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Topic: MPR121 workswith touch but not when acting as a liquid level sensor (Read 124 times) previous topic - next topic


I was trying to achieve liquid level indicator with mpr 121 and followed https://www.youtube.com/watch?v=PJJmQwqGQDM

it worked when i manually touch the copper plates but when adding water, it does not detect the levels. Here is my config

Code: [Select]
//============ Device Address
// ADD pin is Vcc So address is 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){
mpwrite(ELE_CFG, 0x00);
        mpwrite(RES_CF, 0X63);
// Section A
// This group controls filtering when data is > baseline.
mpwrite(MHD_R, 0x01);
mpwrite(NHD_R, 0x01);
mpwrite(NCL_R, 0x00);
mpwrite(FDL_R, 0x00);

// Section B
// This group controls filtering when data is < baseline.
mpwrite(MHD_F, 0x01);
mpwrite(NHD_F, 0x01);
mpwrite(NCL_F, 0xFF);
mpwrite(FDL_F, 0x02);

// Section C
// This group sets touch and release thresholds for 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 the 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 and set to run mode
// Set ELE_CFG to 0x00 to return to standby mode
mpwrite(ELE_CFG, 0x8C); // Enables all 12 Electrodes

// CL
// ELE:
// Section F
// Enable Auto Config and 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)
   uint8_t a,b;
   if(Wire.available()>=2)    // slave may send less than requested
#if defined(ARDUINO) && ARDUINO >= 100
     a = Wire.read(); // receive a byte as character
     b = Wire.read();
     a = Wire.receive(); // receive a byte as character
     b = Wire.receive();
     return (a | (int)(b<<8));
     return 0;

Here is the arduino code

Code: [Select]
#include <mpr121.h>
#include <Wire.h>

int irqpin = 2; // Digital 2
boolean touchStates[12]; //to keep track of the previous touch states
int prev = -1;
int tVar = -1;

void setup() {
  CapaTouch.begin(); // this calls the begin above

void loop()
  int var = CapaTouch.touch(); // this calls touch defined above
  int num = GetSensorNumber(var);

  if(num != -1 && num != prev)
    Serial.print("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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