
+#include "x502api.h"
+#include "e502api.h"
+#ifdef _MSC_VER
+    #pragma warning(pop)
+#endif
+
+#include <algorithm>
+#include <array>
+#include <chrono>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <iomanip>
+#include <iostream>
+#include <limits>
+#include <optional>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <vector>
+
+namespace {
+
+constexpr uint32_t kE502DiSyn2Mask =
+    (static_cast<uint32_t>(1U) << 13U) | (static_cast<uint32_t>(1U) << 17U);
+constexpr uint32_t kE502Digital2Mask = (static_cast<uint32_t>(1U) << 1U);
+
+struct Config {
+    std::string serial;
+    std::optional<uint32_t> ip_addr;
+
+    uint32_t clock_mode = X502_SYNC_DI_SYN1_RISE;
+    double clock_hz = 2000000.0;
+    uint32_t windows = 1000;
+
+    uint32_t recv_block_words = 8192;
+    uint32_t recv_timeout_ms = 50;
+    uint32_t clock_wait_ms = 5000;
+    uint32_t lchm_wait_ms = 5000;
+    uint32_t input_buffer_words = 262144;
+    uint32_t input_step_words = 8192;
+
+    bool pullup_syn1 = false;
+    bool pullup_syn2 = false;
+};
+
+struct LchmClockCount {
+    uint64_t clocks = 0;
+    uint64_t di2_high_clocks = 0;
+    uint64_t di2_low_clocks = 0;
+
+    void clear() {
+        clocks = 0;
+        di2_high_clocks = 0;
+        di2_low_clocks = 0;
+    }
+
+    void add(bool di2_high) {
+        ++clocks;
+        if (di2_high) {
+            ++di2_high_clocks;
+        } else {
+            ++di2_low_clocks;
+        }
+    }
+};
+
+struct RunningStats {
+    uint64_t count = 0;
+    uint64_t clocks_min = std::numeric_limits<uint64_t>::max();
+    uint64_t clocks_max = 0;
+    uint64_t clocks_sum = 0;
+    uint64_t high_min = std::numeric_limits<uint64_t>::max();
+    uint64_t high_max = 0;
+    uint64_t high_sum = 0;
+    uint64_t low_min = std::numeric_limits<uint64_t>::max();
+    uint64_t low_max = 0;
+    uint64_t low_sum = 0;
+
+    void add(const LchmClockCount& value) {
+        ++count;
+        clocks_min = std::min(clocks_min, value.clocks);
+        clocks_max = std::max(clocks_max, value.clocks);
+        clocks_sum += value.clocks;
+        high_min = std::min(high_min, value.di2_high_clocks);
+        high_max = std::max(high_max, value.di2_high_clocks);
+        high_sum += value.di2_high_clocks;
+        low_min = std::min(low_min, value.di2_low_clocks);
+        low_max = std::max(low_max, value.di2_low_clocks);
+        low_sum += value.di2_low_clocks;
+    }
+};
+
+[[noreturn]] void fail(const std::string& message) {
+    throw std::runtime_error(message);
+}
+
+std::string trim_copy(const std::string& text) {
+    const auto first = text.find_first_not_of(" \t\r\n");
+    if (first == std::string::npos) {
+        return {};
+    }
+    const auto last = text.find_last_not_of(" \t\r\n");
+    return text.substr(first, last - first + 1);
+}
+
+bool starts_with(const std::string& value, const std::string& prefix) {
+    return value.rfind(prefix, 0) == 0;
+}
+
+uint32_t parse_u32(const std::string& text, const std::string& field_name) {
+    const std::string clean = trim_copy(text);
+    char* end = nullptr;
+    const auto value = std::strtoull(clean.c_str(), &end, 0);
+    if ((end == clean.c_str()) || (*end != '\0') || (value > std::numeric_limits<uint32_t>::max())) {
+        fail("Invalid integer for " + field_name + ": " + text);
+    }
+    return static_cast<uint32_t>(value);
+}
+
+double parse_double(const std::string& text, const std::string& field_name) {
+    const std::string clean = trim_copy(text);
+    char* end = nullptr;
+    const double value = std::strtod(clean.c_str(), &end);
+    if ((end == clean.c_str()) || (*end != '\0') || !std::isfinite(value)) {
+        fail("Invalid floating point value for " + field_name + ": " + text);
+    }
+    return value;
+}
+
+uint32_t parse_ipv4(const std::string& text) {
+    std::array<uint32_t, 4> parts{};
+    std::stringstream ss(text);
+    std::string token;
+    for (std::size_t i = 0; i < parts.size(); ++i) {
+        if (!std::getline(ss, token, '.')) {
+            fail("Invalid IPv4 address: " + text);
+        }
+        parts[i] = parse_u32(token, "ip");
+        if (parts[i] > 255U) {
+            fail("IPv4 byte out of range: " + token);
+        }
+    }
+    if (std::getline(ss, token, '.')) {
+        fail("Invalid IPv4 address: " + text);
+    }
+    return (parts[0] << 24U) | (parts[1] << 16U) | (parts[2] << 8U) | parts[3];
+}
+
+std::string ipv4_to_string(uint32_t ip_addr) {
+    std::ostringstream out;
+    out << ((ip_addr >> 24U) & 0xFFU) << '.'
