I’m trying to get my Beaglebone Green to read an input from a certain pin, and when that pin sees a 1 to 0 transition (defined in pulse()), then it should set a timer. I want to make my timer like this:
In idle, the timer is set to a TIMER_HOLD
value (900000)
To start the timer, I set it to something lower then TIMER_HOLD.
Then it should decrement (with the timerupdate()
function).
If it reaches 0 or less -which for an unsigned long is higher than TIMER_HOLD – then a trigger action is executed.
To test/debug this, I added: printf("timer 1: %lld n",timer[1]);
And this works perfect… I see this output:
timer 1: 900000
timer 1: 900000
PULSE
timer 1: 5000
timer 1: 4990
timer 1: 4975
<truncated> .
timer 1: 1
timer 1: 1
timer 1: 1
timer 1: 1
timer 1: 1
timer 1: 0
timer 1: 0
timer 1: 0
timer 1: 0
timer 1: 0
timer 1: 0
timer 1: -1
TIMER TRIGGER
timer 1: 900000
timer 1: 900000
timer 1: 900000
timer 1: 900000
This is my c code:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/timeb.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <string.h>
#include "../../BBBio_lib/BBBiolib.h"
#include <linux/kernel.h>
#include <sys/sysinfo.h>
#define INPUT_LEN 65
#define TIMER_HOLD 900000 // ms
void pin2array();
void timerupdate(void);
unsigned char pulse(unsigned char chkin);
unsigned char x,y;
unsigned char input[6][INPUT_LEN];
unsigned long long timer[10];
unsigned long long skew, prevtime, currtime;
int main(void)
{
for (x=0;x<10;x++) timer[x]=TIMER_HOLD;
iolib_init();
while(1)
{
pin2array();
timerupdate();
if (pulse(0))
{
printf("PULSEn");
timer[1]=5000;
}
printf("timer 1: %lld n",timer[1]); //THIS IS THE DEBUG PRINTF !!!
if (timer[1]>TIMER_HOLD)
{
printf("nTIMER TRIGGERn");
timer[1]=TIMER_HOLD;
// usleep(50000);
}
usleep(1); // CPU savings
}
iolib_free();
return(0);
}
void timerupdate(void)
{
struct timeval tv;
gettimeofday(&tv, NULL);
unsigned long long millisecondsSinceEpoch=
(unsigned long long)(tv.tv_sec) * 1000 +
(unsigned long long)(tv.tv_usec) / 1000;
currtime=millisecondsSinceEpoch;
skew=currtime-prevtime;
prevtime=currtime;
for (x=0;x<10;x++)
{
if (timer[x]<TIMER_HOLD) timer[x]-=skew;
}
}
unsigned char pulse(unsigned char chkin)
{
if (input[0][chkin]==0 && input[1][chkin]==1 && input[2][chkin]==1 && input[3][chkin]==1 && input[4][chkin]==1 && input[5][chkin]==1) return 1;
else return 0;
}
void pin2array()
{
for (x=0;x<INPUT_LEN;x++) input[5][x]=input[4][x];
for (x=0;x<INPUT_LEN;x++) input[4][x]=input[3][x];
for (x=0;x<INPUT_LEN;x++) input[3][x]=input[2][x];
for (x=0;x<INPUT_LEN;x++) input[2][x]=input[1][x];
for (x=0;x<INPUT_LEN;x++) input[1][x]=input[0][x];
input[0][0]=(is_high(8,7));
input[0][1]=(is_high(8,8));
input[0][2]=(is_high(8,9));
input[0][3]=(is_high(8,10));
}
now the weird thing:
When I remove the printf("timer 1: %lld n",timer[1]);
then I only see
PULSE
on the output… the timer never triggers….
Any idea what’s happening?
system info:
root@beaglebone:/# uname -na
Linux beaglebone 4.4.9-ti-r25 #1 SMP Thu May 5 23:08:13 UTC 2016 armv7l GNU/Linux
root@beaglebone:/# gcc --version
gcc (Debian 4.9.2-10) 4.9.2
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Answer
I fixed it by reading /proc/uptime instead, then multiplying it by 10 (tenth of a second resolution is sufficient for my program)
I think the original thing didn’t work because of a rounding error, or a conversion float to int…. not sure though