Add test code for using RTT

due_obd2/due_obd2.ino

@@ -11,9 +11,10 @@ Program to create a car monitor display using:
 #include <UTFT.h>
 
 #include "obd2_display.h"
-// #include "obd2_timer.h"
+#include "obd2_timer.h"
 
 #define DEBUG 1
+// #define RTT_MR 0x400E1A30U
 
 /* pins */
 #define PIN_BT_RX 19
@@ -24,6 +25,8 @@ extern uint8_t BigFont[];
 extern uint8_t SmallFont[];
 
 char should_clear = 1;
+char led_state = LOW;
+char flag = 0;
 
 /* Set the pins for the display and dev board                                */
 /* Standard Arduino Mega/Due shield            : <display model>,38,39,40,41 */
@@ -46,7 +49,16 @@ void setup() {
   Serial.println("Starting");
   #endif
 
-  TCCR0A=(1<<WGM01);    //Set the CTC mode   
+  pinMode(LED_BUILTIN, OUTPUT);
+
+  obd2_timer_init();
+
+}
+
+void RTT_Handler()
+{
+  flag = 0;
+  obd2_timer_reset();
 }
 
 void loop() {
@@ -68,4 +80,14 @@ void loop() {
     delay(10);
     should_clear = 0;
   }
+
+  if (!flag)
+  {
+    led_state = ~led_state;
+    digitalWrite(LED_BUILTIN, led_state);
+    flag = 1;
+    #if (DEBUG == 1)
+    Serial.println("switching led");
+    #endif
+  }
 }

due_obd2/obd2_display.h

@@ -0,0 +1,15 @@
+#ifndef OBD2_DISPLAY_H
+#define OBD2_DISPLAY_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+/* display size */
+#define LCD_W 480
+#define LCD_H 320
+
+#ifdef __cplusplus
+}
+#endif
+#endif // !OBD2_DISPLAY_H

due_obd2/obd2_timer.c

@@ -0,0 +1,32 @@
+// #include "sam3xa/include/component/component_rtt.h"
+// #include "sam3xa/include/sam3x8e.h"
+#include "obd2_timer.h"
+
+void obd2_timer_init(void)
+{
+    /* enable the timer: reset the RTT, enable the alarm interrupt, set the prescaler value equal to the processor clock speed*/
+    RTT->RTT_MR = RTT_MR_RTTRST | RTT_MR_ALMIEN | RTT_MR_RTPRES(32768/2);
+    /* set the alarm value to 0*/
+    RTT->RTT_AR = 0;
+    /* enable the interrupt*/
+    NVIC_EnableIRQ(RTT_IRQn);
+}
+
+void obd2_timer_reset()
+{
+    /* To prevent several executions of the interrupt handler,
+     the interrupt must be disabled in the interrupt handler
+     and re-enabled when the status register is cleared.
+  */
+  /* disable interrupts */
+  RTT->RTT_MR &= ~RTT_MR_ALMIEN;
+  /* clear the status register */
+  RTT->RTT_SR;
+  /* set the alarm value to 0*/
+  RTT->RTT_AR = 0;
+  /* re-enable the interrupt*/
+  RTT->RTT_MR |= RTT_MR_ALMIEN;
+  /* reset the RTT*/
+  RTT->RTT_MR |= RTT_MR_RTTRST;
+
+}

due_obd2/obd2_timer.h

@@ -0,0 +1,17 @@
+#ifndef OBD2_TIMER_H
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+#include "Arduino.h"
+
+#define CLOCK_FREQ 32768
+
+void obd2_timer_init();
+void obd2_timer_reset();
+
+#ifdef __cplusplus
+}
+#endif
+#endif // !OBD2_TIMER_H