After a bunch of tweaking and debugging, I have found no valid reason for why I'm getting a ton of random "blips" when I read in an AnalogIn pin. By a "ton" I mean, ranging from every 60ms to 200 ms apart, but consecutive "blips" are never the same interval apart.
Even when NO SIGNAL is attached to the pin, the mbed still detects a few 1.0's or .99's, even some other values. The blips are not periodic and do not hold a constant value. They show up when I do an AnalogIn read followed by an immediate AnalogOut write. They show up when I write the read value to the filesystem or output through serial.
They go away when I comment out the "sample.read()" command. assigning a value to my input buffer, and then assigning that value to an AnalogOut pin does not cause these blips.
Here's my code. It's real simple, read in a value from an AnalogIn pin, at a certain sampling frequency (3000Hz) and output that read value.
The output DOES look like the input signal, but with this bizarre added "noise".
#include "mbed.h"
AnalogOut mout0(p18);
AnalogIn signal(p16);
Ticker sample;
signed int i;
signed int j;
double count=1;
char tog=0;
static float xin[taps];
LocalFileSystem local("local");
Serial pc(USBTX, USBRX);
void Take_sample();
int main() {
sample.attach_us(&Take_sample,333);
pc.baud(921600);
//FILE *fp = fopen("/local/out.txt", "w"); // Open "out.txt" on the local file system for writing
//fprintf(fp, "Analog Input Trial\n\n");
while (1) {
if (tog==1) {
/* if(count>50000)
break;
else
fprintf(fp, "%.4f\n",xin[0]);*/
tog = 0;
}
}
//fprintf(fp, "\n\nEnd of File.");
//fclose(fp);
return 0;
}
void Take_sample() {
if (tog==0) {
count++;
xin[0] = signal.read();
mout0=xin[0];
tog = 1;
}
}
Michael Mensinger.
2
replies
After a bunch of tweaking and debugging, I have found no valid reason for why I'm getting a ton of random "blips" when I read in an AnalogIn pin. By a "ton" I mean, ranging from every 60ms to 200 ms apart, but consecutive "blips" are never the same interval apart.
Even when NO SIGNAL is attached to the pin, the mbed still detects a few 1.0's or .99's, even some other values. The blips are not periodic and do not hold a constant value. They show up when I do an AnalogIn read followed by an immediate AnalogOut write. They show up when I write the read value to the filesystem or output through serial.
They go away when I comment out the "sample.read()" command. assigning a value to my input buffer, and then assigning that value to an AnalogOut pin does not cause these blips.
Here's my code. It's real simple, read in a value from an AnalogIn pin, at a certain sampling frequency (3000Hz) and output that read value.
The output DOES look like the input signal, but with this bizarre added "noise".
#include "mbed.h" AnalogOut mout0(p18); AnalogIn signal(p16); Ticker sample; signed int i; signed int j; double count=1; char tog=0; static float xin[taps]; LocalFileSystem local("local"); Serial pc(USBTX, USBRX); void Take_sample(); int main() { sample.attach_us(&Take_sample,333); pc.baud(921600); //FILE *fp = fopen("/local/out.txt", "w"); // Open "out.txt" on the local file system for writing //fprintf(fp, "Analog Input Trial\n\n"); while (1) { if (tog==1) { /* if(count>50000) break; else fprintf(fp, "%.4f\n",xin[0]);*/ tog = 0; } } //fprintf(fp, "\n\nEnd of File."); //fclose(fp); return 0; } void Take_sample() { if (tog==0) { count++; xin[0] = signal.read(); mout0=xin[0]; tog = 1; } }