GPS data is lost during reading

Hello Basawaraj,

No code for inspection?

Regards
Amit

Need to concur with Amit - presenting code would be helpful.

But also, you need to get a grip on the characteristics on GPS transmissions via serial line (I assume NMEA 183 ASCII format).

• sentences have a variable length
• a sentence has a fixed/defined start character ($) and termination character(s) (\r\n)
• transmissions use to come in bursts - at the defined update rate, all enabled sentences are sent in short succession

For my application using GPS (NMEA 183, mostly on a competitor's MCU), I used the following strategy:

• single character UART reception interrupt
• reception into a buffer sufficient for the longest possible sentence (e.g. 128 byte)
• on buffer size overflow, reset index pointer to zero (avoid overflow)
• on sentence start character ($), reset index to zero
• on 'normal' characters, store and advance index pointer
• on termination character, check for proper start character, and copy sentence to another buffer for parsing, and set a 'ready' flag

The last step is important. Otherwise, the next transmission will start to overwrite your buffer while you about to parse it. Remember, those sentences come in bursts. I never do the parsing in the interrupt routine - otherwise you will lose character of following sentences, and thus the whole sentence. Instead, I check a flag in the main application loop, and enter parsing as soon as the interrupt routine reports an available sentence. Except for the proper start/termination character, I do no further syntax checking in the interrupt.

For the parsing of NMEA 183, there should be plenty of examples around - just ask your favourite search engine. That is not really TM4C specific. You may, however, need to make a choice how much "library support" you want to pull in (for string/integer number/ float number parsing), and what you want to write yourself, to safe Flash memory space.

No code for inspection...(i.e. DO my homework...all of it...NOW... ... ... of course...it's urgent)

As always - if such posters do NOT need their homework done/completed - they (surely) require Guidance!

Hello,
Below is my code for Recieving GPS data but i am getting only '$' character remaining characters are lossing please help me
#include <stdint.h>
#include <stdbool.h>
//#include "stdlib.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "inc/hw_uart.h"
#include "inc/hw_gpio.h"
//#include "inc/hw_pwm.h"
#include "inc/hw_types.h"
#include "driverlib/adc.h"
#include "driverlib/timer.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/pin_map.h"
//#include "driverlib/rom.h"
#include "driverlib/rom_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "driverlib/ssi.h"
#include "driverlib/systick.h"
#include "driverlib/adc.h"
#include "utils/uartstdio.h"
#include "utils/uartstdio.c"
#include<inc/tm4c129xnczad.h>
#define GPIO_PA0_U0RX 0x00000001
#define GPIO_PA1_U0TX 0x00000401


void printchar( char c);
char readchar();
void printstring(char *string);

int main()
{
int c;
char s[30];
char *string;
int i=0;
SYSCTL_RCGCUART_R|=(1<<0);
SYSCTL_RCGCGPIO_R=(1<<0); //enable clock to porta gpio
GPIO_PORTA_AHB_AFSEL_R=(1<<1)|(1<<0);
GPIO_PORTA_AHB_PCTL_R=(1<<0)|(1<<4);
GPIO_PORTA_AHB_DEN_R=(1<<0)|(1<<1);
UART0_IFLS_R=(0x4<<2);
//UART0_IFLS_R
UART0_CTL_R|=(1<<4);
UART0_CTL_R&=~(1<<0);
UART0_IBRD_R=104;
UART0_FBRD_R=11;
UART0_LCRH_R=(0x3<<5);
UART0_CC_R=0X0;
UART0_CTL_R=(1<<0)|(1<<8)|(1<<9);
SYSCTL_RCGCGPIO_R |=(1<<14);
GPIO_PORTQ_DIR_R=(1<<7)|(1<<4);
GPIO_PORTQ_DEN_R=(1<<7)|(1<<4);
GPIO_PORTQ_DATA_R &=~(1<<7)|(1<<4);
printstring("enter \"r\",\"g\",or \"b\":\n\r");
while(1)
{
for(i=0;i<10 && (c=readchar())!='\n';i++)
{
s[i]=c;
}
if(c=='\n')
{
s[i]='\0';
}
string=s;
printstring(s);
//printchar(c);


switch(c)
{
case 'r':
GPIO_PORTQ_DATA_R=(1<<7); //red led on
break;
case 'g':
GPIO_PORTQ_DATA_R=(1<<4);
break;
case 'b':
GPIO_PORTQ_DATA_R=(1<<7);
break;
case 'A':
GPIO_PORTQ_DATA_R=(1<<4);
break;
case '*':
GPIO_PORTQ_DATA_R=(1<<7);
break;
default:
GPIO_PORTQ_DATA_R=~((1<<7)|(1<<4));
break;
}
}
}



char readchar(void)
{
char c;
while((UART0_FR_R &(1<<4))!=0);

c=UART0_DR_R;

return c;
}
void printchar(char c)
{
while((UART0_FR_R &(1<<5))!=0);

