Lcd displaying old data with new data - eclipse-cdt

Question

I have interfaced a programmable xbee with a 16x2 character LCD. I transmit wireless frames with the the help of another xbee and display it on the recieving xbee.
The problem arises when I send two wireless frames one after another.
Consider that I send 24 characters in the first frame, that will be displayed normally as it should be(with a random extra character at the end of the display which I dont know why)
The problem arises when I send a second frame which is smaller than the first frame for eg. of 6 characters. The LCD displays the the 6 characters but adds further 18 characters that were there in the first frame after the 6 characters.
The display looks likes this:
Frame1 display : This is a check message.
Frame2 display : Hello!s a check message. (original message : Hello!)
I tried clearall() lcd function between frames at different positions but it does not work. I also different things you see in the code but they dont work.
The code currently looks like this;
enter code here
#include <xbee_config.h>
#include <types.h>
#include <string.h>
#include <ctype.h>
#define char_lcd_writ_str(a) char_lcd_writ(a, strlen(a))
static uint8_t test_stage = 0;
static uint8_t test_stage_done = 0;
static const char str[] = "abcdefghijklmnopqrstuvwxyz012345";
#if defined(RTC_ENABLE_PERIODIC_TASK)
void rtc_periodic_task(void)
{
test_stage++;
if (test_stage == 8)
test_stage = 0;
test_stage_done = 0;
}
#endif
#ifdef ENABLE_XBEE_HANDLE_RX
int xbee_transparent_rx(const wpan_envelope_t FAR *envelope, void FAR *context)
{
int c=0;
char addrbuf[ADDR64_STRING_LENGTH];
char_lcd_init(CHAR_LCD_CFG);
char_lcd_clear();
addr64_format(addrbuf, &envelope->ieee_address);
sys_watchdog_reset();
while (c<4)
{
char_lcd_writ_str(envelope->payload);
delay_ticks(2*HZ);
char_lcd_clear();
char_lcd_goto_xy(0, 0);
c++;
}
}
#endif
void main(void)
{
uint8_t i, j;
sys_hw_init();
sys_xbee_init();
sys_app_banner();
char_lcd_init(CHAR_LCD_CFG);
for (;;) {
if (!test_stage_done) {
switch (test_stage) {
case 0:
char_lcd_goto_xy(0, 0);
char_lcd_writ_str("All working fine");
break;
}
test_stage_done = 1;
}
sys_watchdog_reset();
sys_xbee_tick();
}
}
ssize_t char_lcd_writ(const uint8_t *data, size_t len)
{
size_t written = 0;
while (written < len) {
char_lcd_putchar(*data++);
written++;
if ( written == 32 || written == 64 || written == 96 || written == 128 || written == 160 || written == 192 )
{
delay_ticks(2*HZ);
char_lcd_clear();
char_lcd_goto_xy(0, 0);
}
}
while (written < len) {
written = 0;
memset(*data++, '\0', len);
written++;
}
return (ssize_t)written;
}

Answer 1

Could be as simple as envelope->payload not being null-terminated and actually containing those extra characters if you go beyond the payload length specified in the envelope. Try using your char_lcd_writ() function with the payload's length instead of char_lcd_writ_str() which will use strlen() to find the length.