+        << ((ip_addr >> 16U) & 0xFFU) << '.'
+        << ((ip_addr >> 8U) & 0xFFU) << '.'
+        << (ip_addr & 0xFFU);
+    return out.str();
+}
+
+uint32_t parse_clock_mode(const std::string& text) {
+    const std::string value = trim_copy(text);
+    if (value == "di_syn1_rise") {
+        return X502_SYNC_DI_SYN1_RISE;
+    }
+    if (value == "di_syn1_fall") {
+        return X502_SYNC_DI_SYN1_FALL;
+    }
+    fail("Only clock:di_syn1_rise or clock:di_syn1_fall are supported");
+}
+
+std::string clock_mode_to_string(uint32_t mode) {
+    switch (mode) {
+    case X502_SYNC_DI_SYN1_RISE:
+        return "di_syn1_rise";
+    case X502_SYNC_DI_SYN1_FALL:
+        return "di_syn1_fall";
+    default:
+        return "unknown";
+    }
+}
+
+void print_help(const char* exe_name) {
+    std::cout
+        << "Usage:\n"
+        << "  " << exe_name << " [serial:SN] [ip:192.168.0.10]\n"
+        << "                [clock:di_syn1_rise] [clock_hz:2000000]\n"
+        << "                [windows:1000]\n"
+        << "                [recv_block:8192] [recv_timeout_ms:50]\n"
+        << "                [clock_wait_ms:5000] [lchm_wait_ms:5000]\n"
+        << "                [buffer_words:262144] [step_words:8192]\n"
+        << "                [pullup_syn1] [pullup_syn2]\n"
+        << "\n"
+        << "Fixed counting scheme:\n"
+        << "  DI_SYN1 -> external clock; one synchronous DIN sample is one clock\n"
+        << "  DI_SYN2 -> LCHM window; rising edge starts, falling edge stops\n"
+        << "  DI2     -> extra digital level split into high/low clock counts\n"
+        << "\n"
+        << "If DI_SYN2 is already high at startup, the first partial LCHM is skipped\n"
+        << "until a clean low->high transition is observed.\n"
+        << "\n"
+        << "Example:\n"
+        << "  " << exe_name << " clock:di_syn1_rise clock_hz:2000000 windows:1000\n";
+}
+
+Config parse_args(int argc, char** argv) {
+    Config cfg;
+
+    for (int i = 1; i < argc; ++i) {
+        const std::string arg = argv[i];
+        if ((arg == "help") || (arg == "--help") || (arg == "-h")) {
+            print_help(argv[0]);
+            std::exit(0);
+        }
+        if (arg == "pullup_syn1") {
+            cfg.pullup_syn1 = true;
+            continue;
+        }
+        if (arg == "pullup_syn2") {
+            cfg.pullup_syn2 = true;
+            continue;
+        }
+        if (starts_with(arg, "serial:")) {
+            cfg.serial = arg.substr(7);
+            continue;
+        }
+        if (starts_with(arg, "ip:")) {
+            cfg.ip_addr = parse_ipv4(arg.substr(3));
+            continue;
+        }
+        if (starts_with(arg, "clock:")) {
+            cfg.clock_mode = parse_clock_mode(arg.substr(6));
+            continue;
+        }
+        if (starts_with(arg, "clock_hz:")) {
+            cfg.clock_hz = parse_double(arg.substr(9), "clock_hz");
+            continue;
+        }
+        if (starts_with(arg, "sample_clock_hz:")) {
+            cfg.clock_hz = parse_double(arg.substr(16), "sample_clock_hz");
+            continue;
+        }
+        if (starts_with(arg, "windows:")) {
+            cfg.windows = parse_u32(arg.substr(8), "windows");
+            continue;
+        }
+        if (starts_with(arg, "recv_block:")) {
+            cfg.recv_block_words = parse_u32(arg.substr(11), "recv_block");
+            continue;
+        }
+        if (starts_with(arg, "recv_timeout_ms:")) {
+            cfg.recv_timeout_ms = parse_u32(arg.substr(16), "recv_timeout_ms");
+            continue;
+        }
+        if (starts_with(arg, "clock_wait_ms:")) {
+            cfg.clock_wait_ms = parse_u32(arg.substr(14), "clock_wait_ms");
+            continue;
+        }
+        if (starts_with(arg, "lchm_wait_ms:")) {
+            cfg.lchm_wait_ms = parse_u32(arg.substr(13), "lchm_wait_ms");
+            continue;
+        }
+        if (starts_with(arg, "window_wait_ms:")) {
+            cfg.lchm_wait_ms = parse_u32(arg.substr(15), "window_wait_ms");
+            continue;
+        }
+        if (starts_with(arg, "buffer_words:")) {
+            cfg.input_buffer_words = parse_u32(arg.substr(13), "buffer_words");
+            continue;
+        }
+        if (starts_with(arg, "step_words:")) {
+            cfg.input_step_words = parse_u32(arg.substr(11), "step_words");
+            continue;
+        }
+        fail("Unknown argument: " + arg);
+    }
+
+    if (cfg.clock_hz <= 0.0) {
