Tinkering with a Kospet ROCK

Here's my "driver" at this point, if anyone wants to give a shot at understanding what's missing.

// Driver for HX3603, see https://github.com/moyitai/5.26-sdk-1.0.2--integrate/blob/master/apps/common/device/hr_sensor/hrs3603.c

var dev = wOS.i2c.bind(0x44); // device I2C address

functionHX3603 (){
var conf_hrs = {
  // Clock
  SAMPLE_RATE : 25, // Hz
  PRF_CLK_NUM : 32000/SAMPLE_RATE,
  // PS1 PRF [0-255]
  PS1_INTERVAL_I2C : 64, // NOTE : 3600 datasheet reco

  // Phase Enable
  HRS_ENABLE : 1,
  PS0_ENABLE : 0,
  PS1_ENABLE : 1,
  TS_ENABLE : 0,

  // Oversampling rate 0:128 1:256 2:512 3:1024
  HRS_PS0_TS_OSR : 3,
  PS1_OSR : 3,

  // LED & pulse delay
  HRS_LED : 1,
  HRS_CKAFE : 1,
  HRS_CKAFE_CYCLE : 50,

  PS1_LED : 1,
  PS1_CKAFE : 1,
  PS1_CKAFE_CYCLE : 50,

  // LED Driver current
  HRS_LEDDR_MSB : 3,
  PS1_LEDDR_MSB : 7,
  LEDDR_LSB : 7,

  // LES SEL ?
  LEDSEL_HRS : 1,
  LEDSEL_PS1 : 2,
  FORCE_LEDSEL : 0,

  RESET_CYCLE : 5,

  // DC signal canceling
  DCCANCEL_HRS_IDAC : 0,
  DCCANCEL_PS1_IDAC : 0,

  // EXT PD (power delivery) // Undocumented
  EXTPD_SEL : 1,
  EXTPD_PS1 : 1,
  EXTPD_HRS : 1,

  // TIA 1 | Integrator 0
  TIA_PS1 : 1,
  TIA_HRS : 1,
  // TIA feedback resistor
  RFSEL_HRS : 6,
  RFSEL_PS1 : 1,
  // Integrator Capacitor ?
  HRS_PS0_TS_INT_CAP : 15,
  PS1_INT_CAP : 15,

  // Clock polatiry ?
  ADC_DATA_CLK_POL : 3,
};
var mode_hrs = 1;
var hrs = {
  dev:dev,
  disable: ()=>{
    dev.writeByte(0x01, 0x01); 
    dev.writeByte(0x02, 0x01); 
    delay(50);
    dev.writeByte(0x1a, 0x13); 
  },
  enable: ()=>{
    var c = conf_hrs;
    dev.writeByte(0x1e, 0x00); 
    // Clock config
    dev.writeByte(0x10, c.PRF_CLK_NUM & 0xff); 
    dev.writeByte(0x11, (c.PRF_CLK_NUM & 0x0f00)>>8); 

    // Phase enable and OSR
    dev.writeByte(0x01, c.TS_ENABLE<<4 | c.PS0_ENABLE <<3 | c.HRS_ENABLE<<2 | c.HRS_PS0_TS_OSR);
    dev.writeByte(0x02, c.PS1_ENABLE<<2 | c.PS1_OSR);
    
    // LED enable and AFE clock enable
    dev.writeByte(0x03, c.HRS_LED<<3 | c.PS1_LED<<2 | c.HRS_CKAFE<<1 | c.PS1_CKAFE); // 00001111 // ?:0000|HRS_LED:1|PS1_LED:1|HRS_CKAFE:1|PS1_CKAFE:1
    dev.writeByte(0x08, c.HRS_CKAFE_CYCLE); // hrs ledontime, 0~255,  led on time = 4*hrsckafe_cycle*0.382us
    dev.writeByte(0x09, c.PS1_CKAFE_CYCLE); // ps1 ledontime, 0~255,  led on time = 4*ps1_ckafe_cycle*0.382us

    // clock reset config 
    dev.writeByte(0x04, c.RESET_CYCLE); // 00000101 // 3 bit RESET CYCLE sel //  (2^(reset_cycle+1))-1*/

