# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1496595308 -7200
# Node ID 616e71c2d754145d0a6ba926ba97bc9f1015fd1a
# Parent  ea8642c174958df5e3f65221e2f06aafe8209f2d
lpt-signal-generator: měření času stráveného v outb()

diff -r ea8642c17495 -r 616e71c2d754 c++/lpt-signal-generator/lpt.cpp
--- a/c++/lpt-signal-generator/lpt.cpp	Sun Jun 04 14:59:13 2017 +0200
+++ b/c++/lpt-signal-generator/lpt.cpp	Sun Jun 04 18:55:08 2017 +0200
@@ -22,6 +22,7 @@
 #include <math.h>
 #include <sys/io.h>
 #include <unistd.h>
+#include <chrono> // requires -std=c++11
 
 /**
  * can not mix printf and wprintf
@@ -37,8 +38,8 @@
 
 using namespace std;
 
-// run this program: g++ lpt.cpp && time chrt 1 ./a.out
-// depending to frequency and machine performance the total time will be more than given duration
+// run this program: g++ -std=c++11 lpt.cpp && time chrt 1 ./a.out
+// depending on frequency and machine performance the total time will be more than given duration
 // despite the real-time priority, because some additional time is spent in outb() functions
 // so "duration" means total sleep time
 
@@ -56,17 +57,17 @@
   int addr = 0xe400; // parallel port address; first number of given port in: cat /proc/ioports | grep parport
   int baseFreq = 10000; // base frequency in Hz, should be between 5 000 between 10 000 Hz; lower frequency leads to dashed/dotted lines instead of greyscale
   int outputPower = 10; // duty cycle; 100 = 100 %
-  int duration = 5; // in seconds; total sleep time, see note above
+  int duration = 1; // in seconds; total sleep time, see note above
 
   int valueWidth =  10; // just for padding of printed values
   int labelWidth = -15; // just for padding of printed labels
 
   // ' = thousand separator
   // * = padding
-  wprintf(L"%*ls %*x\n",     labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix
+  wprintf(L"%*ls %*x\n", labelWidth, L"Parallel port:", valueWidth, addr); // or %#*x – adds 0x prefix
   wprintf(L"%*ls %'*d Hz\n", labelWidth, L"Base frequency:", valueWidth, baseFreq);
-  wprintf(L"%*ls %*d %%\n",  labelWidth, L"Output power:", valueWidth, outputPower);
-  wprintf(L"%*ls %'*d s\n",  labelWidth, L"Duration:", valueWidth, duration);
+  wprintf(L"%*ls %*d %% duty cycle\n",  labelWidth, L"Output power:", valueWidth, outputPower);
+  wprintf(L"%*ls %'*d s\n", labelWidth, L"Duration:", valueWidth, duration);
 
   // in microseconds:
   int oneSecond = 1000 * 1000;
@@ -75,23 +76,29 @@
 
   int cycleCount = duration * baseFreq;
   wprintf(L"%*ls %'*d ×\n", labelWidth, L"Cycle count:", valueWidth, cycleCount);
-  wprintf(L"%*ls %'*d μs in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);
-  wprintf(L"%*ls %'*d μs in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);
+  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time on:",  valueWidth, timeOn);
+  wprintf(L"%*ls %'*d μs 1× in each cycle\n", labelWidth, L"Time off:", valueWidth, timeOff);
 
-  wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");
+  //wprintf(L"%*ls %*ls\n", labelWidth, L"unicode test:", valueWidth, L"čeština → …");
 
 
   if (ioperm(addr,1,1)) { fwprintf(stderr, L"Access denied to port %#x\n", addr), exit(1); }
 
   outb(0b00000000, addr);
 
+  auto startTimestamp = chrono::high_resolution_clock::now();
+
   for (int i = 0; i < cycleCount; i++) {
-    outb(0b00000001, addr);
+    outb(0b00000001, addr); // first data out pin = data out 0 = pin 2 on DB-25 connector
     usleep(timeOn);
     outb(0b00000000, addr);
     usleep(timeOff);
   }
 
-  wprintf(L"finished\n");
+  auto finishTimestamp = chrono::high_resolution_clock::now();
+  auto measuredDuration = chrono::duration_cast<chrono::nanoseconds>(finishTimestamp - startTimestamp).count();
+
+  wprintf(L"%*ls %'*d μs 2× in each cycle\n", labelWidth, L"single outb():", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount/2/1000);
+  wprintf(L"%*ls %'*d ns 2× in each cycle\n", labelWidth, L"single outb():", valueWidth, (measuredDuration-duration*oneSecond*1000)/cycleCount/2);
 
 }