+        fail("clock_hz must be > 0");
+    }
+    if (cfg.windows == 0U) {
+        fail("windows must be > 0");
+    }
+    if (cfg.recv_block_words == 0U) {
+        fail("recv_block must be > 0");
+    }
+    if (cfg.input_step_words == 0U) {
+        cfg.input_step_words = cfg.recv_block_words;
+    }
+    if (cfg.input_buffer_words < cfg.recv_block_words) {
+        cfg.input_buffer_words = cfg.recv_block_words;
+    }
+
+    return cfg;
+}
+
+#ifdef _WIN32
+using ModuleHandle = HMODULE;
+#else
+using ModuleHandle = void*;
+#endif
+
+std::string dynamic_loader_error() {
+#ifdef _WIN32
+    return "unknown error";
+#else
+    const char* error = dlerror();
+    return ((error != nullptr) && (*error != '\0')) ? std::string(error) : std::string("unknown error");
+#endif
+}
+
+ModuleHandle open_library(const char* path) {
+#ifdef _WIN32
+    return LoadLibraryA(path);
+#else
+    dlerror();
+    return dlopen(path, RTLD_LAZY | RTLD_LOCAL);
+#endif
+}
+
+void close_library(ModuleHandle module) {
+#ifdef _WIN32
+    if (module != nullptr) {
+        FreeLibrary(module);
+    }
+#else
+    if (module != nullptr) {
+        dlclose(module);
+    }
+#endif
+}
+
+ModuleHandle load_library_or_fail(const std::vector<std::string>& candidates,
+                                  const std::string& description) {
+    std::string last_error = "no candidates provided";
+    for (const auto& candidate : candidates) {
+        ModuleHandle module = open_library(candidate.c_str());
+        if (module != nullptr) {
+            return module;
+        }
+        last_error = dynamic_loader_error();
+    }
+
+    std::ostringstream out;
+    out << "Cannot load " << description << ". Tried:";
+    for (const auto& candidate : candidates) {
+        out << " " << candidate;
+    }
+    out << ". Last error: " << last_error;
+    fail(out.str());
+}
+
+template <typename Fn>
+Fn load_symbol(ModuleHandle module, const char* name) {
+#ifdef _WIN32
+    const auto addr = GetProcAddress(module, name);
+    if (addr == nullptr) {
+        fail(std::string("GetProcAddress failed for symbol: ") + name);
+    }
+    return reinterpret_cast<Fn>(addr);
+#else
+    dlerror();
+    void* addr = dlsym(module, name);
+    const char* error = dlerror();
+    if ((addr == nullptr) || (error != nullptr)) {
+        std::ostringstream out;
+        out << "dlsym failed for symbol " << name << ": "
+            << ((error != nullptr) ? error : "unknown error");
+        fail(out.str());
+    }
+    return reinterpret_cast<Fn>(addr);
+#endif
+}
+
+template <typename Fn>
+Fn try_load_symbol(ModuleHandle module, const char* name) {
+#ifdef _WIN32
+    const auto addr = GetProcAddress(module, name);
+    return reinterpret_cast<Fn>(addr);
+#else
+    dlerror();
+    void* addr = dlsym(module, name);
+    (void) dlerror();
+    return reinterpret_cast<Fn>(addr);
+#endif
+}
+
+struct Api {
+    ModuleHandle x502_module = nullptr;
+    ModuleHandle e502_module = nullptr;
+
+    decltype(&X502_Create) Create = nullptr;
+    decltype(&X502_Free) Free = nullptr;
+    decltype(&X502_Close) Close = nullptr;
+    decltype(&X502_GetErrorString) GetErrorString = nullptr;
+    decltype(&X502_GetDevInfo) GetDevInfo = nullptr;
+    decltype(&X502_GetDevInfo2) GetDevInfo2 = nullptr;
+    decltype(&X502_SetMode) SetMode = nullptr;
+    decltype(&X502_StreamsStop) StreamsStop = nullptr;
+    decltype(&X502_StreamsDisable) StreamsDisable = nullptr;
+    decltype(&X502_SetSyncMode) SetSyncMode = nullptr;
+    decltype(&X502_SetSyncStartMode) SetSyncStartMode = nullptr;
+    decltype(&X502_SetDinFreqDivider) SetDinFreqDivider = nullptr;
+    decltype(&X502_SetStreamBufSize) SetStreamBufSize = nullptr;
+    decltype(&X502_SetStreamStep) SetStreamStep = nullptr;
+    decltype(&X502_SetDigInPullup) SetDigInPullup = nullptr;
+    decltype(&X502_SetExtRefFreqValue) SetExtRefFreqValue = nullptr;
+    decltype(&X502_Configure) Configure = nullptr;
+    decltype(&X502_StreamsEnable) StreamsEnable = nullptr;
+    decltype(&X502_StreamsStart) StreamsStart = nullptr;
+    decltype(&X502_GetRecvReadyCount) GetRecvReadyCount = nullptr;
+    decltype(&X502_Recv) Recv = nullptr;
+    decltype(&X502_ProcessData) ProcessData = nullptr;
+
+    decltype(&E502_OpenUsb) OpenUsb = nullptr;
+    decltype(&E502_OpenByIpAddr) OpenByIpAddr = nullptr;
+
+    Api() {
+        x502_module = load_library_or_fail(
+#ifdef _WIN32
+            {"x502api.dll"},
+#else
