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--- code:interrupt_driven_ubx [2009/05/01 00:07] – created laurenceb
+++ code:interrupt_driven_ubx [2009/05/11 20:17] (current) – laurenceb
@@ Line 1: / Line 1: @@
 under construction...
+===== demo code =====
 <code c>
+#include <stdlib.h>
+#include <stdio.h>
+#include <avr/interrupt.h>
+#include <avr/io.h>
+#include "ubx.h"
+volatile ubx_gps_type Gps;
-static u08 state,lenght,class,id;
+int uart_putchar(char c, FILE *stream)
-static gps_type gps;
-switch(state)
 {
-	case 0:				//start be waiting for the first sync byte
+	if (c == '\n')
-		if(c==SYNC_1)
+		uart_putchar('\r', stream);
-			state=1;
+	loop_until_bit_is_set(UCSR0A, UDRE0);
-		else
+	UDR0 = c;
-			state=0;
+	return 0;
-		break;
+}
-	case 1:				//followed by the second one
+static FILE mystdout = FDEV_SETUP_STREAM(uart_putchar,NULL,_FDEV_SETUP_WRITE);
-		if(c==SYNC_2)
-			state=2;
-		else
+void main(void)
-			state=0;
+{
-		break;
+	UCSR0B = (1<<RXCIE0)|(1<<RXEN0)|(1<<TXEN0);//mega xx8 registers - enable tx and rx, with interrupts on RX only
-	case 2:				//then store the class
+	UCSR0C = (1<<UCSZ01)|(1<<UCSZ00);	//setup 8N1
-		class=c;
+	UBRR0L = BAUDDIV;
-		state=3;
+	UBRR0H = BAUDDIV>>8;			//end of UART setup
-		break;
+	DDRD|=0x20;				//use portd 5 as an output for led
-	case 3:				//then the id
+	stdout = &mystdout;
-		id=c;
+	sei();					//enable interrupts
-		state=4;
+	TOGGLE_PIN;
-		break;
+	for(;;)
-	case 4:				//the least significant byte of the lenght
+	{
-		lenght=c;
+		if(Gps.packetflag==REQUIRED_DATA)
-		state=5;
-		break;
-	case 5:				//the most significant byte
-		lenght|=c<<8;
-		break;
-	case 6:				//the data follows
-		lenght--;
-		if(!lenght)		//we have reached the end of the data
-			state=7;
-		if(class==NAV)		//we have nav data
 		{
-			if(id==LLH)	//needs macros defining in the header file for the correct data positions
+			printf("%li,%li,%li,%2X,%2X\n",Gps.latitude,Gps.longitude,Gps.altitude,Gps.status,Gps.nosats);
+			Gps.packetflag=0;	//unlock the data
+		}
+	}
+}
+ISR(USART_RX_vect)				//UART interrupt on mega xx8 series
+{
+	static u08 state,class,id,checksum_1,checksum_2,counter;
+	static u16 lenght;
+	static ubx_gps_type gps;
+	u08 c = UDR0;
+	switch(state)
+	{
+		case 0:				//start be waiting for the first sync byte
+			if(c==SYNC_1)
+				state=1;
+			else
+				state=0;
+			break;
+		case 1:				//followed by the second one
+			if(c==SYNC_2)
+				state=2;
+			else
+				state=0;
+			break;
+		case 2:				//then store the class
+			class=c;
+			state=3;
+			break;
+		case 3:				//then the id
+			id=c;
+			state=4;
+			break;
+		case 4:				//the least significant byte of the lenght
+			lenght=c;
+			state=5;
+			break;
+		case 5:				//the most significant byte
+			lenght|=c<<8;
+			counter=0;
+			state=6;
+			break;
+		case 6:				//the data follows
+			if(class==NAV_CLASS)	//we have nav data
 			{
-				if(lenght<POS_END && lenght>POS_START)
+				if(id==LLH_DATA)//needs macros defining in the header file for the correct data positions
-					gps[lenght+POS_OFFSET]=c;
+				{
+					if(lenght<POS_END && lenght>POS_START)
+						((u08*)&gps)[POS_OFFSET-lenght]=c;
+				}
+				if(id==VELNED_DATA)
+				{
+					if(lenght<VEL_END && lenght>VEL_START)
+						((u08*)&gps)[VEL_OFFSET-lenght]=c;
+				}
+				if(id==SOL_DATA && lenght==SOL_POS)