UART0_DR_R=c;

}

void printstring(char *string)
{
while(*string!='\0')
{
printchar(*(string++));
}
}

Hello Amit,
Below is my code for Recieving GPS data but i am getting only '$' character remaining characters are lossing please help me
#include <stdint.h>
#include <stdbool.h>
//#include "stdlib.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "inc/hw_uart.h"
#include "inc/hw_gpio.h"
//#include "inc/hw_pwm.h"
#include "inc/hw_types.h"
#include "driverlib/adc.h"
#include "driverlib/timer.h"
#include "driverlib/gpio.h"
#include "driverlib/interrupt.h"
#include "driverlib/pin_map.h"
//#include "driverlib/rom.h"
#include "driverlib/rom_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "driverlib/ssi.h"
#include "driverlib/systick.h"
#include "driverlib/adc.h"
#include "utils/uartstdio.h"
#include "utils/uartstdio.c"
#include<inc/tm4c129xnczad.h>
#define GPIO_PA0_U0RX 0x00000001
#define GPIO_PA1_U0TX 0x00000401


void printchar( char c);
char readchar();
void printstring(char *string);

int main()
{
int c;
char s[30];
char *string;
int i=0;
SYSCTL_RCGCUART_R|=(1<<0);
SYSCTL_RCGCGPIO_R=(1<<0); //enable clock to porta gpio
GPIO_PORTA_AHB_AFSEL_R=(1<<1)|(1<<0);
GPIO_PORTA_AHB_PCTL_R=(1<<0)|(1<<4);
GPIO_PORTA_AHB_DEN_R=(1<<0)|(1<<1);

UART0_CTL_R|=(1<<4);
UART0_CTL_R&=~(1<<0);
UART0_IBRD_R=104;
UART0_FBRD_R=11;
UART0_LCRH_R=(0x3<<5);
UART0_CC_R=0X0;
UART0_CTL_R=(1<<0)|(1<<8)|(1<<9);
SYSCTL_RCGCGPIO_R |=(1<<14);
GPIO_PORTQ_DIR_R=(1<<7)|(1<<4);
GPIO_PORTQ_DEN_R=(1<<7)|(1<<4);
GPIO_PORTQ_DATA_R &=~(1<<7)|(1<<4);
printstring("enter \"r\",\"g\",or \"b\":\n\r");
while(1)
{
for(i=0;i<10 && (c=readchar())!='\n';i++)
{
s[i]=c;
}
if(c=='\n')
{
s[i]='\0';
}
string=s;
printstring(s);
//printchar(c);


switch(c)
{
case 'r':
GPIO_PORTQ_DATA_R=(1<<7); //red led on
break;
case 'g':
GPIO_PORTQ_DATA_R=(1<<4);
break;
case 'b':
GPIO_PORTQ_DATA_R=(1<<7);
break;
case 'A':
GPIO_PORTQ_DATA_R=(1<<4);
break;
case '*':
GPIO_PORTQ_DATA_R=(1<<7);
break;
default:
GPIO_PORTQ_DATA_R=~((1<<7)|(1<<4));
break;
}
}
}



char readchar(void)
{
char c;
while((UART0_FR_R &(1<<4))!=0);

c=UART0_DR_R;

return c;
}
void printchar(char c)
{
while((UART0_FR_R &(1<<5))!=0);

UART0_DR_R=c;

}

void printstring(char *string)
{
while(*string!='\0')
{
printchar(*(string++));
}
}

Hello Basavaraj,

DRM is not a recommended method at it brings a lot of ambiguity. I would have expected a TivaWare based approach so that the system clock is defined correctly and so do all the settings of the device.

Regards
Amit

Hi,
Please suggest me the appropriate tivaware based tutorials for UART

Hello Baswaraj,

You can refer to the TivaWare Peripheral DriverLib User Guide in TivaWare software installation and the examples in D:\ti\TivaWare_C_Series-2.1.2.111\examples\peripherals\uart

Regards
Amit

Thanks for suggestion

Hello Amit,
While debugging tivaware UART example i am getting following error Please help for the issue
Can't find a source file at "/tmp/TI_MKLIBw9rtfe/SRC/_lock.c"

Hello Baswaraj,

I have never seen that issue. Can you make sure that the driverlib.lib is recompiled and then resulting output linked to your project.

Regards
Amit