+            {"libx502api.so", "x502api.so", "./libx502api.so", "./x502api.so"},
+#endif
+            "x502 API library");
+        e502_module = load_library_or_fail(
+#ifdef _WIN32
+            {"e502api.dll"},
+#else
+            {"libe502api.so", "e502api.so", "./libe502api.so", "./e502api.so"},
+#endif
+            "e502 API library");
+
+        Create = load_symbol<decltype(Create)>(x502_module, "X502_Create");
+        Free = load_symbol<decltype(Free)>(x502_module, "X502_Free");
+        Close = load_symbol<decltype(Close)>(x502_module, "X502_Close");
+        GetErrorString = load_symbol<decltype(GetErrorString)>(x502_module, "X502_GetErrorString");
+        GetDevInfo = try_load_symbol<decltype(GetDevInfo)>(x502_module, "X502_GetDevInfo");
+        GetDevInfo2 = try_load_symbol<decltype(GetDevInfo2)>(x502_module, "X502_GetDevInfo2");
+        if ((GetDevInfo == nullptr) && (GetDevInfo2 == nullptr)) {
+            fail("Neither X502_GetDevInfo nor X502_GetDevInfo2 is available in x502 API library");
+        }
+        SetMode = load_symbol<decltype(SetMode)>(x502_module, "X502_SetMode");
+        StreamsStop = load_symbol<decltype(StreamsStop)>(x502_module, "X502_StreamsStop");
+        StreamsDisable = load_symbol<decltype(StreamsDisable)>(x502_module, "X502_StreamsDisable");
+        SetSyncMode = load_symbol<decltype(SetSyncMode)>(x502_module, "X502_SetSyncMode");
+        SetSyncStartMode = load_symbol<decltype(SetSyncStartMode)>(x502_module, "X502_SetSyncStartMode");
+        SetDinFreqDivider = load_symbol<decltype(SetDinFreqDivider)>(x502_module, "X502_SetDinFreqDivider");
+        SetStreamBufSize = load_symbol<decltype(SetStreamBufSize)>(x502_module, "X502_SetStreamBufSize");
+        SetStreamStep = load_symbol<decltype(SetStreamStep)>(x502_module, "X502_SetStreamStep");
+        SetDigInPullup = load_symbol<decltype(SetDigInPullup)>(x502_module, "X502_SetDigInPullup");
+        SetExtRefFreqValue = load_symbol<decltype(SetExtRefFreqValue)>(x502_module, "X502_SetExtRefFreqValue");
+        Configure = load_symbol<decltype(Configure)>(x502_module, "X502_Configure");
+        StreamsEnable = load_symbol<decltype(StreamsEnable)>(x502_module, "X502_StreamsEnable");
+        StreamsStart = load_symbol<decltype(StreamsStart)>(x502_module, "X502_StreamsStart");
+        GetRecvReadyCount = load_symbol<decltype(GetRecvReadyCount)>(x502_module, "X502_GetRecvReadyCount");
+        Recv = load_symbol<decltype(Recv)>(x502_module, "X502_Recv");
+        ProcessData = load_symbol<decltype(ProcessData)>(x502_module, "X502_ProcessData");
+
+        OpenUsb = load_symbol<decltype(OpenUsb)>(e502_module, "E502_OpenUsb");
+        OpenByIpAddr = load_symbol<decltype(OpenByIpAddr)>(e502_module, "E502_OpenByIpAddr");
+    }
+
+    ~Api() {
+        close_library(e502_module);
+        close_library(x502_module);
+    }
+};
+
+std::string x502_error(const Api& api, int32_t err) {
+    const char* text = api.GetErrorString ? api.GetErrorString(err) : nullptr;
+    std::ostringstream out;
+    out << "err=" << err;
+    if ((text != nullptr) && (*text != '\0')) {
+        out << " (" << text << ")";
+    }
+    return out.str();
+}
+
+void expect_ok(const Api& api, int32_t err, const std::string& what) {
+    if (err != X502_ERR_OK) {
+        fail(what + ": " + x502_error(api, err));
+    }
+}
+
+using TickMs = uint64_t;
+
+TickMs tick_count_ms() {
+#ifdef _WIN32
+    return static_cast<TickMs>(GetTickCount64());
+#else
+    using namespace std::chrono;
+    return static_cast<TickMs>(
+        duration_cast<milliseconds>(steady_clock::now().time_since_epoch()).count());
+#endif
+}
+
+#ifdef _WIN32
+volatile LONG g_console_stop_requested = 0;
+
+BOOL WINAPI console_ctrl_handler(DWORD ctrl_type) {
+    if ((ctrl_type == CTRL_C_EVENT) || (ctrl_type == CTRL_BREAK_EVENT) || (ctrl_type == CTRL_CLOSE_EVENT)) {
+        InterlockedExchange(&g_console_stop_requested, 1);
+        return TRUE;
+    }
+    return FALSE;
+}
+
+bool console_stop_requested() {
+    return InterlockedCompareExchange(&g_console_stop_requested, 0, 0) != 0;
+}
+#else
+volatile std::sig_atomic_t g_console_stop_requested = 0;
+
+void console_ctrl_handler(int) {
+    g_console_stop_requested = 1;
+}
+
+bool console_stop_requested() {
+    return g_console_stop_requested != 0;
+}
+#endif
+
+struct ConsoleCtrlGuard {
+    bool installed = false;
+
+    ConsoleCtrlGuard() {
+#ifdef _WIN32
+        installed = SetConsoleCtrlHandler(console_ctrl_handler, TRUE) != 0;