+					gps.status=c;
+				if(id==SOL_DATA && lenght==SATS_POS)
+					gps.nosats=c;
+				/*if(id==SVINFO_DATA)//this appears to find the number of hardware channels avaliable
+				{
+					counter++;//this counts from the start of data
+					if(counter==SATS_POS)
+						gps.nosats=c;
+				}*/
 			}
-			if(id==VELNED)
+			lenght--;
+			if(!lenght)		//we have reached the end of the data
+				state=7;
+			break;
+		case 7:				//check the checksum
+			if(checksum_1==c)
+				state=8;
+			else
+				state=0;
+			break;
+		case 8:				//second byte of the checksum
+			if(checksum_2==c)
 			{
-				if(lenght<VEL_END && lenght>VEL_START)
+				if(class==NAV_CLASS)//if the class was NAV and we have valid id
-					gps[lenght+VEL_OFFSET]=c;
+				{
+					if(id==SVINFO_DATA)
+						gps.packetflag|=0x08;
+					if(id==SOL_DATA)
+						gps.packetflag|=0x04;
+					if(id==LLH_DATA)
+						gps.packetflag|=0x02;
+					if(id==VELNED_DATA)
+						gps.packetflag|=0x01;
+				}
+				if(!Gps.packetflag && gps.packetflag==REQUIRED_DATA)//main has unlocked the data and we have all the required data
+				{
+					TOGGLE_PIN;//toggles pin D5 - flashing LED tells us gps is working
+					Gps=gps;//copy into the global variable
+					gps.packetflag=0;//we now wait for more data to arrive
+				}		//complete
 			}
-		}
-		break;
-	case 7:				//check the checksum
-		if(checksum_1==c)
-			state=8;
-		else
 			state=0;
-		break;
+	}
-	case 8:				//second byte of the checksum
+	if(state>2 && state<8)			//in the valid range to add to the checksum
-		if(checksum_2==c)
+	{
-			if(class==NAV)	//if the class was NAV and we have valid id
+		checksum_1+=c;
-			{
+		checksum_2+=checksum_1;
-				if(id==LLH)
+	}
-					gps.packetflag|=LLH_DATA;
+	else if(!state)
-				if(id==VELNED)
+	{
-					gps.packetflag|=VELNED_DATA;
+		checksum_1=0;
-			}
+		checksum_2=0;
-			if(!Gps.packetflag && gps.packetflag==REQUIRED_DATA)//main has unlocked the data and we have all the required data
+	}
-			{
-				toggle_pin;//toggles pin D5 - flashing LED tells us gps is working
-				Gps=gps;//copy into the global variable
-			}		//complete
-		state=0;
-}
-if(state>2 && state<8)			//in the valid range to add to the checksum
-{
-	checksum_1+=c;
-	checksum_2+=checksum_1;
 }
-else
+</code>
+===== header =====
+<code c>typedef unsigned char u08;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef int32_t s32;
+typedef struct
 {
-	checksum_1=0;
+	u32 time;					//milliseconds/week
-	checksum_2=0;
+	s32 vnorth;					//cm/s
-}
+	s32 veast;
+	s32 vdown;
+	s32 longitude;					//degrees/10^-7
+	s32 latitude;
+	s32 altitude;					//height/mm
+	u08 packetflag;					//packetflag lets us see when our packet has been updated
+	u08 status;					//type of fix
+	u08 nosats;					//number of tracked satellites
+} ubx_gps_type;
+#define REQUIRED_DATA 0x0F
+#define LLH_DATA 0x02
+#define VELNED_DATA 0x12
+#define SVINFO_DATA 0x30
+#define SOL_DATA 0x06
+#define NAV_CLASS 0x01
+#define SATS_POS 5
+#define SOL_POS 42
+#define POS_OFFSET 40
+#define POS_START 12
+#define POS_END 25
+#define VEL_OFFSET 36
+#define VEL_START 20
+#define VEL_END 37
+#define SYNC_1 0xB5
+#define SYNC_2 0x62
+#define BAUDRATE 38400UL
+#define BAUDDIV 32
+//#define BAUDDIV  (u16)( ((float)F_CPU/(BAUDRATE*16UL)) -1 )//baud divider
+#define TOGGLE_PIN PIND=0x20				//led on port D.5
 </code>