Do Shift Demo

DO Shift Demo — digital output bit walk

Source: do_shift_demo/main.cpp

Walks a single active bit across 16 digital outputs on a CiA401 I/O module, one bit per second.

---

1. Config & prepare

lxmaster::NetworkConfig cfg = lxmaster::NetworkConfig::defaults();
cfg.eni.eni_path = "/home/user/myenifolder/myenifile.xml";

lxmaster::EcNetwork net(cfg);
net.prepare();

NetworkConfig::defaults() reads the EtherCAT interface name from the environment (set by lxmaster host setup). The ENI file describes the bus topology and PDO layout — prepare() parses it and brings all slaves to PreOP.

---

2. Find IO module & configure

lxmaster::IoModule* mod = nullptr;
for (lxmaster::IoModule* m : net.ioModules()) {
    if (m->digitalOutputCount() >= kNumBits) { mod = m; break; }
}
mod->configure();

net.ioModules() returns every CiA401 I/O module found in the ENI. The first one with at least 16 digital outputs is selected. Calling configure() opts it into the OPERATIONAL bring-up — devices without configure() stay at PreOP.

---

3. Start

net.start();
for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(ch, false);

net.start() launches the real-time cyclic thread. All outputs are cleared to a known state before the walk begins.

---

4. Walk loop

while (net.isRunning() && !g_interrupted) {
    const int bit = static_cast<int>(elapsed_seconds / kBitIntervalS);
    if (bit >= kNumBits) break;

    if (bit != active_bit) {
        active_bit = bit;
        for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(ch, false);
        mod->writeDigital(bit, true);
    }
    std::this_thread::sleep_for(std::chrono::milliseconds(50));
}

The current bit index is derived from elapsed time. When it advances, all outputs are cleared and only the new bit is set high with writeDigital(). The loop polls at 50 ms — much slower than the EtherCAT cycle — because the bit interval is one full second.

---

5. Stop

for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(ch, false);
net.stop();

All outputs are cleared before net.stop() tears down the bus.

Source: main.cpp

#include <atomic>
#include <chrono>
#include <csignal>
#include <cstddef>
#include <iostream>
#include <thread>

#include <lxmaster/lxmaster.hpp>

static std::atomic<bool> g_interrupted{false};

constexpr int    kNumBits      = 16;
constexpr double kBitIntervalS = 1.0;

int main() {
  signal(SIGINT,  [](int){ g_interrupted = true; });
  signal(SIGTERM, [](int){ g_interrupted = true; });

  // --- 1. Config & prepare ---
  lxmaster::NetworkConfig cfg = lxmaster::NetworkConfig::defaults();
  cfg.eni.eni_path = "/home/user/myenifolder/myenifile.xml";

  lxmaster::EcNetwork net(cfg);
  if (!net.prepare()) { std::cerr << "prepare failed: " << net.lastError() << "\n"; return 1; }

  // --- 2. Find IO module & configure ---
  lxmaster::IoModule* mod = nullptr;
  for (lxmaster::IoModule* m : net.ioModules()) {
    if (m->digitalOutputCount() >= static_cast<std::size_t>(kNumBits)) { mod = m; break; }
  }
  if (!mod) { std::cerr << "No IO module with >= " << kNumBits << " digital outputs.\n"; return 1; }
  mod->configure();

  // --- 3. Start ---
  if (!net.start()) { std::cerr << "start failed: " << net.lastError() << "\n"; return 1; }
  for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(static_cast<std::size_t>(ch), false);
  std::this_thread::sleep_for(std::chrono::milliseconds(50));

  // --- 4. Walk loop ---
  const auto start = std::chrono::steady_clock::now();
  int active_bit = -1;

  while (net.isRunning() && !g_interrupted) {
    const auto now = std::chrono::steady_clock::now();
    const int bit  = static_cast<int>(std::chrono::duration<double>(now - start).count() / kBitIntervalS);
    if (bit >= kNumBits) break;

    if (bit != active_bit) {
      active_bit = bit;
      for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(static_cast<std::size_t>(ch), false);
      mod->writeDigital(static_cast<std::size_t>(bit), true);
      std::cout << "Bit " << bit << " ON\n";
    }
    std::this_thread::sleep_for(std::chrono::milliseconds(50));
  }

  // --- 5. Stop ---
  for (int ch = 0; ch < kNumBits; ++ch) mod->writeDigital(static_cast<std::size_t>(ch), false);
  net.stop();
  return 0;
}