+#else
+        struct sigaction action {};
+        action.sa_handler = console_ctrl_handler;
+        sigemptyset(&action.sa_mask);
+        installed = (sigaction(SIGINT, &action, nullptr) == 0);
+#endif
+    }
+
+    ~ConsoleCtrlGuard() {
+#ifdef _WIN32
+        if (installed) {
+            SetConsoleCtrlHandler(console_ctrl_handler, FALSE);
+        }
+#else
+        if (installed) {
+            struct sigaction action {};
+            action.sa_handler = SIG_DFL;
+            sigemptyset(&action.sa_mask);
+            sigaction(SIGINT, &action, nullptr);
+        }
+#endif
+    }
+};
+
+struct DeviceHandle {
+    const Api& api;
+    t_x502_hnd hnd = nullptr;
+    bool opened = false;
+    bool streams_started = false;
+
+    explicit DeviceHandle(const Api& api_ref) : api(api_ref), hnd(api.Create()) {
+        if (hnd == nullptr) {
+            fail("X502_Create failed");
+        }
+    }
+
+    ~DeviceHandle() {
+        if (hnd != nullptr) {
+            if (streams_started) {
+                api.StreamsStop(hnd);
+            }
+            if (opened) {
+                api.Close(hnd);
+            }
+            api.Free(hnd);
+        }
+    }
+};
+
+void print_device_info(const t_x502_info& info) {
+    std::cout << "Device: " << info.name << "\n"
+              << "Serial: " << info.serial << "\n"
+              << "FPGA version: " << static_cast<unsigned>(info.fpga_ver >> 8U) << "."
+              << static_cast<unsigned>(info.fpga_ver & 0xFFU) << "\n"
+              << "PLDA version: " << static_cast<unsigned>(info.plda_ver) << "\n"
+              << "Board revision: " << static_cast<unsigned>(info.board_rev) << "\n"
+              << "MCU firmware: " << info.mcu_firmware_ver << "\n";
+}
+
+void print_summary(const RunningStats& stats) {
+    if (stats.count == 0U) {
+        std::cout << "No complete LCHM windows captured\n";
+        return;
+    }
+
+    const auto avg = [count = stats.count](uint64_t sum) {
+        return static_cast<double>(sum) / static_cast<double>(count);
+    };
+
+    std::cout << std::fixed << std::setprecision(3)
+              << "Summary: windows=" << stats.count << "\n"
+              << "  clocks: min=" << stats.clocks_min
+              << ", avg=" << avg(stats.clocks_sum)
+              << ", max=" << stats.clocks_max << "\n"
+              << "  di2_high_clocks: min=" << stats.high_min
+              << ", avg=" << avg(stats.high_sum)
+              << ", max=" << stats.high_max << "\n"
+              << "  di2_low_clocks: min=" << stats.low_min
+              << ", avg=" << avg(stats.low_sum)
+              << ", max=" << stats.low_max << "\n";
+}
+
+int run(const Config& cfg) {
+    Api api;
+    DeviceHandle device(api);
+
+    int32_t open_err = X502_ERR_OK;
+    if (cfg.ip_addr.has_value()) {
+        open_err = api.OpenByIpAddr(device.hnd, *cfg.ip_addr, 0, 5000);
+    } else {
+        open_err = api.OpenUsb(device.hnd, cfg.serial.empty() ? nullptr : cfg.serial.c_str());
+    }
+    expect_ok(api, open_err, cfg.ip_addr.has_value()
+        ? ("Open device by IP " + ipv4_to_string(*cfg.ip_addr))
+        : std::string("Open device over USB"));
+    device.opened = true;
+
+    t_x502_info info {};
+    int32_t info_err = X502_ERR_OK;
+    if (api.GetDevInfo2 != nullptr) {
+        info_err = api.GetDevInfo2(device.hnd, &info, sizeof(info));
+    } else {
+        info_err = api.GetDevInfo(device.hnd, &info);
+    }
+    expect_ok(api, info_err, "Get device info");
+    print_device_info(info);
+
+    expect_ok(api, api.SetMode(device.hnd, X502_MODE_FPGA), "Set FPGA mode");
+    api.StreamsStop(device.hnd);
+    api.StreamsDisable(device.hnd, X502_STREAM_ALL_IN | X502_STREAM_ALL_OUT);
+
+    expect_ok(api, api.SetSyncMode(device.hnd, cfg.clock_mode), "Set external clock on DI_SYN1");
+    expect_ok(api, api.SetSyncStartMode(device.hnd, X502_SYNC_INTERNAL), "Set immediate stream start");
+
+    const int32_t ext_ref_err = api.SetExtRefFreqValue(device.hnd, cfg.clock_hz);
+    if (ext_ref_err != X502_ERR_OK) {
+        if (cfg.clock_hz <= 1500000.0) {
+            expect_ok(api, ext_ref_err, "Set external reference frequency");
+        } else {
+            std::cerr << "Warning: X502_SetExtRefFreqValue(" << cfg.clock_hz
+                      << ") failed, continuing with DIN divider 1: "
+                      << x502_error(api, ext_ref_err) << "\n";
+        }
+    }
+