    // PRF
    dev.writeByte(0x1c, c.PS1_INTERVAL_I2C); // PS1 PRF 0-255 - 25 mean 1s
    dev.writeByte(0x05, c.DCCANCEL_PS1_IDAC); // offset DCCANCEL PS1 
    dev.writeByte(0x06, c.DCCANCEL_HRS_IDAC); // offset DCCANCEL HRS/TS/PS0

    dev.writeByte(0x07, c.LEDSEL_PS1<<4 | c.FORCE_LEDSEL<<3 | LEDSEL_HRS); // 00100010 // ?:0|LEDSEL_PS1:010|FORCE_LEDSEL:0|LEDSEL_HRS:001 
    dev.writeByte(0x0a, c.PS1_INT_CAP<<4 | c.HRS_PS0_TS_INT_CAP); // 11111111 // INTCAPSEL Integrator gain ?

    dev.writeByte(0x0b, c.PS1_LEDDR_MSB<<4 | c.HRS_LEDDR_MSB); // 01110011 // PS1:0111|HRS:0011 LEDDR [0-7]

    dev.writeByte(0xc4, c.EXTPD_SEL<<7 | (c.LEDDR_LSB&0x07)<<4 | 0x0f); // 11111111 // extpd_sel | leddr_lsb | 0x0f

    dev.writeByte(0x0d, c.RFSEL_HRS <<4 | c.RFSEL_PS1); // 01100001 // rfsel_hrs | rfsel_ps1
    dev.writeByte(0x0c, c.RFSEL_PS1); // 00000001 // rfsel_ps1 feedback resistor ?
    dev.writeByte(0x0f, 0x00); // 
    dev.writeByte(0x0e, c.EXTPD_PS1<<3 | c.EXTPD_HRS<<2 | c.TIA_PS1<<1 | c.TIA_HRS); // 00001111 extpd_ps1:1 | extpd_hrs:1 | tia_ps1:1 | tia_hrs:1

    dev.writeByte(0x1b, 0x7f); //
    dev.writeByte(0xc2, 0x10); // Self test
    dev.writeByte(0xc3, 0xff); //
    dev.writeByte(0x18, c.ADC_DATA_CLK_POL); // adc_data_clk_pol

    dev.writeByte(0x1a, 0x12); // 
    dev.writeByte(0x13, 0x02); // enable mode (ps1|hrs)
    dev.writeByte(0x12, 0x50); //
    dev.writeByte(0x20, 0x20); // close fifo int
  },
  read_hrs:()=>{
    var data = dev.readBytes(0xa0,12);
    var p0 = (data[0]) | (data[1]<<8) | (data[2]<<16);
    var p1 = (data[3]) | (data[4]<<8) | (data[5]<<16);
    return { als:[p0, p1], hrs: (p0>p1)?p0-p1:0};
  }
};
return hrs;
}

And here's the module I use it with

var correlator = function(cspan) {
  var CMIN = 7; var CMAX = 37; var NSLOT = 128;
  var buffer = new Array(NSLOT); var next=0;
  cspan = cspan || 1;
  return {
    put: (v)=>{ buffer[next] = v; next = (next+1)%NSLOT; },
    get bpm(){
      var minCorr=0x7FFFFFFF;
      var span=0;
      for (var c=CMIN; c<CMAX; c++) {
        var s = 0; var a = (next-c*cspan) % NSLOT; var b = next;
        for (var i=0; i<(NSLOT-CMAX);i++){
          var d = buffer[b]-buffer[a];
          b = (b+1)%NSLOT; a = (a+1)%NSLOT;
          s += d*d;
        }
        if (s<minCorr) {minCorr = s; span = c;}
      }
      return span == 0 ? 0:(60000/(span*40));
    }
  };
};

function hrm(){
  var corr = correlator();
  var iv;
  var hrm = {
    read:()=>{
      var v = wOS.hrs.read_hrs();
      corr.put(v.hrs);
    },
    start: (record)=>{
      if (iv) return;
      wOS.hrs.enable();
      iv = setInterval(hrm.read, 40);
    },
    stop: ()=>{
      if (!iv) return;
      iv = clearInterval(iv);
      wOS.hrs.disable();
    },
    get bpm() { return corr.bpm(); },
  };
  return hrm;
}