If the Filter is used by the MCU for several times, the output is abnormal

[allrobot]

If the loop runs only one simulated pin and uses a filter, it will output normally (analog 1600~2200, filter 0~500), but creating an array to store multiple filtered simulated pin values will cause problems, and the output will be abnormal (10000~80000).

If analog read six sensors, and their value is 1600~2200.

It used the code below.

#include "EMGFilters.h"
#define SERIAL_TX_BUFFER_SIZE 4096 //修改串口接收缓冲区大小为2048
const int SensorInputPin[] = {A0, A1, A2, A3, A4, A5};
EMGFilters myFilter[6];
SAMPLE_FREQUENCY sampleRate = SAMPLE_FREQ_500HZ;
NOTCH_FREQUENCY humFreq = NOTCH_FREQ_50HZ;

void setup()
{

    for (int i = 0; i < 6; i++)
    {
        myFilter[i].init(sampleRate, humFreq, true, true, true);
    }
    Serial.begin(115200);
    Serial1.begin(250000);
    analogReadResolution(12);
}
void loop()
{
    long time = millis();
    int x[6] = {0,0,0,0,0,0};
    int analog[6] = {0,0,0,0,0,0};

    for (int index = 0; index < 6; index++)
    {
        //x[index] = myFilter[index].update(analogRead(SensorInputPin[index]));
        analog[index] = analogRead(SensorInputPin[index]);
    }
    while ((millis() - time) < 2)
    {
        delayMicroseconds(100);
    }
    Serial.printf("filter:%d %d %d %d %d %d analog:%d %d %d %d %d %d\n", x[0], x[1], x[2], x[3], x[4], x[5],analog[0],analog[1],analog[2],analog[3],analog[4],analog[5]);
    Serial1.printf("<%d,%d,%d,%d,%d,%d>", x[0], x[1], x[2], x[3], x[4], x[5]);
}

Change index<6 to index<2, and uncomment \\x[index] = myFilter[index].update(analogRead(SensorInputPin[index]));

It will be a normal output using two inputs and filters.

But changing index=0;index<2 to index=0;index<6 will be abnormal output.

If changing to index=3;index<4 or index=2;index<3...etc, it will be normal output:

I use two MCUS, both raise the same abnormal.

How do I allow multiple filters to output normally?

[edgar-bonet]

The problem is that the state of the EMGFilters filters is stored in the global variables LPF, HPF and AHF. These being globals means that all instances of EMGFilters share their internal state.

The filter state should be stored as instance data. Otherwise all instances effectively share the same filter.

[edgar-bonet]

@allrobot: I don't understand why you closed the issue. It is still relevant and has not been fixed.