multiplexer.c: wait based on timers to counter measure any fluctuations

1 files changed, 30 insertions, 2 deletions

diff --git a/multiplexer.c b/multiplexer.c
index a8df74c..7fe0d3d 100644
--- a/multiplexer.c
+++ b/multiplexer.c
@@ -62,6 +62,9 @@ void *put_on_display(void *param)
 {
   t_display_data *display_data = param;
   int line, column;
+#ifndef SKIP_GPIO
+  struct timespec start_time, stop_time;
+#endif
 
   while (display_data -> keep_running) {
 
@@ -80,6 +83,11 @@ void *put_on_display(void *param)
 #else
     for (line=7; line>=0; line--) {
       GPIO_CLR = 1<<GATE_PIN; // Licht an
+      if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time) != 0) {
+        display_data -> keep_running = 0;
+        perror("clock_gettime failed");
+        break;
+      }
       for (column=0; column<8; column++) {
         GPIO_CLR = 1<<SER_CLK_PIN;
         GPIO_ALTER(column + line == 7) = 1<<SER_DAT_PIN;
@@ -98,6 +106,13 @@ void *put_on_display(void *param)
 #ifdef SKIP_GPIO
       printf("\n");
 #else
+      if (clock_gettime(CLOCK_MONOTONIC_RAW, &stop_time) != 0) {
+        display_data -> keep_running = 0;
+        perror("clock_gettime failed");
+        break;
+      }
+      // wait until start_time + 1ms
+      usleep((start_time.tv_sec - stop_time.tv_sec) * 1000000 + (start_time.tv_nsec - stop_time.tv_nsec) / 1000 + 1000);
       GPIO_SET = 1<<GATE_PIN; // Licht aus
       usleep(5);
       GPIO_CLR = 1<<PAR_CLK_PIN;
@@ -120,7 +135,14 @@ void *scroll_it(void *param)
   multiplexer_setup_non_root(&display_data);
   int is_buf = 0;
   int column = 0;
+  struct timespec start_time, stop_time;
+
   while (scroll_data -> keep_running) {
+    if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time) != 0) {
+      scroll_data -> keep_running = 0;
+      perror("clock_gettime failed");
+      break;
+    }
     if (scroll_data -> update) {
       if ((buf[is_buf] . len != scroll_data -> input_len) || (memcmp(&buf[is_buf] . buf[buf[is_buf] . start], scroll_data -> input, scroll_data -> input_len) != 0)) {
         is_buf = (is_buf + 1) % 2;
@@ -144,12 +166,18 @@ void *scroll_it(void *param)
     for (int i=0; i<40; i++)
       display_data . buf[(display_data . should_buf + 1) % 3][i] =
         buf[is_buf] . buf[column + i];
-    display_data . should_buf = (display_data . should_buf + 1) % 3;
     column++;
     if (buf[is_buf] . len > 0)
       while (column >= buf[is_buf] . start + buf[is_buf] . len)
         column -= buf[is_buf] . len;
-    usleep(50000);
+    if (clock_gettime(CLOCK_MONOTONIC_RAW, &stop_time) != 0) {
+      scroll_data -> keep_running = 0;
+      perror("clock_gettime failed");
+      break;
+    }
+    // wait until start_time + 50ms
+    usleep((start_time.tv_sec - stop_time.tv_sec) * 1000000 + (start_time.tv_nsec - stop_time.tv_nsec) / 1000 + 50000);
+    display_data . should_buf = (display_data . should_buf + 1) % 3;
   }
   display_data . keep_running = 0;
   pthread_join(display_data . thread_id, NULL);