MPR121 workswith touch but not when acting as a liquid level sensor

i trying achieve liquid level indicator mpr 121 , followed https://www.youtube.com/watch?v=pjjmqwqgqdm

it worked when manually touch copper plates when adding water, not detect levels. here config

code: [select]

//============ device address
// add pin vcc address 0x5b
#define mpr121_addr 0x5b


// mpr121 register defines
#define e0bv 0x1e
#define e1bv 0x1f
#define e2bv 0x20
#define e3bv 0x21
#define e4bv 0x22
#define e5bv 0x23
#define e6bv 0x24
#define e7bv 0x25
#define e8bv 0x26
#define e9bv 0x27
#define e10bv 0x28
#define e11bv 0x29
#define e12bv 0x2a


#define mhd_r 0x2b
#define nhd_r 0x2c
#define ncl_r 0x2d
#define fdl_r 0x2e
#define mhd_f 0x2f
#define nhd_f 0x30
#define ncl_f 0x31
#define fdl_f 0x32


#define ele0_t 0x41
#define ele0_r 0x42
#define ele1_t 0x43
#define ele1_r 0x44
#define ele2_t 0x45
#define ele2_r 0x46
#define ele3_t 0x47
#define ele3_r 0x48
#define ele4_t 0x49
#define ele4_r 0x4a
#define ele5_t 0x4b
#define ele5_r 0x4c
#define ele6_t 0x4d
#define ele6_r 0x4e
#define ele7_t 0x4f
#define ele7_r 0x50
#define ele8_t 0x51
#define ele8_r 0x52
#define ele9_t 0x53
#define ele9_r 0x54
#define ele10_t 0x55
#define ele10_r 0x56
#define ele11_t 0x57
#define ele11_r 0x58


#define afe1_cfg 0x5c
#define afe2_cfg 0x5d
#define ele_cfg 0x5e


#define gpio_ctrl0 0x73
#define gpio_ctrl1 0x74
#define gpio_data 0x75
#define gpio_dir 0x76
#define gpio_en 0x77
#define gpio_set 0x78
#define gpio_clear 0x79
#define gpio_toggle 0x7a


#define ato_cfg0 0x7b
#define ato_cfgu 0x7d
#define ato_cfgl 0x7e
#define ato_cfgt 0x7f
#define res_cf          0x80

// global constants //隔住阻焊层
#define tou_thresh 0x06
#define rel_thresh 0x03
#define start_bv 0x90
// global constants //隔住0.5mm
//#define tou_thresh 0x06
//#define rel_thresh 0x03

code: [select]

void mpr121::begin(void){
// stop
mpwrite(ele_cfg, 0x00);
        mpwrite(res_cf, 0x63);
        delay(10);
// section a
// group controls filtering when data > baseline.
mpwrite(mhd_r, 0x01);
mpwrite(nhd_r, 0x01);
mpwrite(ncl_r, 0x00);
mpwrite(fdl_r, 0x00);

// section b
// group controls filtering when data < baseline.
mpwrite(mhd_f, 0x01);
mpwrite(nhd_f, 0x01);
mpwrite(ncl_f, 0xff);
mpwrite(fdl_f, 0x02);

// section c
// group sets touch , release thresholds each electrode
mpwrite(ele0_t, tou_thresh);
mpwrite(ele0_r, rel_thresh);
mpwrite(ele1_t, tou_thresh);
mpwrite(ele1_r, rel_thresh);
mpwrite(ele2_t, tou_thresh);
mpwrite(ele2_r, rel_thresh);
mpwrite(ele3_t, tou_thresh);
mpwrite(ele3_r, rel_thresh);
mpwrite(ele4_t, tou_thresh);
mpwrite(ele4_r, rel_thresh);
mpwrite(ele5_t, tou_thresh);
mpwrite(ele5_r, rel_thresh);
mpwrite(ele6_t, tou_thresh);
mpwrite(ele6_r, rel_thresh);
mpwrite(ele7_t, tou_thresh);
mpwrite(ele7_r, rel_thresh);
mpwrite(ele8_t, tou_thresh);
mpwrite(ele8_r, rel_thresh);
mpwrite(ele9_t, tou_thresh);
mpwrite(ele9_r, rel_thresh);
mpwrite(ele10_t, tou_thresh);
mpwrite(ele10_r, rel_thresh);
mpwrite(ele11_t, tou_thresh);
mpwrite(ele11_r, rel_thresh);

// section d
// set filter configuration
// set esi2
mpwrite(afe1_cfg, 0x10);
//afe配置1 （默认=0x10）
// 一级采样ffi:00-6次
// 充放电电流cdc:100000 - 32ua
mpwrite(afe2_cfg, 0x04);
//afe配置2 （默认=0x24）
// 充电时间cdt:010 - 1us
// 二级采样sfi:00 - 4次
// 二级采样间隔esi:100 - 16ms


// section e
// electrode configuration
// enable 6 electrodes , set run mode
// set ele_cfg 0x00 return standby mode
mpwrite(ele_cfg, 0x8c); // enables 12 electrodes

//afe配置1
// cl
// eleprox
// ele:
// section f
// enable auto config , auto reconfig
/*mpwrite(ato_cfg0, 0x0b);
mpwrite(ato_cfgu, 0xc9); // usl = (vdd-0.7)/vdd*256 = 0xc9 @3.3v   mpwrite(ato_cfgl, 0x82); // lsl = 0.65*usl = 0x82 @3.3v
mpwrite(ato_cfgt, 0xb5);*/ // target = 0.9*usl = 0xb5 @3.3v
}

code: [select]

int mpr121::touch(void)
{
   wire.requestfrom((uint8_t)mpr121_addr,(uint8_t)2); 
   uint8_t a,b;
   if(wire.available()>=2)    // slave may send less requested
   {
#if defined(arduino) && arduino >= 100
     a = wire.read(); // receive byte character
     b = wire.read();
#else
     a = wire.receive(); // receive byte character
     b = wire.receive();
#endif
     return (a | (int)(b<<8));
   }else
   {
     return 0;
   }   
}


here arduino code

code: [select]

#include <mpr121.h>
#include <wire.h>


int irqpin = 2; // digital 2
boolean touchstates[12]; //to keep track of previous touch states
int prev = -1;
int tvar = -1;

void setup() {
  serial.begin(19200);
  wire.begin();
  capatouch.begin(); // calls begin above
  delay(500);
  serial.println("start"); 
}

void loop()
{
  int var = capatouch.touch(); // calls touch defined above
  int num = getsensornumber(var);

  if(num != -1 && num != prev)
  {
    serial.print("num: ");
    serial.println(num);
    prev = num;
  } 
}

int getsensornumber(int var)
{
   if ((var&0x0800) >0) return 12;
   if ((var&0x0400) >0) return 11;
   if ((var&0x0200) >0) return 10;
   if ((var&0x0100) >0) return 9;
   if ((var&0x0080) >0) return 8;
   if ((var&0x0040) >0) return 7;
   if ((var&0x0020) >0) return 6;
   if ((var&0x0010) >0) return 5;
   if ((var&0x0008) >0) return 4;
   if ((var&0x0004) >0) return 3;
   if ((var&0x0002) >0) return 2;
   if ((var&0x0001) >0) return 1;
  return -1;
}

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