+    expect_ok(api, api.SetDinFreqDivider(device.hnd, 1), "Set DIN frequency divider to one clock");
+    expect_ok(api, api.SetStreamBufSize(device.hnd, X502_STREAM_CH_IN, cfg.input_buffer_words),
+              "Set input buffer size");
+    expect_ok(api, api.SetStreamStep(device.hnd, X502_STREAM_CH_IN, cfg.input_step_words),
+              "Set input stream step");
+
+    uint32_t pullups = 0;
+    if (cfg.pullup_syn1) {
+        pullups |= X502_PULLUPS_DI_SYN1;
+    }
+    if (cfg.pullup_syn2) {
+        pullups |= X502_PULLUPS_DI_SYN2;
+    }
+    expect_ok(api, api.SetDigInPullup(device.hnd, pullups), "Set digital input pullups");
+
+    expect_ok(api, api.Configure(device.hnd, 0), "Configure device");
+    expect_ok(api, api.StreamsEnable(device.hnd, X502_STREAM_DIN), "Enable DIN stream");
+
+    std::cout << "LCHM clock counter settings:\n"
+              << "  clock source: " << clock_mode_to_string(cfg.clock_mode) << "\n"
+              << "  nominal clock: " << cfg.clock_hz << " Hz\n"
+              << "  LCHM gate: DI_SYN2 high window\n"
+              << "  DI2 split: enabled\n"
+              << "  target windows: " << cfg.windows << "\n"
+              << "  recv block words: " << cfg.recv_block_words << "\n"
+              << "  input step words: " << cfg.input_step_words << "\n"
+              << "  input buffer words: " << cfg.input_buffer_words << "\n";
+
+    ConsoleCtrlGuard console_guard;
+    if (!console_guard.installed) {
+        std::cerr << "Warning: Ctrl+C handler could not be installed; stop may be abrupt.\n";
+    }
+
+    expect_ok(api, api.StreamsStart(device.hnd), "Start streams");
+    device.streams_started = true;
+
+    std::vector<uint32_t> raw(cfg.recv_block_words);
+    std::vector<uint32_t> din_buffer(cfg.recv_block_words);
+
+    bool gate_initialized = false;
+    bool last_gate = false;
+    bool saw_low_before_capture = false;
+    bool in_lchm = false;
+    LchmClockCount current;
+    RunningStats stats;
+
+    const TickMs session_start = tick_count_ms();
+    TickMs last_stream_activity = session_start;
+    TickMs last_lchm_complete = session_start;
+    TickMs last_din_activity = session_start;
+    TickMs last_gate_edge = session_start;
+
+    uint64_t total_raw_words = 0;
+    uint64_t total_din_words = 0;
+    uint64_t total_gate_edges = 0;
+
+    auto finalize_lchm = [&]() {
+        if (current.clocks != (current.di2_high_clocks + current.di2_low_clocks)) {
+            std::ostringstream message;
+            message << "DI2 clock split invariant failed: clocks=" << current.clocks
+                    << ", high=" << current.di2_high_clocks
+                    << ", low=" << current.di2_low_clocks;
+            fail(message.str());
+        }
+
+        if (current.clocks != 0U) {
+            const uint64_t lchm_index = stats.count + 1U;
+            stats.add(current);
+            std::cout << "LCHM " << lchm_index
+                      << ": clocks=" << current.clocks
+                      << ", di2_high_clocks=" << current.di2_high_clocks
+                      << ", di2_low_clocks=" << current.di2_low_clocks
+                      << "\n";
+            last_lchm_complete = tick_count_ms();
+        }
+        current.clear();
+    };
+
+    auto fail_waiting_for_lchm = [&](TickMs now) {
+        std::ostringstream message;
+        message << "ADC/DIN clock is present, but no complete DI_SYN2 LCHM window was captured within "
+                << cfg.lchm_wait_ms << " ms. "
+                << "DIN samples=" << total_din_words
+                << ", gate edges=" << total_gate_edges << ". ";
+
+        if (total_din_words == 0U) {
+            message << "No synchronous DIN words were decoded. ";
+        } else if (!gate_initialized) {
+            message << "DIN data is present, but DI_SYN2 state was not initialized yet. ";
+        } else if (total_gate_edges == 0U) {
+            message << "DI_SYN2 appears stuck " << (last_gate ? "HIGH" : "LOW") << ". ";
+        } else if (in_lchm) {
+            message << "DI_SYN2 produced a rising edge, but no matching falling edge closed the LCHM. ";
+        } else {
+            message << "DI_SYN2 toggled, but no complete low->high->low LCHM was accepted. ";
+        }
+
+        message << "Check DI_SYN2 wiring, common DGND, and signal level around 0/3.3 V. "
+                << "Progress: last DIN activity " << (now - last_din_activity)
+                << " ms ago, last DI_SYN2 edge " << (now - last_gate_edge) << " ms ago.";
+        fail(message.str());
+    };
+
+    while ((stats.count < cfg.windows) && !console_stop_requested()) {
+        uint32_t recv_request_words = cfg.recv_block_words;
+        uint32_t recv_timeout_ms = cfg.recv_timeout_ms;
+        uint32_t ready_words = 0;
+        const int32_t ready_err = api.GetRecvReadyCount(device.hnd, &ready_words);
+        if ((ready_err == X502_ERR_OK) && (ready_words != 0U)) {
+            recv_request_words = std::min<uint32_t>(ready_words, cfg.recv_block_words);
+            recv_timeout_ms = 0;
+        }
+
+        const int32_t recvd = api.Recv(device.hnd, raw.data(), recv_request_words, recv_timeout_ms);
+        if (recvd < 0) {
+            fail("X502_Recv failed: " + x502_error(api, recvd));
+        }
+
+        const TickMs now = tick_count_ms();
+        if (recvd == 0) {
+            if ((now - last_stream_activity) >= cfg.clock_wait_ms) {
+                fail("Timeout waiting for external clock on DI_SYN1. "
+                     "The stream starts immediately, so this usually means there is no valid clock on DI_SYN1.");
+            }
+            if ((now - last_lchm_complete) >= cfg.lchm_wait_ms) {
+                fail_waiting_for_lchm(now);
+            }
+            continue;
+        }
+
+        last_stream_activity = now;
+        total_raw_words += static_cast<uint64_t>(recvd);
+
+        uint32_t din_count = static_cast<uint32_t>(din_buffer.size());
+        expect_ok(api,
+                  api.ProcessData(device.hnd,
+                                  raw.data(),
+                                  static_cast<uint32_t>(recvd),
+                                  0U,
+                                  nullptr,
+                                  nullptr,
+                                  din_buffer.data(),
+                                  &din_count),
+                  "Process DIN data");
+
+        if (din_count != 0U) {
+            total_din_words += din_count;
+            last_din_activity = now;
+        }
+
+        for (uint32_t i = 0; (i < din_count) && (stats.count < cfg.windows); ++i) {
+            const uint32_t din_value = din_buffer[i];
+            const bool gate = (din_value & kE502DiSyn2Mask) != 0U;
+            const bool di2_high = (din_value & kE502Digital2Mask) != 0U;
+
+            if (!gate_initialized) {
+                gate_initialized = true;
+                last_gate = gate;
+                saw_low_before_capture = !gate;
+                last_gate_edge = now;
+            } else if (!saw_low_before_capture && !gate) {
+                saw_low_before_capture = true;
+            }
+
+            if (gate_initialized && (gate != last_gate)) {
+                ++total_gate_edges;
+                last_gate_edge = now;
+            }
+
+            if (!in_lchm && saw_low_before_capture && gate_initialized && !last_gate && gate) {
+                in_lchm = true;
+                current.clear();
+            }
+
+            if (in_lchm && !gate) {
+                finalize_lchm();
+                in_lchm = false;
+            }
+
+            if (in_lchm && gate) {
+                current.add(di2_high);
+            }
+
+            last_gate = gate;
+        }
+
+        if ((stats.count < cfg.windows) && ((now - last_lchm_complete) >= cfg.lchm_wait_ms)) {
+            fail_waiting_for_lchm(now);
+        }
+    }
+
+    if (console_stop_requested() && in_lchm) {
+        finalize_lchm();
+    }
+
+    expect_ok(api, api.StreamsStop(device.hnd), "Stop streams");
+    device.streams_started = false;
+
+    std::cout << "Raw words read: " << total_raw_words
+              << ", DIN samples: " << total_din_words
+              << ", DI_SYN2 edges: " << total_gate_edges << "\n";
+    print_summary(stats);
+
+    return 0;
+}
+
+} // namespace
+
+int main(int argc, char** argv) {
+    try {
+        const Config cfg = parse_args(argc, argv);
+        return run(cfg);
+    } catch (const std::exception& ex) {
+        std::cerr << "Error: " << ex.what() << "\n";
+        return 1;
+    }
+}
diff --git a/main.cpp b/main.cpp
index d93f0fc..1d357d1 100644
--- a/main.cpp
+++ b/main.cpp
@@ -1008,6 +1008,7 @@ void expect_ok(const Api& api, int32_t err, const std::string& what) {
 constexpr uint32_t kE502DiSyn2Mask =
     (static_cast<uint32_t>(1U) << 13U) | (static_cast<uint32_t>(1U) << 17U);
 constexpr uint32_t kE502Digital1Mask = (static_cast<uint32_t>(1U) << 0U);
+constexpr uint32_t kE502Digital2Mask = (static_cast<uint32_t>(1U) << 1U);
 constexpr uint32_t kStreamInputAdcFlag = 0x80000000U;
 constexpr uint32_t kStreamInputCalibratedAdcFlag = 0x40000000U;
 
@@ -1497,6 +1498,9 @@ int run(const Config& cfg) {
     std::size_t csv_global_frame_index = 0;
     std::size_t packet_avg_steps = 0;
     std::size_t fast_packet_frames = 0;
+    uint64_t packet_clock_count = 0;
+    uint64_t packet_di2_high_clocks = 0;
+    uint64_t packet_di2_low_clocks = 0;
 
     bool capture_started = false;
     bool stop_loop_requested = false;
@@ -1634,6 +1638,9 @@ int run(const Config& cfg) {
         }
         packet_avg_steps = 0;
         fast_packet_frames = 0;
+        packet_clock_count = 0;
+        packet_di2_high_clocks = 0;
+        packet_di2_low_clocks = 0;
         if (!fast_tty_avg_stream_mode) {
             current_packet.reset(target_frames, cfg.channel_count);
         }
@@ -1645,6 +1652,14 @@ int run(const Config& cfg) {
     };
 
     auto finish_packet = [&](PacketCloseReason reason) {
+        if (packet_clock_count != (packet_di2_high_clocks + packet_di2_low_clocks)) {
+            std::ostringstream message;
+            message << "DI2 clock split invariant failed: clocks=" << packet_clock_count
+                    << ", high=" << packet_di2_high_clocks
+                    << ", low=" << packet_di2_low_clocks;
+            fail(message.str());
+        }
+
         if (tty_di1_group_average) {
             append_tty_group_step();
             tty_group_state.clear_step();
@@ -1662,6 +1677,9 @@ int run(const Config& cfg) {
                           << ": frames/ch=" << frames
                           << ", duration_ms=" << packet_duration_ms
                           << ", close_reason=" << packet_close_reason_to_string(reason)
+                          << ", clocks=" << packet_clock_count
+                          << ", di2_high_clocks=" << packet_di2_high_clocks
+                          << ", di2_low_clocks=" << packet_di2_low_clocks
                           << ", avg_steps=" << packet_avg_steps
                           << "\n";
             } else {
@@ -1694,7 +1712,10 @@ int run(const Config& cfg) {
                           << "Packet " << packet.packet_index
                           << ": frames/ch=" << frames
                           << ", duration_ms=" << packet_duration_ms
-                          << ", close_reason=" << packet_close_reason_to_string(reason);
+                          << ", close_reason=" << packet_close_reason_to_string(reason)
+                          << ", clocks=" << packet_clock_count
+                          << ", di2_high_clocks=" << packet_di2_high_clocks
+                          << ", di2_low_clocks=" << packet_di2_low_clocks;
                 if (cfg.di1_mode == Di1Mode::ZeroOnChange) {
                     std::cout << ", zeroed_on_DI1_change=" << zeroed_fraction << "% ("
                               << current_packet.zeroed_samples << "/" << current_packet.stored_samples << ")";
@@ -1752,6 +1773,9 @@ int run(const Config& cfg) {
         packet_active = false;
         packet_avg_steps = 0;
         fast_packet_frames = 0;
+        packet_clock_count = 0;
+        packet_di2_high_clocks = 0;
+        packet_di2_low_clocks = 0;
         if (!fast_tty_avg_stream_mode) {
             current_packet.reset(target_frames, cfg.channel_count);
         }
@@ -2009,6 +2033,13 @@ int run(const Config& cfg) {
                 continue;
             }
 
+            if ((din_value & kE502Digital2Mask) != 0U) {
+                ++packet_di2_high_clocks;
+            } else {
+                ++packet_di2_low_clocks;
+            }
+            ++packet_clock_count;
+
             if (tty_di1_group_average && di1_changed) {
                 append_tty_group_step();
                 tty_group_state.clear_step();
diff --git a/tty_protocol_writer.cpp b/tty_protocol_writer.cpp
index 5c8f074..f7e5c43 100644
--- a/tty_protocol_writer.cpp
+++ b/tty_protocol_writer.cpp
@@ -265,7 +265,7 @@ void TtyProtocolWriter::emit_packet_start(uint16_t marker) {
 }
 
 void TtyProtocolWriter::emit_step(uint16_t index, int16_t ch1_avg, int16_t ch2_avg) {
-    enqueue_frame( (cfg.profile == CaptureProfile::Amplitude) ? 0x001AU : 0x000AU,
+    enqueue_frame(0x000A,
                   index,
                   static_cast<uint16_t>(ch1_avg),
                   static_cast<uint16_t>(ch2_avg));